add a few more fw examples

.gitignore

@@ -152,4 +152,5 @@ cmake_install.cmake
 install_manifest.txt
 compile_commands.json
 CTestTestfile.cmake
+*.dump
 

demo_gpio/.gitignore

@@ -0,0 +1 @@
+/Debug/

demo_gpio/bsp/drivers/fe300prci/fe300prci_driver.c

@@ -0,0 +1,252 @@
+// See LICENSE file for license details
+
+#include "platform.h"
+
+#ifdef PRCI_CTRL_ADDR
+#include "fe300prci/fe300prci_driver.h"
+#include <unistd.h>
+
+#define rdmcycle(x)  {				       \
+    uint32_t lo, hi, hi2;			       \
+    __asm__ __volatile__ ("1:\n\t"		       \
+			  "csrr %0, mcycleh\n\t"       \
+			  "csrr %1, mcycle\n\t"	       \
+			  "csrr %2, mcycleh\n\t"		\
+			  "bne  %0, %2, 1b\n\t"			\
+			  : "=r" (hi), "=r" (lo), "=r" (hi2)) ;	\
+    *(x) = lo | ((uint64_t) hi << 32); 				\
+  }
+
+uint32_t PRCI_measure_mcycle_freq(uint32_t mtime_ticks, uint32_t mtime_freq)
+{
+
+  uint32_t start_mtime = CLINT_REG(CLINT_MTIME);
+  uint32_t end_mtime = start_mtime + mtime_ticks + 1;
+
+  // Make sure we won't get rollover.
+  while (end_mtime < start_mtime){
+    start_mtime = CLINT_REG(CLINT_MTIME);
+    end_mtime = start_mtime + mtime_ticks + 1;
+  }
+
+  // Don't start measuring until mtime edge.
+  uint32_t tmp = start_mtime;
+  do {
+    start_mtime = CLINT_REG(CLINT_MTIME);
+  } while (start_mtime == tmp);
+  
+  uint64_t start_mcycle;
+  rdmcycle(&start_mcycle);
+  
+  while (CLINT_REG(CLINT_MTIME) < end_mtime) ;
+  
+  uint64_t end_mcycle;
+  rdmcycle(&end_mcycle);
+  uint32_t difference = (uint32_t) (end_mcycle - start_mcycle);
+
+  uint64_t freq = ((uint64_t) difference * mtime_freq) / mtime_ticks;
+  return (uint32_t) freq & 0xFFFFFFFF;
+  
+}
+ 
+
+void PRCI_use_hfrosc(int div, int trim)
+{
+  // Make sure the HFROSC is running at its default setting
+  // It is OK to change this even if we are running off of it.
+  
+  PRCI_REG(PRCI_HFROSCCFG) = (ROSC_DIV(div) | ROSC_TRIM(trim) | ROSC_EN(1));
+
+  while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0);
+  
+  PRCI_REG(PRCI_PLLCFG) &= ~PLL_SEL(1);
+}
+
+void PRCI_use_pll(int refsel, int bypass,
+			 int r, int f, int q, int finaldiv,
+			 int hfroscdiv, int hfrosctrim)
+{
+  // Ensure that we aren't running off the PLL before we mess with it.
+  if (PRCI_REG(PRCI_PLLCFG) & PLL_SEL(1)) {
+    // Make sure the HFROSC is running at its default setting
+    PRCI_use_hfrosc(4, 16);
+  }
+  
+  // Set PLL Source to be HFXOSC if desired.
+  uint32_t config_value = 0;
+
+  config_value |= PLL_REFSEL(refsel);
+  
+  if (bypass) {
+    // Bypass
+    config_value |= PLL_BYPASS(1);
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // If we don't have an HFXTAL, this doesn't really matter.
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+  } else {
+  
+    // To overclock, use the hfrosc
+    if (hfrosctrim >= 0 && hfroscdiv >= 0) {
+      PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
+    }
+    
+    // Set DIV Settings for PLL
+    
+    // (Legal values of f_REF are 6-48MHz)
+
+    // Set DIVR to divide-by-2 to get 8MHz frequency
+    // (legal values of f_R are 6-12 MHz)
+
+    config_value |= PLL_BYPASS(1);
+    config_value |= PLL_R(r);
+
+    // Set DIVF to get 512Mhz frequncy
+    // There is an implied multiply-by-2, 16Mhz.
+    // So need to write 32-1
+    // (legal values of f_F are 384-768 MHz)
+    config_value |= PLL_F(f);
+
+    // Set DIVQ to divide-by-2 to get 256 MHz frequency
+    // (legal values of f_Q are 50-400Mhz)
+    config_value |= PLL_Q(q);
+
+    // Set our Final output divide to divide-by-1:
+    if (finaldiv == 1){
+      PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+    } else {
+      PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV(finaldiv-1));
+    }
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // Un-Bypass the PLL.
+    PRCI_REG(PRCI_PLLCFG) &= ~PLL_BYPASS(1);
+
+    // Wait for PLL Lock
+    // Note that the Lock signal can be glitchy.
+    // Need to wait 100 us
+    // RTC is running at 32kHz.
+    // So wait 4 ticks of RTC.
+    uint32_t now = CLINT_REG(CLINT_MTIME);
+    while (CLINT_REG(CLINT_MTIME) - now < 4) ;
+    
+    // Now it is safe to check for PLL Lock
+    while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0);
+
+  }
+
+  // Switch over to PLL Clock source
+  PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
+
+  // If we're running off HFXOSC, turn off the HFROSC to
+  // save power.
+  if (refsel) {
+    PRCI_REG(PRCI_HFROSCCFG) &= ~ROSC_EN(1);
+  }
+  
+}
+
+void PRCI_use_default_clocks()
+{
+  // Turn off the LFROSC
+  AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
+
+  // Use HFROSC
+  PRCI_use_hfrosc(4, 16);
+}
+
+void PRCI_use_hfxosc(uint32_t finaldiv)
+{
+  
+  PRCI_use_pll(1, // Use HFXTAL
+	       1, // Bypass = 1
+	       0, // PLL settings don't matter
+	       0, // PLL settings don't matter
+	       0, // PLL settings don't matter
+	       finaldiv,
+	       -1,
+	       -1);
+}
+
+// This is a generic function, which
+// doesn't span the entire range of HFROSC settings.
+// It only adjusts the trim, which can span a hundred MHz or so.
+// This function does not check the legality of the PLL settings
+// at all, and it is quite possible to configure invalid PLL settings
+// this way.
+// It returns the actual measured CPU frequency.
+
+uint32_t PRCI_set_hfrosctrim_for_f_cpu(uint32_t f_cpu, PRCI_freq_target target )
+{
+
+  uint32_t hfrosctrim = 0;
+  uint32_t hfroscdiv = 4;
+  uint32_t prev_trim = 0;
+
+  // In this function we use PLL settings which
+  // will give us a 32x multiplier from the output
+  // of the HFROSC source to the output of the
+  // PLL. We first measure our HFROSC to get the
+  // right trim, then finally use it as the PLL source.
+  // We should really check here that the f_cpu
+  // requested is something in the limit of the PLL. For
+  // now that is up to the user.
+
+  // This will undershoot for frequencies not divisible by 16.
+  uint32_t desired_hfrosc_freq = (f_cpu/ 16);
+
+  PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
+  
+  // Ignore the first run (for icache reasons)
+  uint32_t cpu_freq = PRCI_measure_mcycle_freq(3000, RTC_FREQ);
+
+  cpu_freq = PRCI_measure_mcycle_freq(3000, RTC_FREQ);
+  uint32_t prev_freq = cpu_freq;
+  
+  while ((cpu_freq < desired_hfrosc_freq) && (hfrosctrim < 0x1F)){
+    prev_trim = hfrosctrim;
+    prev_freq = cpu_freq;
+    hfrosctrim ++;
+    PRCI_use_hfrosc(hfroscdiv, hfrosctrim);
+    cpu_freq = PRCI_measure_mcycle_freq(3000, RTC_FREQ);
+  } 
+
+  // We couldn't go low enough
+  if (prev_freq > desired_hfrosc_freq){
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
+    return cpu_freq;
+  }
+  
+  // We couldn't go high enough
+  if (cpu_freq < desired_hfrosc_freq){
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    cpu_freq = PRCI_measure_mcycle_freq(1000, RTC_FREQ);
+    return cpu_freq;
+  }
+
+  // Check for over/undershoot
+  switch(target) {
+  case(PRCI_FREQ_CLOSEST):
+    if ((desired_hfrosc_freq - prev_freq) < (cpu_freq - desired_hfrosc_freq)) {
+      PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    } else {
+      PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, hfrosctrim);
+    }
+    break;
+  case(PRCI_FREQ_UNDERSHOOT):
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, prev_trim);
+    break;
+  default:
+    PRCI_use_pll(0, 0, 1, 31, 1, 1, hfroscdiv, hfrosctrim);
+  }
+
+  cpu_freq =  PRCI_measure_mcycle_freq(1000, RTC_FREQ);
+  return cpu_freq;
+
+}
+
+#endif

demo_gpio/bsp/drivers/fe300prci/fe300prci_driver.h

@@ -0,0 +1,79 @@
+// See LICENSE file for license details
+
+#ifndef _FE300PRCI_DRIVER_H_
+#define _FE300PRCI_DRIVER_H_
+
+__BEGIN_DECLS
+
+#include <unistd.h>
+
+typedef enum prci_freq_target {
+  
+  PRCI_FREQ_OVERSHOOT,
+  PRCI_FREQ_CLOSEST,
+  PRCI_FREQ_UNDERSHOOT
+
+} PRCI_freq_target;
+
+/* Measure and return the approximate frequency of the 
+ * CPU, as given by measuring the mcycle counter against 
+ * the mtime ticks.
+ */
+uint32_t PRCI_measure_mcycle_freq(uint32_t mtime_ticks, uint32_t mtime_freq);
+
+/* Safely switch over to the HFROSC using the given div
+ * and trim settings.
+ */
+void PRCI_use_hfrosc(int div, int trim);
+
+/* Safely switch over to the 16MHz HFXOSC,
+ * applying the finaldiv clock divider (1 is the lowest
+ * legal value).
+ */
+void PRCI_use_hfxosc(uint32_t finaldiv);
+
+/* Safely switch over to the PLL using the given
+ * settings.
+ * 
+ * Note that not all combinations of the inputs are actually
+ * legal, and this function does not check for their
+ * legality ("safely" means that this function won't turn off
+ * or glitch the clock the CPU is actually running off, but
+ * doesn't protect against you making it too fast or slow.)
+ */
+
+void PRCI_use_pll(int refsel, int bypass,
+			 int r, int f, int q, int finaldiv,
+			 int hfroscdiv, int hfrosctrim);
+
+/* Use the default clocks configured at reset.
+ * This is ~16Mhz HFROSC and turns off the LFROSC
+ * (on the current FE310 Dev Platforms, an external LFROSC is 
+ * used as it is more power efficient).
+ */
+void PRCI_use_default_clocks();
+
+/* This routine will adjust the HFROSC trim
+ * while using HFROSC as the clock source, 
+ * measure the resulting frequency, then
+ * use it as the PLL clock source, 
+ * in an attempt to get over, under, or close to the 
+ * requested frequency. It returns the actual measured 
+ * frequency. 
+ *
+ * Note that the requested frequency must be within the 
+ * range supported by the PLL so not all values are 
+ * achievable with this function, and not all 
+ * are guaranteed to actually work. The PLL
+ * is rated higher than the hardware.
+ * 
+ * There is no check on the desired f_cpu frequency, it
+ * is up to the user to specify something reasonable.
+ */
+
+uint32_t PRCI_set_hfrosctrim_for_f_cpu(uint32_t f_cpu, PRCI_freq_target target);
+
+__END_DECLS
+
+#endif
+  

demo_gpio/bsp/drivers/plic/plic_driver.c

@@ -0,0 +1,127 @@
+// See LICENSE for license details.
+
+#include "sifive/devices/plic.h"
+#include "plic/plic_driver.h"
+#include "platform.h"
+#include "encoding.h"
+#include <string.h>
+
+
+// Note that there are no assertions or bounds checking on these
+// parameter values.
+
+void volatile_memzero(uint8_t * base, unsigned int size)
+{
+  volatile uint8_t * ptr;
+  for (ptr = base; ptr < (base + size); ptr++){
+    *ptr = 0;
+  }
+}
+
+void PLIC_init (
+                plic_instance_t * this_plic,
+                uintptr_t         base_addr,
+                uint32_t num_sources,
+                uint32_t num_priorities
+                )
+{
+  
+  this_plic->base_addr = base_addr;
+  this_plic->num_sources = num_sources;
+  this_plic->num_priorities = num_priorities;
+  
+  // Disable all interrupts (don't assume that these registers are reset).
+  unsigned long hart_id = read_csr(mhartid);
+  volatile_memzero((uint8_t*) (this_plic->base_addr +
+                               PLIC_ENABLE_OFFSET +
+                               (hart_id << PLIC_ENABLE_SHIFT_PER_TARGET)),
+                   (num_sources + 8) / 8);
+  
+  // Set all priorities to 0 (equal priority -- don't assume that these are reset).
+  volatile_memzero ((uint8_t *)(this_plic->base_addr +
+                                PLIC_PRIORITY_OFFSET),
+                    (num_sources + 1) << PLIC_PRIORITY_SHIFT_PER_SOURCE);
+
+  // Set the threshold to 0.
+  volatile plic_threshold* threshold = (plic_threshold*)
+    (this_plic->base_addr +
+     PLIC_THRESHOLD_OFFSET +
+     (hart_id << PLIC_THRESHOLD_SHIFT_PER_TARGET));
+
+  *threshold = 0;
+  
+}
+
+void PLIC_set_threshold (plic_instance_t * this_plic,
+			 plic_threshold threshold){
+
+  unsigned long hart_id = read_csr(mhartid);  
+  volatile plic_threshold* threshold_ptr = (plic_threshold*) (this_plic->base_addr +
+                                                              PLIC_THRESHOLD_OFFSET +
+                                                              (hart_id << PLIC_THRESHOLD_SHIFT_PER_TARGET));
+
+  *threshold_ptr = threshold;
+
+}
+  
+
+void PLIC_enable_interrupt (plic_instance_t * this_plic, plic_source source){
+
+  unsigned long hart_id = read_csr(mhartid);
+  volatile uint8_t * current_ptr = (volatile uint8_t *)(this_plic->base_addr +
+                                                        PLIC_ENABLE_OFFSET +
+                                                        (hart_id << PLIC_ENABLE_SHIFT_PER_TARGET) +
+                                                        (source >> 3));
+  uint8_t current = *current_ptr;
+  current = current | ( 1 << (source & 0x7));
+  *current_ptr = current;
+
+}
+
+void PLIC_disable_interrupt (plic_instance_t * this_plic, plic_source source){
+  
+  unsigned long hart_id = read_csr(mhartid);
+  volatile uint8_t * current_ptr = (volatile uint8_t *) (this_plic->base_addr +
+                                                         PLIC_ENABLE_OFFSET +
+                                                         (hart_id << PLIC_ENABLE_SHIFT_PER_TARGET) +
+                                                         (source >> 3));
+  uint8_t current = *current_ptr;
+  current = current & ~(( 1 << (source & 0x7)));
+  *current_ptr = current;
+  
+}
+
+void PLIC_set_priority (plic_instance_t * this_plic, plic_source source, plic_priority priority){
+
+  if (this_plic->num_priorities > 0) {
+    volatile plic_priority * priority_ptr = (volatile plic_priority *)
+      (this_plic->base_addr +
+       PLIC_PRIORITY_OFFSET +
+       (source << PLIC_PRIORITY_SHIFT_PER_SOURCE));
+    *priority_ptr = priority;
+  }
+}
+
+plic_source PLIC_claim_interrupt(plic_instance_t * this_plic){
+  
+  unsigned long hart_id = read_csr(mhartid);
+
+  volatile plic_source * claim_addr = (volatile plic_source * )
+    (this_plic->base_addr +
+     PLIC_CLAIM_OFFSET +
+     (hart_id << PLIC_CLAIM_SHIFT_PER_TARGET));
+
+  return  *claim_addr;
+  
+}
+
+void PLIC_complete_interrupt(plic_instance_t * this_plic, plic_source source){
+  
+  unsigned long hart_id = read_csr(mhartid);
+  volatile plic_source * claim_addr = (volatile plic_source *) (this_plic->base_addr +
+                                                                PLIC_CLAIM_OFFSET +
+                                                                (hart_id << PLIC_CLAIM_SHIFT_PER_TARGET));
+  *claim_addr = source;
+  
+}
+

demo_gpio/bsp/drivers/plic/plic_driver.h

@@ -0,0 +1,51 @@
+// See LICENSE file for licence details
+
+#ifndef PLIC_DRIVER_H
+#define PLIC_DRIVER_H
+
+
+__BEGIN_DECLS
+
+#include "platform.h"
+
+typedef struct __plic_instance_t
+{
+  uintptr_t base_addr;
+
+  uint32_t num_sources;
+  uint32_t num_priorities;
+  
+} plic_instance_t;
+
+typedef uint32_t plic_source;
+typedef uint32_t plic_priority;
+typedef uint32_t plic_threshold;
+
+void PLIC_init (
+                plic_instance_t * this_plic,
+                uintptr_t         base_addr,
+                uint32_t num_sources,
+                uint32_t num_priorities
+                );
+
+void PLIC_set_threshold (plic_instance_t * this_plic,
+			 plic_threshold threshold);
+  
+void PLIC_enable_interrupt (plic_instance_t * this_plic,
+			    plic_source source);
+
+void PLIC_disable_interrupt (plic_instance_t * this_plic,
+			     plic_source source);
+  
+void PLIC_set_priority (plic_instance_t * this_plic,
+			plic_source source,
+			plic_priority priority);
+
+plic_source PLIC_claim_interrupt(plic_instance_t * this_plic);
+
+void PLIC_complete_interrupt(plic_instance_t * this_plic,
+			     plic_source source);
+
+__END_DECLS
+
+#endif

demo_gpio/bsp/env/entry.S

@@ -0,0 +1,97 @@
+// See LICENSE for license details
+
+#ifndef ENTRY_S
+#define ENTRY_S
+
+#include "encoding.h"
+#include "sifive/bits.h"
+
+  .section      .text.entry	
+  .align 2
+  .global trap_entry
+trap_entry:
+  addi sp, sp, -32*REGBYTES
+
+  STORE x1, 1*REGBYTES(sp)
+  STORE x2, 2*REGBYTES(sp)
+  STORE x3, 3*REGBYTES(sp)
+  STORE x4, 4*REGBYTES(sp)
+  STORE x5, 5*REGBYTES(sp)
+  STORE x6, 6*REGBYTES(sp)
+  STORE x7, 7*REGBYTES(sp)
+  STORE x8, 8*REGBYTES(sp)
+  STORE x9, 9*REGBYTES(sp)
+  STORE x10, 10*REGBYTES(sp)
+  STORE x11, 11*REGBYTES(sp)
+  STORE x12, 12*REGBYTES(sp)
+  STORE x13, 13*REGBYTES(sp)
+  STORE x14, 14*REGBYTES(sp)
+  STORE x15, 15*REGBYTES(sp)
+  STORE x16, 16*REGBYTES(sp)
+  STORE x17, 17*REGBYTES(sp)
+  STORE x18, 18*REGBYTES(sp)
+  STORE x19, 19*REGBYTES(sp)
+  STORE x20, 20*REGBYTES(sp)
+  STORE x21, 21*REGBYTES(sp)
+  STORE x22, 22*REGBYTES(sp)
+  STORE x23, 23*REGBYTES(sp)
+  STORE x24, 24*REGBYTES(sp)
+  STORE x25, 25*REGBYTES(sp)
+  STORE x26, 26*REGBYTES(sp)
+  STORE x27, 27*REGBYTES(sp)
+  STORE x28, 28*REGBYTES(sp)
+  STORE x29, 29*REGBYTES(sp)
+  STORE x30, 30*REGBYTES(sp)
+  STORE x31, 31*REGBYTES(sp)
+
+  csrr a0, mcause
+  csrr a1, mepc
+  mv a2, sp
+  call handle_trap
+  csrw mepc, a0
+
+  # Remain in M-mode after mret
+  li t0, MSTATUS_MPP
+  csrs mstatus, t0
+
+  LOAD x1, 1*REGBYTES(sp)
+  LOAD x2, 2*REGBYTES(sp)
+  LOAD x3, 3*REGBYTES(sp)
+  LOAD x4, 4*REGBYTES(sp)
+  LOAD x5, 5*REGBYTES(sp)
+  LOAD x6, 6*REGBYTES(sp)
+  LOAD x7, 7*REGBYTES(sp)
+  LOAD x8, 8*REGBYTES(sp)
+  LOAD x9, 9*REGBYTES(sp)
+  LOAD x10, 10*REGBYTES(sp)
+  LOAD x11, 11*REGBYTES(sp)
+  LOAD x12, 12*REGBYTES(sp)
+  LOAD x13, 13*REGBYTES(sp)
+  LOAD x14, 14*REGBYTES(sp)
+  LOAD x15, 15*REGBYTES(sp)
+  LOAD x16, 16*REGBYTES(sp)
+  LOAD x17, 17*REGBYTES(sp)
+  LOAD x18, 18*REGBYTES(sp)
+  LOAD x19, 19*REGBYTES(sp)
+  LOAD x20, 20*REGBYTES(sp)
+  LOAD x21, 21*REGBYTES(sp)
+  LOAD x22, 22*REGBYTES(sp)
+  LOAD x23, 23*REGBYTES(sp)
+  LOAD x24, 24*REGBYTES(sp)
+  LOAD x25, 25*REGBYTES(sp)
+  LOAD x26, 26*REGBYTES(sp)
+  LOAD x27, 27*REGBYTES(sp)
+  LOAD x28, 28*REGBYTES(sp)
+  LOAD x29, 29*REGBYTES(sp)
+  LOAD x30, 30*REGBYTES(sp)
+  LOAD x31, 31*REGBYTES(sp)
+
+  addi sp, sp, 32*REGBYTES
+  mret
+
+.weak handle_trap
+handle_trap:
+1:
+  j 1b
+	
+#endif

demo_gpio/bsp/env/freedom-e300-hifive1/flash.lds

@@ -0,0 +1,161 @@
+OUTPUT_ARCH( "riscv" )
+
+ENTRY( _start )
+
+MEMORY
+{
+  flash (rxai!w) : ORIGIN = 0x20400000, LENGTH = 512M
+  ram (wxa!ri) : ORIGIN = 0x80000000, LENGTH = 16K
+}
+
+PHDRS
+{
+  flash PT_LOAD;
+  ram_init PT_LOAD;
+  ram PT_NULL;
+}
+
+SECTIONS
+{
+  __stack_size = DEFINED(__stack_size) ? __stack_size : 2K;
+
+  .init           :
+  {
+    KEEP (*(SORT_NONE(.init)))
+  } >flash AT>flash :flash
+
+  .text           :
+  {
+    *(.text.unlikely .text.unlikely.*)
+    *(.text.startup .text.startup.*)
+    *(.text .text.*)
+    *(.gnu.linkonce.t.*)
+  } >flash AT>flash :flash
+
+  .fini           :
+  {
+    KEEP (*(SORT_NONE(.fini)))
+  } >flash AT>flash :flash
+
+  PROVIDE (__etext = .);
+  PROVIDE (_etext = .);
+  PROVIDE (etext = .);
+
+  .rodata         :
+  {
+    *(.rdata)
+    *(.rodata .rodata.*)
+    *(.gnu.linkonce.r.*)
+  } >flash AT>flash :flash
+
+  . = ALIGN(4);
+
+  .preinit_array  :
+  {
+    PROVIDE_HIDDEN (__preinit_array_start = .);
+    KEEP (*(.preinit_array))
+    PROVIDE_HIDDEN (__preinit_array_end = .);
+  } >flash AT>flash :flash
+
+  .init_array     :
+  {
+    PROVIDE_HIDDEN (__init_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.init_array.*) SORT_BY_INIT_PRIORITY(.ctors.*)))
+    KEEP (*(.init_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .ctors))
+    PROVIDE_HIDDEN (__init_array_end = .);
+  } >flash AT>flash :flash
+
+  .fini_array     :
+  {
+    PROVIDE_HIDDEN (__fini_array_start = .);
+    KEEP (*(SORT_BY_INIT_PRIORITY(.fini_array.*) SORT_BY_INIT_PRIORITY(.dtors.*)))
+    KEEP (*(.fini_array EXCLUDE_FILE (*crtbegin.o *crtbegin?.o *crtend.o *crtend?.o ) .dtors))
+    PROVIDE_HIDDEN (__fini_array_end = .);
+  } >flash AT>flash :flash
+
+  .ctors          :
+  {
+    /* gcc uses crtbegin.o to find the start of
+       the constructors, so we make sure it is
+       first.  Because this is a wildcard, it
+       doesn't matter if the user does not
+       actually link against crtbegin.o; the
+       linker won't look for a file to match a
+       wildcard.  The wildcard also means that it
+       doesn't matter which directory crtbegin.o
+       is in.  */
+    KEEP (*crtbegin.o(.ctors))
+    KEEP (*crtbegin?.o(.ctors))
+    /* We don't want to include the .ctor section from
+       the crtend.o file until after the sorted ctors.
+       The .ctor section from the crtend file contains the
+       end of ctors marker and it must be last */
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .ctors))
+    KEEP (*(SORT(.ctors.*)))
+    KEEP (*(.ctors))
+  } >flash AT>flash :flash
+
+  .dtors          :
+  {
+    KEEP (*crtbegin.o(.dtors))
+    KEEP (*crtbegin?.o(.dtors))
+    KEEP (*(EXCLUDE_FILE (*crtend.o *crtend?.o ) .dtors))
+    KEEP (*(SORT(.dtors.*)))
+    KEEP (*(.dtors))
+  } >flash AT>flash :flash
+
+  .lalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data_lma = . );
+  } >flash AT>flash :flash
+
+  .dalign         :
+  {
+    . = ALIGN(4);
+    PROVIDE( _data = . );
+  } >ram AT>flash :ram_init
+
+  .data          :
+  {
+    *(.data .data.*)
+    *(.gnu.linkonce.d.*)
+    . = ALIGN(8);
+    PROVIDE( __global_pointer$ = . + 0x800 );
+    *(.sdata .sdata.*)
+    *(.gnu.linkonce.s.*)
+    . = ALIGN(8);
+    *(.srodata.cst16)
+    *(.srodata.cst8)
+    *(.srodata.cst4)
+    *(.srodata.cst2)
+    *(.srodata .srodata.*)
+  } >ram AT>flash :ram_init
+
+  . = ALIGN(4);
+  PROVIDE( _edata = . );
+  PROVIDE( edata = . );
+
+  PROVIDE( _fbss = . );
+  PROVIDE( __bss_start = . );
+  .bss            :
+  {
+    *(.sbss*)
+    *(.gnu.linkonce.sb.*)
+    *(.bss .bss.*)
+    *(.gnu.linkonce.b.*)
+    *(COMMON)
+    . = ALIGN(4);
+  } >ram AT>ram :ram
+
+  . = ALIGN(8);
+  PROVIDE( _end = . );
+  PROVIDE( end = . );
+
+  .stack ORIGIN(ram) + LENGTH(ram) - __stack_size :
+  {
+    PROVIDE( _heap_end = . );
+    . = __stack_size;
+    PROVIDE( _sp = . );
+  } >ram AT>ram :ram
+}

demo_gpio/bsp/env/freedom-e300-hifive1/init.c

@@ -0,0 +1,238 @@
+#include <stdint.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include "platform.h"
+#include "encoding.h"
+
+extern int main(int argc, char** argv);
+extern void trap_entry();
+
+static unsigned long mtime_lo(void)
+{
+  return *(volatile unsigned long *)(CLINT_CTRL_ADDR + CLINT_MTIME);
+}
+
+#ifdef __riscv32
+
+static uint32_t mtime_hi(void)
+{
+  return *(volatile uint32_t *)(CLINT_CTRL_ADDR + CLINT_MTIME + 4);
+}
+
+uint64_t get_timer_value()
+{
+  while (1) {
+    uint32_t hi = mtime_hi();
+    uint32_t lo = mtime_lo();
+    if (hi == mtime_hi())
+      return ((uint64_t)hi << 32) | lo;
+  }
+}
+
+#else /* __riscv32 */
+
+uint64_t get_timer_value()
+{
+  return mtime_lo();
+}
+
+#endif
+
+unsigned long get_timer_freq()
+{
+  return 32768;
+}
+
+static void use_hfrosc(int div, int trim)
+{
+  // Make sure the HFROSC is running at its default setting
+  PRCI_REG(PRCI_HFROSCCFG) = (ROSC_DIV(div) | ROSC_TRIM(trim) | ROSC_EN(1));
+  while ((PRCI_REG(PRCI_HFROSCCFG) & ROSC_RDY(1)) == 0) ;
+  PRCI_REG(PRCI_PLLCFG) &= ~PLL_SEL(1);
+}
+
+static void use_pll(int refsel, int bypass, int r, int f, int q)
+{
+  // Ensure that we aren't running off the PLL before we mess with it.
+  if (PRCI_REG(PRCI_PLLCFG) & PLL_SEL(1)) {
+    // Make sure the HFROSC is running at its default setting
+    use_hfrosc(4, 16);
+  }
+
+  // Set PLL Source to be HFXOSC if available.
+  uint32_t config_value = 0;
+
+  config_value |= PLL_REFSEL(refsel);
+
+  if (bypass) {
+    // Bypass
+    config_value |= PLL_BYPASS(1);
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // If we don't have an HFXTAL, this doesn't really matter.
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+  } else {
+    // In case we are executing from QSPI,
+    // (which is quite likely) we need to
+    // set the QSPI clock divider appropriately
+    // before boosting the clock frequency.
+
+    // Div = f_sck/2
+    SPI0_REG(SPI_REG_SCKDIV) = 8;
+
+    // Set DIV Settings for PLL
+    // Both HFROSC and HFXOSC are modeled as ideal
+    // 16MHz sources (assuming dividers are set properly for
+    // HFROSC).
+    // (Legal values of f_REF are 6-48MHz)
+
+    // Set DIVR to divide-by-2 to get 8MHz frequency
+    // (legal values of f_R are 6-12 MHz)
+
+    config_value |= PLL_BYPASS(1);
+    config_value |= PLL_R(r);
+
+    // Set DIVF to get 512Mhz frequncy
+    // There is an implied multiply-by-2, 16Mhz.
+    // So need to write 32-1
+    // (legal values of f_F are 384-768 MHz)
+    config_value |= PLL_F(f);
+
+    // Set DIVQ to divide-by-2 to get 256 MHz frequency
+    // (legal values of f_Q are 50-400Mhz)
+    config_value |= PLL_Q(q);
+
+    // Set our Final output divide to divide-by-1:
+    PRCI_REG(PRCI_PLLDIV) = (PLL_FINAL_DIV_BY_1(1) | PLL_FINAL_DIV(0));
+
+    PRCI_REG(PRCI_PLLCFG) = config_value;
+
+    // Un-Bypass the PLL.
+    PRCI_REG(PRCI_PLLCFG) &= ~PLL_BYPASS(1);
+
+    // Wait for PLL Lock
+    // Note that the Lock signal can be glitchy.
+    // Need to wait 100 us
+    // RTC is running at 32kHz.
+    // So wait 4 ticks of RTC.
+    uint32_t now = mtime_lo();
+    while (mtime_lo() - now < 4) ;
+
+    // Now it is safe to check for PLL Lock
+    while ((PRCI_REG(PRCI_PLLCFG) & PLL_LOCK(1)) == 0) ;
+  }
+
+  // Switch over to PLL Clock source
+  PRCI_REG(PRCI_PLLCFG) |= PLL_SEL(1);
+}
+
+static void use_default_clocks()
+{
+  // Turn off the LFROSC
+  AON_REG(AON_LFROSC) &= ~ROSC_EN(1);
+
+  // Use HFROSC
+  use_hfrosc(4, 16);
+}
+
+static unsigned long __attribute__((noinline)) measure_cpu_freq(size_t n)
+{
+  unsigned long start_mtime, delta_mtime;
+  unsigned long mtime_freq = get_timer_freq();
+
+  // Don't start measuruing until we see an mtime tick
+  unsigned long tmp = mtime_lo();
+  do {
+    start_mtime = mtime_lo();
+  } while (start_mtime == tmp);
+
+  unsigned long start_mcycle = read_csr(mcycle);
+
+  do {
+    delta_mtime = mtime_lo() - start_mtime;
+  } while (delta_mtime < n);
+
+  unsigned long delta_mcycle = read_csr(mcycle) - start_mcycle;
+
+  return (delta_mcycle / delta_mtime) * mtime_freq
+         + ((delta_mcycle % delta_mtime) * mtime_freq) / delta_mtime;
+}
+
+unsigned long get_cpu_freq()
+{
+  static uint32_t cpu_freq;
+
+  if (!cpu_freq) {
+    // warm up I$
+    measure_cpu_freq(1);
+    // measure for real
+    cpu_freq = measure_cpu_freq(10);
+  }
+
+  return cpu_freq;
+}
+
+static void uart_init(size_t baud_rate)
+{
+  GPIO_REG(GPIO_IOF_SEL) &= ~IOF0_UART0_MASK;
+  GPIO_REG(GPIO_IOF_EN) |= IOF0_UART0_MASK;
+  UART0_REG(UART_REG_DIV) = get_cpu_freq() / baud_rate - 1;
+  UART0_REG(UART_REG_TXCTRL) |= UART_TXEN;
+}
+
+
+
+#ifdef USE_PLIC
+extern void handle_m_ext_interrupt();
+#endif
+
+#ifdef USE_M_TIME
+extern void handle_m_time_interrupt();
+#endif
+
+uintptr_t handle_trap(uintptr_t mcause, uintptr_t epc)
+{
+  if (0){
+#ifdef USE_PLIC
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_EXT)) {
+    handle_m_ext_interrupt();
+#endif
+#ifdef USE_M_TIME
+    // External Machine-Level interrupt from PLIC
+  } else if ((mcause & MCAUSE_INT) && ((mcause & MCAUSE_CAUSE) == IRQ_M_TIMER)){
+    handle_m_time_interrupt();
+#endif
+  }
+  else {
+    write(1, "trap\n", 5);
+    _exit(1 + mcause);
+  }
+  return epc;
+}
+
+void _init()
+{
+  
+  #ifndef NO_INIT
+  use_default_clocks();
+  use_pll(0, 0, 1, 31, 1);
+  uart_init(115200);
+
+  printf("core freq at %d Hz\n", get_cpu_freq());
+
+  write_csr(mtvec, &trap_entry);
+  if (read_csr(misa) & (1 << ('F' - 'A'))) { // if F extension is present
+    write_csr(mstatus, MSTATUS_FS); // allow FPU instructions without trapping
+    write_csr(fcsr, 0); // initialize rounding mode, undefined at reset
+  }
+  #endif
+  
+}
+
+void _fini()
+{
+}

demo_gpio/bsp/env/freedom-e300-hifive1/openocd.cfg

@@ -0,0 +1,34 @@
+adapter_khz     10000
+
+interface ftdi
+ftdi_device_desc "Dual RS232-HS"
+ftdi_vid_pid 0x0403 0x6010
+
+ftdi_layout_init 0x0008 0x001b
+ftdi_layout_signal nSRST -oe 0x0020 -data 0x0020
+
+#Reset Stretcher logic on FE310 is ~1 second long
+#This doesn't apply if you use
+# ftdi_set_signal, but still good to document
+#adapter_nsrst_delay 1500
+
+set _CHIPNAME riscv
+jtag newtap $_CHIPNAME cpu -irlen 5 -expected-id 0x10e31913
+
+set _TARGETNAME $_CHIPNAME.cpu
+target create $_TARGETNAME riscv -chain-position $_TARGETNAME
+$_TARGETNAME configure -work-area-phys 0x80000000 -work-area-size 10000 -work-area-backup 1
+
+flash bank onboard_spi_flash fespi 0x20000000 0 0 0 $_TARGETNAME
+init
+#reset -- This type of reset is not implemented yet
+if {[ info exists pulse_srst]} {
+  ftdi_set_signal nSRST 0
+  ftdi_set_signal nSRST z
+  #Wait for the reset stretcher
+  #It will work without this, but
+  #will incur lots of delays for later commands.
+  sleep 1500
+}	
+halt
+#flash protect 0 64 last off

demo_gpio/bsp/env/freedom-e300-hifive1/platform.h

@@ -0,0 +1,133 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_PLATFORM_H
+#define _SIFIVE_PLATFORM_H
+
+// Some things missing from the official encoding.h
+#define MCAUSE_INT         0x80000000
+#define MCAUSE_CAUSE       0x7FFFFFFF
+
+#include "sifive/const.h"
+#include "sifive/devices/aon.h"
+#include "sifive/devices/clint.h"
+#include "sifive/devices/gpio.h"
+#include "sifive/devices/otp.h"
+#include "sifive/devices/plic.h"
+#include "sifive/devices/prci.h"
+#include "sifive/devices/pwm.h"
+#include "sifive/devices/spi.h"
+#include "sifive/devices/uart.h"
+
+/****************************************************************************
+ * Platform definitions
+ *****************************************************************************/
+
+// Memory map
+#define MASKROM_MEM_ADDR _AC(0x00001000,UL)
+#define TRAPVEC_TABLE_CTRL_ADDR _AC(0x00001010,UL)
+#define OTP_MEM_ADDR _AC(0x00020000,UL)
+#define CLINT_CTRL_ADDR _AC(0x02000000,UL)
+#define PLIC_CTRL_ADDR _AC(0x0C000000,UL)
+#define AON_CTRL_ADDR _AC(0x10000000,UL)
+#define PRCI_CTRL_ADDR _AC(0x10008000,UL)
+#define OTP_CTRL_ADDR _AC(0x10010000,UL)
+#define GPIO_CTRL_ADDR _AC(0x10012000,UL)
+#define UART0_CTRL_ADDR _AC(0x10013000,UL)
+#define SPI0_CTRL_ADDR _AC(0x10014000,UL)
+#define PWM0_CTRL_ADDR _AC(0x10015000,UL)
+#define UART1_CTRL_ADDR _AC(0x10023000,UL)
+#define SPI1_CTRL_ADDR _AC(0x10024000,UL)
+#define PWM1_CTRL_ADDR _AC(0x10025000,UL)
+#define SPI2_CTRL_ADDR _AC(0x10034000,UL)
+#define PWM2_CTRL_ADDR _AC(0x10035000,UL)
+#define SPI0_MEM_ADDR _AC(0x20000000,UL)
+#define MEM_CTRL_ADDR _AC(0x80000000,UL)
+
+// IOF masks
+#define IOF0_SPI1_MASK          _AC(0x000007FC,UL)
+#define SPI11_NUM_SS     (4)
+#define IOF_SPI1_SS0          (2u)
+#define IOF_SPI1_SS1          (8u)
+#define IOF_SPI1_SS2          (9u)
+#define IOF_SPI1_SS3          (10u)
+#define IOF_SPI1_MOSI         (3u)
+#define IOF_SPI1_MISO         (4u)
+#define IOF_SPI1_SCK          (5u)
+#define IOF_SPI1_DQ0          (3u)
+#define IOF_SPI1_DQ1          (4u)
+#define IOF_SPI1_DQ2          (6u)
+#define IOF_SPI1_DQ3          (7u)
+
+#define IOF0_SPI2_MASK          _AC(0xFC000000,UL)
+#define SPI2_NUM_SS       (1)
+#define IOF_SPI2_SS0          (26u)
+#define IOF_SPI2_MOSI         (27u)
+#define IOF_SPI2_MISO         (28u)
+#define IOF_SPI2_SCK          (29u)
+#define IOF_SPI2_DQ0          (27u)
+#define IOF_SPI2_DQ1          (28u)
+#define IOF_SPI2_DQ2          (30u)
+#define IOF_SPI2_DQ3          (31u)
+
+//#define IOF0_I2C_MASK          _AC(0x00003000,UL)
+
+#define IOF0_UART0_MASK         _AC(0x00030000, UL)
+#define IOF_UART0_RX   (16u)
+#define IOF_UART0_TX   (17u)
+
+#define IOF0_UART1_MASK         _AC(0x03000000, UL)
+#define IOF_UART1_RX (24u)
+#define IOF_UART1_TX (25u)
+
+#define IOF1_PWM0_MASK          _AC(0x0000000F, UL)
+#define IOF1_PWM1_MASK          _AC(0x00780000, UL)
+#define IOF1_PWM2_MASK          _AC(0x00003C00, UL)
+
+// Interrupt numbers
+#define INT_RESERVED 0
+#define INT_WDOGCMP 1
+#define INT_RTCCMP 2
+#define INT_UART0_BASE 3
+#define INT_UART1_BASE 4
+#define INT_SPI0_BASE 5
+#define INT_SPI1_BASE 6
+#define INT_SPI2_BASE 7
+#define INT_GPIO_BASE 8
+#define INT_PWM0_BASE 40
+#define INT_PWM1_BASE 44
+#define INT_PWM2_BASE 48
+
+// Helper functions
+#define _REG32(p, i) (*(volatile uint32_t *) ((p) + (i)))
+#define _REG32P(p, i) ((volatile uint32_t *) ((p) + (i)))
+#define AON_REG(offset) _REG32(AON_CTRL_ADDR, offset)
+#define CLINT_REG(offset) _REG32(CLINT_CTRL_ADDR, offset)
+#define GPIO_REG(offset) _REG32(GPIO_CTRL_ADDR, offset)
+#define OTP_REG(offset)  _REG32(OTP_CTRL_ADDR, offset)
+#define PLIC_REG(offset) _REG32(PLIC_CTRL_ADDR, offset)
+#define PRCI_REG(offset) _REG32(PRCI_CTRL_ADDR, offset)
+#define PWM0_REG(offset) _REG32(PWM0_CTRL_ADDR, offset)
+#define PWM1_REG(offset) _REG32(PWM1_CTRL_ADDR, offset)
+#define PWM2_REG(offset) _REG32(PWM2_CTRL_ADDR, offset)
+#define SPI0_REG(offset) _REG32(SPI0_CTRL_ADDR, offset)
+#define SPI1_REG(offset) _REG32(SPI1_CTRL_ADDR, offset)
+#define SPI2_REG(offset) _REG32(SPI2_CTRL_ADDR, offset)
+#define UART0_REG(offset) _REG32(UART0_CTRL_ADDR, offset)
+#define UART1_REG(offset) _REG32(UART1_CTRL_ADDR, offset)
+
+// Misc
+
+#include <stdint.h>
+
+#define NUM_GPIO 32
+
+#define PLIC_NUM_INTERRUPTS 52
+#define PLIC_NUM_PRIORITIES 7
+
+#include "hifive1.h"
+
+unsigned long get_cpu_freq(void);
+unsigned long get_timer_freq(void);
+uint64_t get_timer_value(void);
+
+#endif /* _SIFIVE_PLATFORM_H */

demo_gpio/bsp/env/hifive1.h

@@ -0,0 +1,81 @@
+// See LICENSE for license details.
+
+#ifndef _SIFIVE_HIFIVE1_H
+#define _SIFIVE_HIFIVE1_H
+
+#include <stdint.h>
+
+/****************************************************************************
+ * GPIO Connections
+ *****************************************************************************/
+
+// These are the GPIO bit offsets for the RGB LED on HiFive1 Board.
+// These are also mapped to RGB LEDs on the Freedom E300 Arty
+// FPGA
+// Dev Kit.
+
+#define RED_LED_OFFSET   22
+#define GREEN_LED_OFFSET 19
+#define BLUE_LED_OFFSET  21
+
+// These are the GPIO bit offsets for the differen digital pins
+// on the headers for both the HiFive1 Board and the Freedom E300 Arty FPGA Dev Kit.
+#define PIN_0_OFFSET 16
+#define PIN_1_OFFSET 17
+#define PIN_2_OFFSET 18
+#define PIN_3_OFFSET 19
+#define PIN_4_OFFSET 20
+#define PIN_5_OFFSET 21
+#define PIN_6_OFFSET 22
+#define PIN_7_OFFSET 23
+#define PIN_8_OFFSET 0
+#define PIN_9_OFFSET 1
+#define PIN_10_OFFSET 2
+#define PIN_11_OFFSET 3
+#define PIN_12_OFFSET 4
+#define PIN_13_OFFSET 5
+//#define PIN_14_OFFSET 8 //This pin is not connected on either board.
+#define PIN_15_OFFSET 9
+#define PIN_16_OFFSET 10
+#define PIN_17_OFFSET 11
+#define PIN_18_OFFSET 12
+#define PIN_19_OFFSET 13
+
+// These are *PIN* numbers, not
+// GPIO Offset Numbers.
+#define PIN_SPI1_SCK    (13u)
+#define PIN_SPI1_MISO   (12u)
+#define PIN_SPI1_MOSI   (11u)
+#define PIN_SPI1_SS0    (10u)
+#define PIN_SPI1_SS1    (14u) 
+#define PIN_SPI1_SS2    (15u)
+#define PIN_SPI1_SS3    (16u)
+
+#define SS_PIN_TO_CS_ID(x) \
+  ((x==PIN_SPI1_SS0 ? 0 :		 \
+    (x==PIN_SPI1_SS1 ? 1 :		 \
+     (x==PIN_SPI1_SS2 ? 2 :		 \
+      (x==PIN_SPI1_SS3 ? 3 :		 \
+       -1))))) 
+
+
+// These buttons are present only on the Freedom E300 Arty Dev Kit.
+#ifdef HAS_BOARD_BUTTONS
+#define BUTTON_0_OFFSET 15
+#define BUTTON_1_OFFSET 30
+#define BUTTON_2_OFFSET 31
+
+#define INT_DEVICE_BUTTON_0 (INT_GPIO_BASE + BUTTON_0_OFFSET)
+#define INT_DEVICE_BUTTON_1 (INT_GPIO_BASE + BUTTON_1_OFFSET)
+#define INT_DEVICE_BUTTON_2 (INT_GPIO_BASE + BUTTON_2_OFFSET)
+
+#endif
+
+#define HAS_HFXOSC 1
+#define HAS_LFROSC_BYPASS 1
+
+#define RTC_FREQ 32768
+
+void write_hex(int fd, unsigned long int hex);
+
+#endif /* _SIFIVE_HIFIVE1_H */

demo_gpio/bsp/env/start.S

@@ -0,0 +1,111 @@
+// See LICENSE for license details.
+#include <sifive/smp.h>
+
+/* This is defined in sifive/platform.h, but that can't be included from
+ * assembly. */
+#define CLINT_CTRL_ADDR 0x02000000
+
+	.section .init
+	.globl _start
+	.type _start,@function
+
+_start:
+	.cfi_startproc
+	.cfi_undefined ra
+.option push
+.option norelax
+	la gp, __global_pointer$
+.option pop
+	la sp, _sp
+
+#if defined(ENABLE_SMP)
+	smp_pause(t0, t1)
+#endif
+
+	/* Load data section */
+	la a0, _data_lma
+	la a1, _data
+	la a2, _edata
+	bgeu a1, a2, 2f
+1:
+	lw t0, (a0)
+	sw t0, (a1)
+	addi a0, a0, 4
+	addi a1, a1, 4
+	bltu a1, a2, 1b
+2:
+
+	/* Clear bss section */
+	la a0, __bss_start
+	la a1, _end
+	bgeu a0, a1, 2f
+1:
+	sw zero, (a0)
+	addi a0, a0, 4
+	bltu a0, a1, 1b
+2:
+
+	/* Call global constructors */
+	la a0, __libc_fini_array
+	call atexit
+	call __libc_init_array
+
+#ifndef __riscv_float_abi_soft
+	/* Enable FPU */
+	li t0, MSTATUS_FS
+	csrs mstatus, t0
+	csrr t1, mstatus
+	and t1, t1, t0
+	beqz t1, 1f
+	fssr x0
+1:
+#endif
+
+#if defined(ENABLE_SMP)
+	smp_resume(t0, t1)
+
+	csrr a0, mhartid
+	bnez a0, 2f
+#endif
+
+	auipc ra, 0
+	addi sp, sp, -16
+#if __riscv_xlen == 32
+	sw ra, 8(sp)
+#else
+	sd ra, 8(sp)
+#endif
+
+	/* argc = argv = 0 */
+	li a0, 0
+	li a1, 0
+	call main
+	tail exit
+1:
+	j 1b
+
+#if defined(ENABLE_SMP)
+2:
+	la t0, trap_entry
+	csrw mtvec, t0
+
+	csrr a0, mhartid
+	la t1, _sp
+	slli t0, a0, 10
+	sub sp, t1, t0
+
+	auipc ra, 0
+	addi sp, sp, -16
+#if __riscv_xlen == 32
+	sw ra, 8(sp)
+#else
+	sd ra, 8(sp)
+#endif
+
+	call secondary_main
+	tail exit
+
+1:
+	j 1b
+#endif
+	.cfi_endproc

demo_gpio/bsp/include/sifive/bits.h

@@ -0,0 +1,36 @@
+// See LICENSE for license details.
+#ifndef _RISCV_BITS_H
+#define _RISCV_BITS_H
+
+#define likely(x) __builtin_expect((x), 1)
+#define unlikely(x) __builtin_expect((x), 0)
+
+#define ROUNDUP(a, b) ((((a)-1)/(b)+1)*(b))
+#define ROUNDDOWN(a, b) ((a)/(b)*(b))
+
+#define MAX(a, b) ((a) > (b) ? (a) : (b))
+#define MIN(a, b) ((a) < (b) ? (a) : (b))