lib: sbi: Implement SBI PMU extension

RISC-V SBI specfication 0.3 defines a PMU extension that allows supervisor
mode to start/stop/configure pmu related events. This patch implements
all of the functionality defined in the specification.

Reviewed-by: Anup Patel <anup.patel@wdc.com>
Signed-off-by: Atish Patra <atish.patra@wdc.com>

include/sbi/sbi_ecall.h

@@ -39,6 +39,7 @@ extern struct sbi_ecall_extension ecall_ipi;
 extern struct sbi_ecall_extension ecall_vendor;
 extern struct sbi_ecall_extension ecall_hsm;
 extern struct sbi_ecall_extension ecall_srst;
+extern struct sbi_ecall_extension ecall_pmu;
 
 u16 sbi_ecall_version_major(void);
 

lib/sbi/objects.mk

@@ -20,6 +20,7 @@ libsbi-objs-y += sbi_ecall.o
 libsbi-objs-y += sbi_ecall_base.o
 libsbi-objs-y += sbi_ecall_hsm.o
 libsbi-objs-y += sbi_ecall_legacy.o
+libsbi-objs-y += sbi_ecall_pmu.o
 libsbi-objs-y += sbi_ecall_replace.o
 libsbi-objs-y += sbi_ecall_vendor.o
 libsbi-objs-y += sbi_emulate_csr.o

lib/sbi/sbi_ecall.c

@@ -162,6 +162,9 @@ int sbi_ecall_init(void)
 	if (ret)
 		return ret;
 	ret = sbi_ecall_register_extension(&ecall_srst);
+	if (ret)
+		return ret;
+	ret = sbi_ecall_register_extension(&ecall_pmu);
 	if (ret)
 		return ret;
 	ret = sbi_ecall_register_extension(&ecall_legacy);

lib/sbi/sbi_ecall_pmu.c

@@ -0,0 +1,93 @@
+/*
+ * SPDX-License-Identifier: BSD-2-Clause
+ *
+ * Copyright (c) 2021 Western Digital Corporation or its affiliates.
+ *
+ * Authors:
+ *   Atish Patra <atish.patra@wdc.com>
+ */
+
+#include <sbi/sbi_ecall.h>
+#include <sbi/sbi_ecall_interface.h>
+#include <sbi/sbi_error.h>
+#include <sbi/sbi_hart.h>
+#include <sbi/sbi_trap.h>
+#include <sbi/sbi_version.h>
+#include <sbi/sbi_pmu.h>
+#include <sbi/sbi_scratch.h>
+#include <sbi/riscv_asm.h>
+
+static int sbi_ecall_pmu_handler(unsigned long extid, unsigned long funcid,
+				 const struct sbi_trap_regs *regs,
+				 unsigned long *out_val,
+				 struct sbi_trap_info *out_trap)
+{
+	int ret = 0;
+	uint64_t temp;
+
+	switch (funcid) {
+	case SBI_EXT_PMU_NUM_COUNTERS:
+		ret = sbi_pmu_num_ctr();
+		if (ret >= 0) {
+			*out_val = ret;
+			ret = 0;
+		}
+		break;
+	case SBI_EXT_PMU_COUNTER_GET_INFO:
+		ret = sbi_pmu_ctr_get_info(regs->a0, out_val);
+		break;
+	case SBI_EXT_PMU_COUNTER_CFG_MATCH:
+#if __riscv_xlen == 32
+		temp = ((uint64_t)regs->a5 << 32) | regs->a4;
+#else
+		temp = regs->a4;
+#endif
+		ret = sbi_pmu_ctr_cfg_match(regs->a0, regs->a1, regs->a2,
+					    regs->a3, temp);
+		if (ret >= 0) {
+			*out_val = ret;
+			ret = 0;
+		}
+
+		break;
+	case SBI_EXT_PMU_COUNTER_FW_READ:
+		ret = sbi_pmu_ctr_read(regs->a0, out_val);
+		break;
+	case SBI_EXT_PMU_COUNTER_START:
+
+#if __riscv_xlen == 32
+		temp = ((uint64_t)regs->a4 << 32) | regs->a3;
+#else
+		temp = regs->a3;
+#endif
+		ret = sbi_pmu_ctr_start(regs->a0, regs->a1, regs->a2, temp);
+		break;
+	case SBI_EXT_PMU_COUNTER_STOP:
+		ret = sbi_pmu_ctr_stop(regs->a0, regs->a1, regs->a2);
+		break;
+	default:
+		ret = SBI_ENOTSUPP;
+	};
+
+	return ret;
+}
+
+static int sbi_ecall_pmu_probe(unsigned long extid, unsigned long *out_val)
+{
+	struct sbi_scratch *scratch = sbi_scratch_thishart_ptr();
+
+	/* SBI PMU extension is useless without mcount inhibit features */
+	if (sbi_hart_has_feature(scratch, SBI_HART_HAS_MCOUNTINHIBIT))
+		*out_val = 1;
+	else
+		*out_val = 0;
+
+	return 0;
+}
+
+struct sbi_ecall_extension ecall_pmu = {
+	.extid_start = SBI_EXT_PMU,
+	.extid_end = SBI_EXT_PMU,
+	.handle = sbi_ecall_pmu_handler,
+	.probe = sbi_ecall_pmu_probe,
+};

lib/sbi/sbi_pmu.c

@@ -375,7 +375,7 @@ static int pmu_update_hw_mhpmevent(struct sbi_pmu_hw_event *hw_evt, int ctr_idx,
 	if (!mhpmevent_val || ctr_idx < 3 || ctr_idx >= SBI_PMU_HW_CTR_MAX)
 		return SBI_EFAIL;
 
-	/* TODO: The upper 8 bits of mhpmevent is reserved by sscofpmf extension.
+	/* TODO: The upper 16 bits of mhpmevent is reserved by sscofpmf extension.
 	 * Update those bits based on the flags received from supervisor.
 	 * The OVF bit also should be cleared here in case it was not cleared
 	 * during event stop.