Commit Graph

514 Commits

Author SHA1 Message Date
Xiang W
5e20d25f19 include: sbi: fix CSR define of mseccfg
Because the CSR names in the spec are mseccfg and mseccfgh. Remove
CSR_MSECCFG_LOWER and CSR_MSECCFG_UPPER and directly define
CSR_MSECCFG and CSR_MSECCFGH.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-31 11:51:49 +05:30
Himanshu Chauhan
6e44ef686a lib: sbi: Add functions to map/unmap shared memory
When Smepmp is enabled, M-mode will need to map/unmap the
shared memory before it can read/write to it. This patch
adds functions to create dynamic short-lived mappings.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:44:02 +05:30
Himanshu Chauhan
5dd8db5b10 lib: sbi: Add support for Smepmp
- If Smepmp is enabled, the access flags of an entry are determined based on
  truth table defined in Smepmp.
- First PMP entry (index 0) is reserved.
- Existing boot PMP entries start from index 1.
- Since enabling Smepmp revokes the access privileges of the M-mode software
  on S/U-mode region, first PMP entry is used to map/unmap the shared memory
  between M and S/U-mode. This allows a temporary access window for the M-mode
  software to read/write to S/U-mode memory region.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:42:09 +05:30
Himanshu Chauhan
d72f5f1747 lib: utils: Add detection of Smepmp from ISA string in FDT
- Add function to parse ISA string in FDT.
- Set Smepmp feature bit in extensions if "smepmp" string is found in ISA string.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:12:58 +05:30
Himanshu Chauhan
cbcfc7b10c lib: sbi: Add smepmp in hart extensions
- Add Smepmp as extension in sbi_hart_extensions enum
- Return "smepmp" string for Smepmp extension from sbi_hart_extension_id2string

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:12:16 +05:30
Himanshu Chauhan
6c202c5efd include: sbi: Add Smepmp specific access flags for PMP entries
Smepmp specification defines a truth table based on which the access is allowed to
different modes. This patch adds different flags based on this truth table.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:11:10 +05:30
Himanshu Chauhan
1c099c4f36 lib: sbi: Add functions to manipulate PMP entries
- Add a function to disable a given PMP entry.
- Add a function to check if a given entry is disabled.

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:10:39 +05:30
Himanshu Chauhan
c3b98c610b include: sbi: Add macro definitions for mseccfg CSR
- Add macros for Machine Security Configuration (mseccfg) CSR
- Add macros to access/manipulate bits in msecfg CSR

Signed-off-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-07-13 12:09:34 +05:30
Anup Patel
72b9c8ff89 lib: sbi: Alphabetically sort HART ISA extensions
Let us follow alphabetical order for HART ISA extension so that
it is simpler to maintain.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Xiang W <wxjstz@126.com>
2023-07-09 11:06:28 +05:30
Anup Patel
669089c5f2 lib: sbi: Add Zihpm as a HART ISA extension
Recently ratified Zihpm ISA extension covers all [m]hpm* CSRs
so we add Zihpm as a HART ISA extension in OpenSBI.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Xiang W <wxjstz@126.com>
2023-07-09 11:06:26 +05:30
Anup Patel
1a398d9faa lib: sbi: Add Zicntr as a HART ISA extension
Recently ratified Zicntr ISA extension covers cycle, time and
instret CSRs so we replace the "time" ISA extension with "zicntr"
ISA extension in OpenSBI.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Xiang W <wxjstz@126.com>
2023-07-09 11:06:24 +05:30
Anup Patel
2552799a1d include: Bump-up version to 1.3
This patch updates OpenSBI version to 1.3 as part of
release preparation.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
2023-06-23 11:01:49 +05:30
Alexandre Ghiti
8153b2622b platform/lib: Set no-map attribute on all PMP regions
This reverts commit 6966ad0abe ("platform/lib: Allow the OS to map the
regions that are protected by PMP").

It was thought at the time of this commit that allowing the kernel to map
PMP protected regions was safe but it is actually not: for example, the
hibernation process will try to access any linear mapping page and then
will fault on such mapped PMP regions [1]. Another issue is that the
device tree specification [2] states that a !no-map region must be
declared as EfiBootServicesData/Code in the EFI memory map which would make
the PMP protected regions reclaimable by the kernel. And to circumvent
this, RISC-V edk2 diverges from the DT specification to declare those
regions as EfiReserved.

The no-map attribute was removed to allow the kernel to use hugepages
larger than 2MB to map the linear mapping to improve the performance but
actually a recent talk from Mike Rapoport [3] stated that the
performance benefit was marginal.

For all those reasons, let's mark all the PMP protected regions as "no-map".

[1] https://lore.kernel.org/linux-riscv/CAAYs2=gQvkhTeioMmqRDVGjdtNF_vhB+vm_1dHJxPNi75YDQ_Q@mail.gmail.com/
[2] "3.5.4 /reserved-memory and UEFI" https://github.com/devicetree-org/devicetree-specification/releases/download/v0.4-rc1/devicetree-specification-v0.4-rc1.pdf
[3] https://lwn.net/Articles/931406/

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Xiang W <wxjstz@126.com>
2023-06-15 18:27:17 +05:30
Anup Patel
66daafe3ba lib: sbi: Use scratch space to save per-HART domain pointer
Instead of using a global array indexed by hartid, we should use
scratch space to save per-HART domain pointer.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-06-05 15:55:21 +05:30
Anup Patel
2a04f70373 lib: sbi: Print scratch size and usage at boot time
The scratch space being a scarce resource so let us print it's
size and usage at boot time.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-06-05 15:46:22 +05:30
Anup Patel
40d36a6673 lib: sbi: Introduce simple heap allocator
We provide simple heap allocator to manage the heap space provided
by OpenSBI firmware and platform.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-06-05 15:46:09 +05:30
Anup Patel
5cf9a54016 platform: Allow platforms to specify heap size
We extend struct sbi_platform and struct sbi_scratch to allow platforms
specify the heap size to the OpenSBI firmwares. The OpenSBI firmwares
will use this information to determine the location of heap and provide
heap base address in per-HART scratch space.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-06-05 15:45:33 +05:30
Anup Patel
aad7a37705 include: sbi_scratch: Add helper macros to access data type
Reading and writing a data type in scratch space is a very common
use-case so let us add related helper macros in sbi_scratch.h.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
2023-06-05 15:42:50 +05:30
Andrew Jones
bdde2ecd27 lib: sbi: Align system suspend errors with spec
The spec says sbi_system_suspend() will return SBI_ERR_INVALID_PARAM
when "sleep_type is reserved or is platform-specific and unimplemented"
and SBI_ERR_NOT_SUPPORTED when sleep_type "is not reserved and is
implemented, but the platform does not support it due to one or more
missing dependencies." Ensure SBI_ERR_INVALID_PARAM is returned for
reserved sleep types and that the system suspend driver can choose
which of the two error types to return itself by returning an error
from its check function rather than a boolean.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-06-04 15:18:40 +05:30
Andrew Jones
33f1722f2b lib: sbi: Document sbi_ecall_extension members
With the introduction of the register_extensions callback the
range members (extid_start and extid_end) may now change and it
has become a bit subtle as to when a probe function should be
implemented. Document all the members and their relationship to
the register_extensions callback.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-05-21 16:54:02 +05:30
Andrew Jones
f58c14090f lib: sbi: Introduce register_extensions extension callback
Rather than registering all extensions on their behalf in
sbi_ecall_init(), introduce another extension callback and
invoke that instead. For now, implement each callback by
simply registering the extension, which means this patch
has no intended functional change. In later patches, extension
callbacks will be modified to choose when to register and to
possibly narrow the extension ID range prior to registering.
When an extension range needs to remove IDs, leaving gaps, then
multiple invocations of sbi_ecall_register_extension() may be
used. In summary, later patches for current extensions and the
introductions of future extensions will use the new callback to
ensure that only valid extension IDs from the initial range,
which are also available, will be registered.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-05-21 16:27:38 +05:30
Xiang W
dc1c7db05e lib: sbi: Simplify BITS_PER_LONG definition
No need to use #elif ladder when defining BITS_PER_LONG.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-05-11 12:56:56 +05:30
Xiang W
4e3353057a lib: sbi: Remove unnecessary semicolon
We have redundant semicolon at quite a few places so let's remove it.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-05-11 12:31:34 +05:30
Xiang W
bf40e07f6f lib: sbi: Optimize sbi_tlb queue waiting
When tlb_fifo is full, it will wait and affect the ipi update to
other harts. This patch is optimized.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
Tested-by: Anup Patel <anup@brainfault.org>
2023-04-14 13:45:30 +05:30
Yu Chien Peter Lin
edc9914392 lib: sbi_pmu: Align the event type offset as per SBI specification
The bits encoded in event_idx[19:16] indicate the event type, with
an offset of 16 instead of 20.

Fixes: 13d40f21d5 ("lib: sbi: Add PMU support")
Signed-off-by: Yu Chien Peter Lin <peterlin@andestech.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Xiang W <wxjstz@126.com>
2023-04-07 10:06:59 +05:30
Sunil V L
33caae8069 lib: sbi: Implement SBI CPPC extension
Implement SBI CPPC extension. This extension is only available when
OpenSBI platform provides a CPPC device to generic library.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-04-07 09:36:01 +05:30
Sunil V L
45ba2b203c include: Add defines for SBI CPPC extension
Add SBI CPPC extension related defines to the
SBI ecall interface header.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-04-07 09:35:06 +05:30
Anup Patel
f64dfcd2b5 lib: sbi: Introduce sbi_entry_count() function
We introduce sbi_entry_count() function which counts the number
of times a HART enters OpenSBI via cold-boot or warm-boot path.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
2023-04-06 18:48:15 +05:30
Xiang W
73ab11dfb0 lib: sbi: Fix how to check whether the domain contains fw_region
Because firmware is split into rw/rx segments, it cannot be recorded
by a root_fw_region. This problem is solved by adding a flag
fw_region_inited to sbi_domain.

Signed-off-by: Xiang W <wxjstz@126.com>
Reviewed-by: Himanshu Chauhan <hchauhan@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-04-06 16:14:35 +05:30
Evgenii Shatokhin
c6a092cd80 lib: sbi: Clear IPIs before init_warm_startup in non-boot harts
Since commit 50d4fde1c5 ("lib: Remove redundant sbi_platform_ipi_clear()
calls"), the IPI sent from the boot hart in wake_coldboot_harts() is not
cleared in the secondary harts until they reach sbi_ipi_init(). However,
sbi_hsm_init() and sbi_hsm_hart_wait() are called earlier, so a secondary
hart might enter sbi_hsm_hart_wait() with an already pending IPI.

sbi_hsm_hart_wait() makes sure the hart leaves the loop only when it is
actually ready, so a pending unrelated IPI should not cause safety issues.
However, it might be inefficient on certain hardware, because it prevents
"wfi" from stalling the hart even if the hardware supports this, making the
hart needlessly spin in a "busy-wait" loop.

This behaviour can be observed, for example, in a QEMU VM (QEMU 7.2.0) with
"-machine virt" running a Linux guest. Inserting delays in
sbi_hsm_hart_start() allows reproducing the issue more reliably.

The comment in wait_for_coldboot() suggests that the initial IPI is needed
in the warm resume path, so let us clear it before init_warm_startup()
only.

To do this, sbi_ipi_raw_clear() was created similar to sbi_ipi_raw_send().

Signed-off-by: Evgenii Shatokhin <e.shatokhin@yadro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:13:40 +05:30
Evgenii Shatokhin
d56049e299 lib: sbi: Refactor the calls to sbi_hart_switch_mode()
Move them into sbi_hsm_hart_start_finish() and sbi_hsm_hart_resume_finish()
to make them easier to manage.

This will be used by subsequent patches.

Suggested-by: Anup Patel <anup@brainfault.org>
Signed-off-by: Evgenii Shatokhin <e.shatokhin@yadro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:00:36 +05:30
Mayuresh Chitale
c631a7da27 lib: sbi_pmu: Add hartid parameter PMU device ops
Platform specific firmware event handler may leverage the hartid to program
per hart specific registers for a given counter.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:00:33 +05:30
Mayuresh Chitale
57d3aa3b0d lib: sbi_pmu: Introduce fw_counter_write_value API
Add fw_counter_write_value API for platform specific firmware events
which separates setting the counter's initial value from starting the
counter. This is required so that the fw_event_data array can be reused
to save the event data received.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:00:30 +05:30
Mayuresh Chitale
b51ddffcc0 lib: sbi_pmu: Update sbi_pmu dev ops
Update fw_event_validate_code, fw_counter_match_code and fw_counter_start
ops which used a 32 bit event code to use the 64 bit event data instead.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:00:26 +05:30
Mayuresh Chitale
60c358e677 lib: sbi_pmu: Reserve space for implementation specific firmware events
We reserve space for SBI implementation specific custom firmware
events which can be used by M-mode firmwares and HS-mode hypervisors
for their own use. This reserved space is intentionally large to
ensure that SBI implementation has enough space to accommodate
platform specific firmware events as well.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:00:22 +05:30
Mayuresh Chitale
51951d9e9a lib: sbi_pmu: Implement sbi_pmu_counter_fw_read_hi
To support 64 bit firmware counters on RV32 systems, we implement
sbi_pmu_counter_fw_read_hi() which returns the upper 32 bits of
the firmware counter value. On RV64 (or higher) systems, this
function will always return zero.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 14:00:07 +05:30
Mayuresh Chitale
1fe8dc9955 lib: sbi_pmu: add callback for counter width
This patch adds a callback to fetch the number of bits implemented for a
custom firmware counter. If the callback fails or is not implemented then
width defaults to 63.

Signed-off-by: Mayuresh Chitale <mchitale@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-10 13:46:52 +05:30
Minda Chen
e9d08bd99c lib: utils/i2c: Add minimal StarFive jh7110 I2C driver
Starfive JH7110 I2C IP is synopsys designware.
Minimum StarFIve I2C driver to read/send bytes over I2C bus.

This allows querying information and perform operation of onboard PMIC,
as well as power-off and reset.

Signed-off-by: Minda Chen <minda.chen@starfivetech.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-03-09 21:00:57 +05:30
Andrew Jones
5ccebf0a7e platform: generic: Add system suspend test
When the system-suspend-test property is present in the domain config
node as shown below, implement system suspend with a simple 5 second
delay followed by a WFI. This allows testing system suspend when the
low-level firmware doesn't support it.

  / {
    chosen {
      opensbi-domains {
          compatible = "opensbi,domain,config";
          system-suspend-test;
      };

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-02-27 19:50:51 +05:30
Andrew Jones
c9917b6108 lib: sbi: Add system_suspend_allowed domain property
Only privileged domains should be allowed to suspend the entire
system. Give the root domain this property by default and allow
other domains to be given the property by specifying it in the
DT.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-02-27 19:45:28 +05:30
Andrew Jones
73623a0aca lib: sbi: Add system suspend skeleton
Add the SUSP extension probe and ecall support, but for now the
system suspend function is just a stub.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-02-27 19:43:52 +05:30
Andrew Jones
8a40306371 lib: sbi_hsm: Export some functions
A coming patch can make use of a few internal hsm functions if
we export them.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-02-27 19:40:21 +05:30
Anup Patel
31b82e0d50 include: sbi: Remove extid parameter from vendor_ext_provider() callback
The extid parameter of vendor_ext_provider() is redundant so let us
remove it.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
2023-02-27 11:26:37 +05:30
Anup Patel
81adc62f45 lib: sbi: Align SBI vendor extension id with mvendorid CSR
As-per the SBI specification, the lower 24bits of the SBI vendor
extension id is same as lower 24bits of the mvendorid CSR.

We update the SBI vendor extension id checking based on above.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
2023-02-27 11:26:35 +05:30
Nylon Chen
30ea8069f4 lib: sbi_hart: Enable hcontext and scontext
According to the description in "riscv-state-enable[0]", to access
h/scontext in S-Mode, we need to enable the 57th bit.

If it is not enabled, an "illegal instruction" error will occur.

Link: a28bfae443/content.adoc [0]

Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
Reviewed-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-02-27 11:22:11 +05:30
Bin Meng
99d09b601e include: fdt/fdt_helper: Change fdt_get_address() to return root.next_arg1
In sbi_domain_finalize(), when locating the coldboot hart's domain,
the coldboot hart's scratch->arg1 will be overwritten by the domain
configuration. However scratch->arg1 holds the FDT address of the
coldboot hart, and is still being accessed by fdt_get_address() in
later boot process. scratch->arg1 could then contain completely
garbage and lead to a crash.

To fix this, we change fdt_get_address() to return root domain's
next_arg1 as the FDT pointer.

Resolves: https://github.com/riscv-software-src/opensbi/issues/281
Fixes: b1678af210 ("lib: sbi: Add initial domain support")
Reported-by: Marouene Boubakri <marouene.boubakri@nxp.com>
Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Anup Patel <anup@brainfault.org>
2023-02-27 10:04:03 +05:30
Anup Patel
c43903c4ea lib: sbi: Add console_puts() callback in the console device
We add console_puts() callback in the console device which allows
console drivers (such as semihosting) to implement a specialized
way to output character string.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-02-10 10:04:41 +05:30
Anup Patel
eab48c33a1 lib: sbi: Add sbi_domain_check_addr_range() function
We add sbi_domain_check_addr_range() helper function to check
whether a given address range is accessible under a particular
domain.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Xiang W <wxjstz@126.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-02-10 09:14:58 +05:30
Anup Patel
4e0572f57b lib: sbi: Add sbi_ngets() function
We add new sbi_ngets() which help us read characters into a
physical memory location.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
2023-02-09 22:30:06 +05:30
Anup Patel
0ee3a86fed lib: sbi: Add sbi_nputs() function
We add new sbi_nputs() which help us print a fixed number of characters
from a physical memory location.

Signed-off-by: Anup Patel <apatel@ventanamicro.com>
Reviewed-by: Atish Patra <atishp@rivosinc.com>
Reviewed-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Xiang W <wxjstz@126.com>
2023-02-09 22:29:24 +05:30