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riscv: Do not save the scratch CSR during suspend

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While the processor is executing kernel code, the value of the scratch
CSR is always zero, so there is no need to save the value. Continue to
write the CSR during the resume flow, so we do not rely on firmware to
initialize it.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Link: https://lore.kernel.org/r/20240312195641.1830521-1-samuel.holland@sifive.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
This commit is contained in:
Samuel Holland 2024-03-12 12:56:38 -07:00 committed by Palmer Dabbelt
parent d4b500cceb
commit fa7d733901
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2 changed files with 1 additions and 3 deletions
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1
arch/riscv/include/asm/suspend.h
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@ -13,7 +13,6 @@ struct suspend_context {
/* Saved and restored by low-level functions */
struct pt_regs regs;
/* Saved and restored by high-level functions */
unsigned long scratch;
unsigned long envcfg;
unsigned long tvec;
unsigned long ie;

3
arch/riscv/kernel/suspend.c
View File

@ -14,7 +14,6 @@
void suspend_save_csrs(struct suspend_context *context)
{
context->scratch = csr_read(CSR_SCRATCH);
if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))
context->envcfg = csr_read(CSR_ENVCFG);
context->tvec = csr_read(CSR_TVEC);
@ -37,7 +36,7 @@ void suspend_save_csrs(struct suspend_context *context)
void suspend_restore_csrs(struct suspend_context *context)
{
csr_write(CSR_SCRATCH, context->scratch);
csr_write(CSR_SCRATCH, 0);
if (riscv_cpu_has_extension_unlikely(smp_processor_id(), RISCV_ISA_EXT_XLINUXENVCFG))
csr_write(CSR_ENVCFG, context->envcfg);
csr_write(CSR_TVEC, context->tvec);