[PATCH] riscv: Do not save the scratch CSR during suspend

[Samuel Holland]

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 at sifive.com>
---

 arch/riscv/include/asm/suspend.h | 1 -
 arch/riscv/kernel/suspend.c      | 3 +--
 2 files changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h
index 491296a335d0..6569eefacf38 100644
--- a/arch/riscv/include/asm/suspend.h
+++ b/arch/riscv/include/asm/suspend.h
@@ -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;
diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c
index 299795341e8a..3d306d8a253d 100644
--- a/arch/riscv/kernel/suspend.c
+++ b/arch/riscv/kernel/suspend.c
@@ -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);
-- 
2.43.1