[PATCH RFC 06/11] riscv: suspend: add Smstateen CSRs save/restore

[Max Hsu]

>From Smstateen extension: the values of the [h/s]stateen CSRs will
be lost when entering a non-retentive idle state.
Therefore, these CSRs values need to be restored to ensure that
the corresponding functionality remains enabled.

Signed-off-by: Max Hsu <max.hsu at sifive.com>
---
 arch/riscv/include/asm/suspend.h |  6 ++++++
 arch/riscv/kernel/suspend.c      | 18 ++++++++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/arch/riscv/include/asm/suspend.h b/arch/riscv/include/asm/suspend.h
index 4718096fa5e3..2ecace073869 100644
--- a/arch/riscv/include/asm/suspend.h
+++ b/arch/riscv/include/asm/suspend.h
@@ -17,6 +17,12 @@ struct suspend_context {
 	unsigned long envcfg;
 	unsigned long tvec;
 	unsigned long ie;
+#if __riscv_xlen < 64
+	unsigned long hstateen0h;
+#endif
+	unsigned long hstateen0;
+	unsigned long sstateen0;
+
 #ifdef CONFIG_MMU
 	unsigned long satp;
 #endif
diff --git a/arch/riscv/kernel/suspend.c b/arch/riscv/kernel/suspend.c
index 8a327b485b90..a086da222872 100644
--- a/arch/riscv/kernel/suspend.c
+++ b/arch/riscv/kernel/suspend.c
@@ -19,6 +19,15 @@ void suspend_save_csrs(struct suspend_context *context)
 		context->envcfg = csr_read(CSR_ENVCFG);
 	context->tvec = csr_read(CSR_TVEC);
 	context->ie = csr_read(CSR_IE);
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN)) {
+		if (riscv_has_extension_unlikely(RISCV_ISA_EXT_h)) {
+#if __riscv_xlen < 64
+			context->hstateen0h = csr_read(CSR_HSTATEEN0H);
+#endif
+			context->hstateen0 = csr_read(CSR_HSTATEEN0);
+		}
+		context->sstateen0 = csr_read(CSR_SSTATEEN0);
+	}
 
 	/*
 	 * No need to save/restore IP CSR (i.e. MIP or SIP) because:
@@ -42,6 +51,15 @@ void suspend_restore_csrs(struct suspend_context *context)
 		csr_write(CSR_ENVCFG, context->envcfg);
 	csr_write(CSR_TVEC, context->tvec);
 	csr_write(CSR_IE, context->ie);
+	if (riscv_has_extension_unlikely(RISCV_ISA_EXT_SMSTATEEN)) {
+		if (riscv_has_extension_unlikely(RISCV_ISA_EXT_h)) {
+#if __riscv_xlen < 64
+			csr_write(CSR_HSTATEEN0H, context->hstateen0h);
+#endif
+			csr_write(CSR_HSTATEEN0, context->hstateen0);
+		}
+		csr_write(CSR_SSTATEEN0, context->sstateen0);
+	}
 
 #ifdef CONFIG_MMU
 	csr_write(CSR_SATP, context->satp);

-- 
2.43.2