[PATCH 2/2] riscv: andes: Add Smstateen extension support

[Heinrich Schuchardt]

Am 24. März 2026 20:03:48 MEZ schrieb Heinrich Schuchardt <xypron.glpk at gmx.de>:
>Am 19. März 2026 09:29:11 MEZ schrieb Leo Yu-Chi Liang <ycliang at andestech.com>:
>>Use the CSR detection mechanism to probe for the Smstateen extension
>>and initialize mstateen0/sstateen0 CSRs when present.
>>
>>The mstateen0 register is configured to allow S-mode access to fcsr,
>>AIA, IMSIC, indirect CSR access, environment configuration, and
>>sstateen0. The sstateen0 register enables U-mode access to compressed
>>extension state and fcsr.
>>
>>Supports both RV32 (using MSTATEEN0/MSTATEEN0H split) and RV64.
>
>Why is this change needed in U-Boot?
>Does EDK II do the same?
>Isn't this the kernel's job?

And why add this in Andes code and not in the generic code?

>
>Best regards
>
>Heinrich
>
>>
>>Signed-off-by: Leo Yu-Chi Liang <ycliang at andestech.com>
>>---
>> arch/riscv/cpu/andes/cpu.c   | 29 +++++++++++++++++++++++++++++
>> arch/riscv/include/asm/csr.h | 15 +++++++++++++++
>> 2 files changed, 44 insertions(+)
>>
>>diff --git a/arch/riscv/cpu/andes/cpu.c b/arch/riscv/cpu/andes/cpu.c
>>index d25ecba0e88..feb755a4f0d 100644
>>--- a/arch/riscv/cpu/andes/cpu.c
>>+++ b/arch/riscv/cpu/andes/cpu.c
>>@@ -9,6 +9,7 @@
>> #include <irq_func.h>
>> #include <asm/cache.h>
>> #include <asm/csr.h>
>>+#include <asm/csr_detect.h>
>> #include <asm/arch-andes/csr.h>
>> 
>> /*
>>@@ -60,5 +61,33 @@ void harts_early_init(void)
>> 		mmisc_ctl_val |= MMISC_CTL_NON_BLOCKING_EN;
>> 
>> 		csr_write(CSR_MMISC_CTL, mmisc_ctl_val);
>>+
>>+		/* Initialize Smstateen if the extension is present */
>>+		{
>>+			int trap = 0;
>>+			unsigned long long mstateen0;
>>+
>>+			mstateen0 = csr_read_allowed(CSR_MSTATEEN0, trap);
>>+			if (!trap) {
>>+#if __riscv_xlen == 32
>>+				mstateen0 |= (unsigned long long)
>>+					csr_read(CSR_MSTATEEN0H) << 32;
>>+#endif
>>+				mstateen0 |= SMSTATEEN0_CS | SMSTATEEN0_FCSR |
>>+					     SMSTATEEN0_CONTEXT |
>>+					     SMSTATEEN0_IMSIC |
>>+					     SMSTATEEN0_AIA |
>>+					     SMSTATEEN0_CSRIND |
>>+					     SMSTATEEN0_ENVCFG |
>>+					     SMSTATEEN0_SE0;
>>+				csr_write(CSR_MSTATEEN0, mstateen0);
>>+#if __riscv_xlen == 32
>>+				csr_write(CSR_MSTATEEN0H, mstateen0 >> 32);
>>+#endif
>>+				csr_write(CSR_SSTATEEN0,
>>+					  csr_read(CSR_SSTATEEN0) |
>>+					  SMSTATEEN0_CS | SMSTATEEN0_FCSR);
>>+			}
>>+		}
>> 	}
>> }
>>diff --git a/arch/riscv/include/asm/csr.h b/arch/riscv/include/asm/csr.h
>>index 986f951c31a..cef0fd906da 100644
>>--- a/arch/riscv/include/asm/csr.h
>>+++ b/arch/riscv/include/asm/csr.h
>>@@ -97,6 +97,18 @@
>> #define SIE_STIE		(_AC(0x1, UL) << IRQ_S_TIMER)
>> #define SIE_SEIE		(_AC(0x1, UL) << IRQ_S_EXT)
>> 
>>+/* Smstateen: mstateen0 / sstateen0 bit definitions */
>>+#define SMSTATEEN0_CS		(_AC(0x1, ULL) << 0)
>>+#define SMSTATEEN0_FCSR		(_AC(0x1, ULL) << 1)
>>+#define SMSTATEEN0_JVT		(_AC(0x1, ULL) << 2)
>>+#define SMSTATEEN0_CONTEXT	(_AC(0x1, ULL) << 57)
>>+#define SMSTATEEN0_IMSIC	(_AC(0x1, ULL) << 58)
>>+#define SMSTATEEN0_AIA		(_AC(0x1, ULL) << 59)
>>+#define SMSTATEEN0_CSRIND	(_AC(0x1, ULL) << 60)
>>+#define SMSTATEEN0_P1P13	(_AC(0x1, ULL) << 61)
>>+#define SMSTATEEN0_ENVCFG	(_AC(0x1, ULL) << 62)
>>+#define SMSTATEEN0_SE0		(_AC(0x1, ULL) << 63)
>>+
>> #define CSR_FCSR		0x003
>> #define CSR_CYCLE		0xc00
>> #define CSR_TIME		0xc01
>>@@ -105,6 +117,7 @@
>> #define CSR_SIE			0x104
>> #define CSR_STVEC		0x105
>> #define CSR_SCOUNTEREN		0x106
>>+#define CSR_SSTATEEN0		0x10c
>> #define CSR_SSCRATCH		0x140
>> #define CSR_SEPC		0x141
>> #define CSR_SCAUSE		0x142
>>@@ -126,6 +139,8 @@
>> #else
>> #define CSR_MCOUNTEREN		0x306
>> #endif
>>+#define CSR_MSTATEEN0		0x30c
>>+#define CSR_MSTATEEN0H		0x31c
>> #define CSR_MSCRATCH		0x340
>> #define CSR_MEPC		0x341
>> #define CSR_MCAUSE		0x342
>