linux-kernel - [PATCH v2] RISC-V: Provide the frequency of time CSR via hwprobe

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Message-Id: <20240621113143.35827-1-cuiyunhui@bytedance.com>
Date: Fri, 21 Jun 2024 19:31:43 +0800
From: Yunhui Cui <cuiyunhui@...edance.com>
To: corbet@....net,
	paul.walmsley@...ive.com,
	palmer@...belt.com,
	aou@...s.berkeley.edu,
	cleger@...osinc.com,
	evan@...osinc.com,
	conor.dooley@...rochip.com,
	cuiyunhui@...edance.com,
	costa.shul@...hat.com,
	andy.chiu@...ive.com,
	samitolvanen@...gle.com,
	linux-doc@...r.kernel.org,
	linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc: Palmer Dabbelt <palmer@...osinc.com>
Subject: [PATCH v2] RISC-V: Provide the frequency of time CSR via hwprobe

From: Palmer Dabbelt <palmer@...osinc.com>

A handful of user-visible behavior is based on the frequency of the
time CSR.

Signed-off-by: Palmer Dabbelt <palmer@...osinc.com>
Signed-off-by: Yunhui Cui <cuiyunhui@...edance.com>
---
 Documentation/arch/riscv/hwprobe.rst  | 2 ++
 arch/riscv/include/asm/hwprobe.h      | 2 +-
 arch/riscv/include/uapi/asm/hwprobe.h | 1 +
 arch/riscv/kernel/sys_hwprobe.c       | 5 +++++
 4 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/riscv/hwprobe.rst b/Documentation/arch/riscv/hwprobe.rst
index fc015b452ebf..c07f159d8906 100644
--- a/Documentation/arch/riscv/hwprobe.rst
+++ b/Documentation/arch/riscv/hwprobe.rst
@@ -229,3 +229,5 @@ The following keys are defined:
 
 * :c:macro:`RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE`: An unsigned int which
   represents the size of the Zicboz block in bytes.
+
+* :c:macro:`RISCV_HWPROBE_KEY_TIME_CSR_FREQ`: Frequency (in Hz) of `mtime`.
diff --git a/arch/riscv/include/asm/hwprobe.h b/arch/riscv/include/asm/hwprobe.h
index 630507dff5ea..150a9877b0af 100644
--- a/arch/riscv/include/asm/hwprobe.h
+++ b/arch/riscv/include/asm/hwprobe.h
@@ -8,7 +8,7 @@
 
 #include <uapi/asm/hwprobe.h>
 
-#define RISCV_HWPROBE_MAX_KEY 6
+#define RISCV_HWPROBE_MAX_KEY 7
 
 static inline bool riscv_hwprobe_key_is_valid(__s64 key)
 {
diff --git a/arch/riscv/include/uapi/asm/hwprobe.h b/arch/riscv/include/uapi/asm/hwprobe.h
index 7b95fadbea2a..18754341ff14 100644
--- a/arch/riscv/include/uapi/asm/hwprobe.h
+++ b/arch/riscv/include/uapi/asm/hwprobe.h
@@ -73,6 +73,7 @@ struct riscv_hwprobe {
 #define		RISCV_HWPROBE_MISALIGNED_UNSUPPORTED	(4 << 0)
 #define		RISCV_HWPROBE_MISALIGNED_MASK		(7 << 0)
 #define RISCV_HWPROBE_KEY_ZICBOZ_BLOCK_SIZE	6
+#define RISCV_HWPROBE_KEY_TIME_CSR_FREQ	7
 /* Increase RISCV_HWPROBE_MAX_KEY when adding items. */
 
 /* Flags */
diff --git a/arch/riscv/kernel/sys_hwprobe.c b/arch/riscv/kernel/sys_hwprobe.c
index 83fcc939df67..fc3b40fb9def 100644
--- a/arch/riscv/kernel/sys_hwprobe.c
+++ b/arch/riscv/kernel/sys_hwprobe.c
@@ -8,6 +8,7 @@
 #include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
 #include <asm/hwprobe.h>
+#include <asm/delay.h>
 #include <asm/sbi.h>
 #include <asm/switch_to.h>
 #include <asm/uaccess.h>
@@ -226,6 +227,10 @@ static void hwprobe_one_pair(struct riscv_hwprobe *pair,
 			pair->value = riscv_cboz_block_size;
 		break;
 
+	case RISCV_HWPROBE_KEY_TIME_CSR_FREQ:
+		pair->value = riscv_timebase;
+		break;
+
 	/*
 	 * For forward compatibility, unknown keys don't fail the whole
 	 * call, but get their element key set to -1 and value set to 0
-- 
2.20.1