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

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Date: Fri, 21 Jun 2024 17:24:53 -0400
From: Jesse Taube <jesse@...osinc.com>
To: Yunhui Cui <cuiyunhui@...edance.com>
Cc: Palmer Dabbelt <palmer@...osinc.com>, Yunhui Cui
 <cuiyunhui@...edance.com>, corbet@....net, paul.walmsley@...ive.com,
 palmer@...belt.com, aou@...s.berkeley.edu, cleger@...osinc.com,
 evan@...osinc.com, conor.dooley@...rochip.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
Subject: Re: [PATCH v2] RISC-V: Provide the frequency of time CSR via hwprobe



On 6/21/24 07:31, Yunhui Cui wrote:
> 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

Please rebase onto palmers branch as MAX_KEY is already 7.

https://git.kernel.org/pub/scm/linux/kernel/git/palmer/linux.git/log/?h=for-next

Thanks,
Jesse Taube

>   
>   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