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

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Date: Sat, 22 Jun 2024 10:43:56 +0800
From: yunhui cui <cuiyunhui@...edance.com>
To: Jesse Taube <jesse@...osinc.com>
Cc: Palmer Dabbelt <palmer@...osinc.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: [External] Re: [PATCH v2] RISC-V: Provide the frequency of time
 CSR via hwprobe

Hi Jesse,


On Sat, Jun 22, 2024 at 5:25 AM Jesse Taube <jesse@...osinc.com> wrote:
>
>
>
> 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
Okay, I will update it on v3, thanks.

>
> 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

Thanks,
Yunhui