linux-kernel - Re: [PATCH v2] loongarch: time: Derive max

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Message-ID: <CAAhV-H7qvq9_D=nYrRUVWH_PAHYo8Z5OzVEAiT8Q12hyy2rZ6A@mail.gmail.com>
Date: Sat, 4 Jan 2025 21:36:31 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Jiaxun Yang <jiaxun.yang@...goat.com>
Cc: WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] loongarch: time: Derive max_delta from prcfg1 tmrbits

Applied, thanks.

Huacai

On Fri, Jan 3, 2025 at 8:10 PM Jiaxun Yang <jiaxun.yang@...goat.com> wrote:
>
> As per arch spec, maximum timer bits is configurable and
> should not be hardcoded in any way.
>
> Probe timer bits from prcfg1 and use that to determine
> clockevent's max_delta to be conformance.
>
> Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
> ---
> Changes in v2:
> - Move probing to cpu-probe
> - Link to v1: https://lore.kernel.org/r/20250102-la-misc-v1-1-8dc7db525e54@flygoat.com
> ---
>  arch/loongarch/include/asm/cpu-info.h  | 1 +
>  arch/loongarch/include/asm/loongarch.h | 1 -
>  arch/loongarch/kernel/cpu-probe.c      | 2 ++
>  arch/loongarch/kernel/time.c           | 2 +-
>  4 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/loongarch/include/asm/cpu-info.h b/arch/loongarch/include/asm/cpu-info.h
> index 900589cb159de4e5997358443c5b5e3e50f92239..fb28ba9e3011c9256da4a9748de97236ae7f001f 100644
> --- a/arch/loongarch/include/asm/cpu-info.h
> +++ b/arch/loongarch/include/asm/cpu-info.h
> @@ -57,6 +57,7 @@ struct cpuinfo_loongarch {
>         int                     global_id; /* physical global thread number */
>         int                     vabits; /* Virtual Address size in bits */
>         int                     pabits; /* Physical Address size in bits */
> +       int                     timerbits; /* Width of timer in bits */
>         unsigned int            ksave_mask; /* Usable KSave mask. */
>         unsigned int            watch_dreg_count;   /* Number data breakpoints */
>         unsigned int            watch_ireg_count;   /* Number instruction breakpoints */
> diff --git a/arch/loongarch/include/asm/loongarch.h b/arch/loongarch/include/asm/loongarch.h
> index 64ad277e096edd7d77af6f37e234d68e571764a4..a3cc4f8d4c4a0b0521ef2b76c87fa57eca417d75 100644
> --- a/arch/loongarch/include/asm/loongarch.h
> +++ b/arch/loongarch/include/asm/loongarch.h
> @@ -466,7 +466,6 @@
>
>  #define LOONGARCH_CSR_TCFG             0x41    /* Timer config */
>  #define  CSR_TCFG_VAL_SHIFT            2
> -#define         CSR_TCFG_VAL_WIDTH             48
>  #define  CSR_TCFG_VAL                  (_ULCAST_(0x3fffffffffff) << CSR_TCFG_VAL_SHIFT)
>  #define  CSR_TCFG_PERIOD_SHIFT         1
>  #define  CSR_TCFG_PERIOD               (_ULCAST_(0x1) << CSR_TCFG_PERIOD_SHIFT)
> diff --git a/arch/loongarch/kernel/cpu-probe.c b/arch/loongarch/kernel/cpu-probe.c
> index cbce099037b2728b82ecb9c5aa58e05b07695c5a..06c98ddf29490571e8b927b4ca721c27ff7f0ea8 100644
> --- a/arch/loongarch/kernel/cpu-probe.c
> +++ b/arch/loongarch/kernel/cpu-probe.c
> @@ -192,6 +192,8 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
>         config = read_csr_prcfg1();
>         c->ksave_mask = GENMASK((config & CSR_CONF1_KSNUM) - 1, 0);
>         c->ksave_mask &= ~(EXC_KSAVE_MASK | PERCPU_KSAVE_MASK | KVM_KSAVE_MASK);
> +       c->timerbits = (config & CSR_CONF1_TMRBITS) >> CSR_CONF1_TMRBITS_SHIFT;
> +       c->timerbits += 1;
>
>         config = read_csr_prcfg3();
>         switch (config & CSR_CONF3_TLBTYPE) {
> diff --git a/arch/loongarch/kernel/time.c b/arch/loongarch/kernel/time.c
> index a07d7eff4dc5fb0f41f5fad02698ff7a84c7bc8a..ebfdab6b155585dbab08b7cc49cba627a59854ec 100644
> --- a/arch/loongarch/kernel/time.c
> +++ b/arch/loongarch/kernel/time.c
> @@ -132,7 +132,7 @@ int constant_clockevent_init(void)
>  #else
>         unsigned long min_delta = 1000;
>  #endif
> -       unsigned long max_delta = (1UL << 48) - 1;
> +       unsigned long max_delta = CLOCKSOURCE_MASK(current_cpu_data.timerbits);
>         struct clock_event_device *cd;
>         static int irq = 0, timer_irq_installed = 0;
>
>
> ---
> base-commit: 8155b4ef3466f0e289e8fcc9e6e62f3f4dceeac2
> change-id: 20241223-la-misc-d610d14f947e
>
> Best regards,
> --
> Jiaxun Yang <jiaxun.yang@...goat.com>
>