linux-kernel - Re: [PATCH V3 2/6] csky: Add reg-io-width property for csky pmu

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Message-ID: <CAJF2gTR=woyeq9+05qASs4pyjvUj7BHwyGY5Rex1ia7_dmdudA@mail.gmail.com>
Date:   Mon, 3 Jun 2019 16:20:25 +0800
From:   Guo Ren <guoren@...nel.org>
To:     Mao Han <han_mao@...ky.com>
Cc:     linux-kernel@...r.kernel.org, linux-csky@...r.kernel.org
Subject: Re: [PATCH V3 2/6] csky: Add reg-io-width property for csky pmu

Hello Mao,

Title Correct: csky: Add reg-io-width property for csky pmu
It's not a reg-io-width. I think it's a count-width, isn't it?

On Mon, Jun 3, 2019 at 2:47 PM Mao Han <han_mao@...ky.com> wrote:
>
> csky pmu counter may have different io width. When the counter is smaller
Csky pmu counter ..., capitalize the first letter.

> then 64 bits and counter value is smaller than the old value, it will
> result to a extremely large delta value. So the sampled value should be
> extend to 64 bits to avoid this, the extension bits base on the
> reg-io-width property from dts.
>
> Signed-off-by: Mao Han <han_mao@...ky.com>
> CC: Guo Ren <guoren@...nel.org>
Please correct to "Cc:"

> CC: linux-csky@...r.kernel.org
Remove it and don't add mailing list in commit msg, Cc means you want
who to pick up the patch.

> ---
>  arch/csky/kernel/perf_event.c | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
>
> diff --git a/arch/csky/kernel/perf_event.c b/arch/csky/kernel/perf_event.c
> index c022acc..f1b3cdf 100644
> --- a/arch/csky/kernel/perf_event.c
> +++ b/arch/csky/kernel/perf_event.c
> @@ -18,6 +18,7 @@ static void (*hw_raw_write_mapping[CSKY_PMU_MAX_EVENTS])(uint64_t val);
>
>  struct csky_pmu_t {
>         struct pmu      pmu;
> +       uint32_t        sign_extend;
Please use count_width here.

>         uint32_t        hpcr;
>  } csky_pmu;
>
> @@ -806,7 +807,13 @@ static void csky_perf_event_update(struct perf_event *event,
>                                    struct hw_perf_event *hwc)
>  {
>         uint64_t prev_raw_count = local64_read(&hwc->prev_count);
> -       uint64_t new_raw_count = hw_raw_read_mapping[hwc->idx]();
> +       /*
> +        * Extend count value to 64bit, otherwise delta calculation would
Sign extend count value to 64bit, ...

> +        * be incorrect when overflow occurs.
> +        */
> +       uint64_t new_raw_count = ((int64_t)hw_raw_read_mapping[hwc->idx]()
> +                                  << csky_pmu.sign_extend)
> +                                  >> csky_pmu.sign_extend;
Please use sign_extend64 in bitops.h.

+       uint64_t new_raw_count = ((int64_t)hw_raw_read_mapping[hwc->idx]()
+                                  << 64 - csky_pmu.count_width)
+                                  >> 64 - csky_pmu.count_width;

>         int64_t delta = new_raw_count - prev_raw_count;
>
>         /*
> @@ -1037,6 +1044,7 @@ int csky_pmu_device_probe(struct platform_device *pdev,
>         const struct of_device_id *of_id;
>         csky_pmu_init init_fn;
>         struct device_node *node = pdev->dev.of_node;
> +       int cnt_width;
Please remove.

>         int ret = -ENODEV;
>
>         of_id = of_match_node(of_table, pdev->dev.of_node);
> @@ -1045,6 +1053,12 @@ int csky_pmu_device_probe(struct platform_device *pdev,
>                 ret = init_fn(&csky_pmu);
>         }
>
> +       if (!of_property_read_u32(node, "reg-io-width", &cnt_width)) {
> +               csky_pmu.sign_extend = 64 - cnt_width;
63?
Please use count_width, see above.

> +       } else {
> +               csky_pmu.sign_extend = 16;
Please define a macro for define DEFAULT_COUNT_WIDTH 48 and change the
format like this:

       if (of_property_read_u32(node, "count-width", &csky_pmu.count_width))
               csky_pmu.count_width = DEFAULT_COUNT_WIDTH;

Best Regards


 Guo Ren