linux-kernel - Re: [PATCH v2 3/3] drm/i915: Move to new PM core fields

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Message-ID: <CAPDyKFrvrN6+sVGc1sM+hmQo=JR=8FyAz_YRK9DzEQN2jOVX6w@mail.gmail.com>
Date:   Fri, 14 Dec 2018 15:36:07 +0100
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     Vincent Guittot <vincent.guittot@...aro.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Thara Gopinath <thara.gopinath@...aro.org>,
        jani.nikula@...ux.intel.com,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        rodrigo.vivi@...el.com, David Airlie <airlied@...ux.ie>,
        "Intel graphics driver community testing & development" 
        <intel-gfx@...ts.freedesktop.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v2 3/3] drm/i915: Move to new PM core fields

On Fri, 14 Dec 2018 at 15:22, Vincent Guittot
<vincent.guittot@...aro.org> wrote:
>
> With jiffies been replaced by raw ns in PM core accounting, 915 driver is
> updated to use this new time infrastructure.
>
> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
> ---
>  drivers/gpu/drm/i915/i915_pmu.c | 12 ++++++------
>  drivers/gpu/drm/i915/i915_pmu.h |  4 ++--
>  2 files changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> index d6c8f8f..cf6437d 100644
> --- a/drivers/gpu/drm/i915/i915_pmu.c
> +++ b/drivers/gpu/drm/i915/i915_pmu.c
> @@ -493,14 +493,14 @@ static u64 get_rc6(struct drm_i915_private *i915)
>                  */
>                 if (kdev->power.runtime_status == RPM_SUSPENDED) {
>                         if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
> -                               i915->pmu.suspended_jiffies_last =
> -                                                 kdev->power.suspended_jiffies;
> +                               i915->pmu.suspended_time_last =
> +                                       kdev->power.suspended_time;
>

Huh, so patch 2 introduces a complier error because of removing the
old fields. We can't have that.

Ideally the driver shouldn't touch these fields in the first place,
but because the fields are defined in a public header, there is always
a risk that they becomes abused. I would appreciate if we can change
the driver move away from using these fields and make that a patch
preceding patch 2.

> -                       val = kdev->power.suspended_jiffies -
> -                             i915->pmu.suspended_jiffies_last;
> -                       val += jiffies - kdev->power.accounting_timestamp;
> +                       val = kdev->power.suspended_time -
> +                               i915->pmu.suspended_time_last;
> +                       val += ktime_to_ns(ktime_get()) -
> +                               kdev->power.accounting_timestamp;
>
> -                       val = jiffies_to_nsecs(val);
>                         val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
>
>                         i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
> diff --git a/drivers/gpu/drm/i915/i915_pmu.h b/drivers/gpu/drm/i915/i915_pmu.h
> index 7f164ca..3dc2a30 100644
> --- a/drivers/gpu/drm/i915/i915_pmu.h
> +++ b/drivers/gpu/drm/i915/i915_pmu.h
> @@ -95,9 +95,9 @@ struct i915_pmu {
>          */
>         struct i915_pmu_sample sample[__I915_NUM_PMU_SAMPLERS];
>         /**
> -        * @suspended_jiffies_last: Cached suspend time from PM core.
> +        * @suspended_time_last: Cached suspend time from PM core.
>          */
> -       unsigned long suspended_jiffies_last;
> +       u64 suspended_time_last;
>         /**
>          * @i915_attr: Memory block holding device attributes.
>          */
> --
> 2.7.4
>

Kind regards
Uffe