linux-kernel - Re: [PATCH v3 3/3] drm/v3d: Make sure the GPU is on when measuring clocks.

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Message-ID: <CAApk1dVxEvinAE+7Vw2_Rb1hyJMXnbxKDGyJmwgTN=a=7seJSg@mail.gmail.com>
Date:   Fri, 8 Mar 2019 16:47:11 +0000
From:   Dave Emett <david.emett@...adcom.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        Thomas Spurden <thomas.spurden@...adcom.com>
Subject: Re: [PATCH v3 3/3] drm/v3d: Make sure the GPU is on when measuring clocks.

On Wed, 20 Feb 2019 at 23:37, Eric Anholt <eric@...olt.net> wrote:
>
> You'll get garbage measurements if the registers always read back
> 0xdeadbeef
>
> Signed-off-by: Eric Anholt <eric@...olt.net>

Reviewed-by: Dave Emett <david.emett@...adcom.com>

> ---
>  drivers/gpu/drm/v3d/v3d_debugfs.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/v3d/v3d_debugfs.c b/drivers/gpu/drm/v3d/v3d_debugfs.c
> index eb2b2d2f8553..a24af2d2f574 100644
> --- a/drivers/gpu/drm/v3d/v3d_debugfs.c
> +++ b/drivers/gpu/drm/v3d/v3d_debugfs.c
> @@ -187,6 +187,11 @@ static int v3d_measure_clock(struct seq_file *m, void *unused)
>         uint32_t cycles;
>         int core = 0;
>         int measure_ms = 1000;
> +       int ret;
> +
> +       ret = pm_runtime_get_sync(v3d->dev);
> +       if (ret < 0)
> +               return ret;
>
>         if (v3d->ver >= 40) {
>                 V3D_CORE_WRITE(core, V3D_V4_PCTR_0_SRC_0_3,
> @@ -210,6 +215,9 @@ static int v3d_measure_clock(struct seq_file *m, void *unused)
>                    cycles / (measure_ms * 1000),
>                    (cycles / (measure_ms * 100)) % 10);
>
> +       pm_runtime_mark_last_busy(v3d->dev);
> +       pm_runtime_put_autosuspend(v3d->dev);
> +
>         return 0;
>  }
>
> --
> 2.20.1
>