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In-Reply-To: <20210429133941.531730-1-kai.heng.feng@canonical.com>
From:   Alex Deucher <alexdeucher@gmail.com>
Date:   Thu, 29 Apr 2021 16:06:35 -0400
Message-ID: <CADnq5_MGhFTUOafo_Prjxgek7ufP-9uo59a+_R0=DKZBQayX0Q@mail.gmail.com>
Subject: Re: [PATCH] drm/radeon/dpm: Disable sclk switching when two 4K 60Hz
 monitors are connected
To:     Kai-Heng Feng <kai.heng.feng@canonical.com>
Cc:     "Deucher, Alexander" <alexander.deucher@amd.com>,
        Christian Koenig <christian.koenig@amd.com>,
        David Airlie <airlied@linux.ie>,
        open list <linux-kernel@vger.kernel.org>,
        "open list:DRM DRIVERS" <dri-devel@lists.freedesktop.org>,
        "open list:RADEON and AMDGPU DRM DRIVERS" 
        <amd-gfx@lists.freedesktop.org>
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On Thu, Apr 29, 2021 at 9:40 AM Kai-Heng Feng
<kai.heng.feng@canonical.com> wrote:
>
> Screen flickers rapidly when two 4K 60Hz monitors are connected to an
> Oland card. This issue doesn't happen when one monitor is 4K 60Hz
> (pixelclock 594MHz) and another one is 4K 30Hz (pixelclock 297MHz).
>
> The issue is gone after setting "power_dpm_force_performance_level" to
> "high". Following the lead, we found that the issue only occurs when
> sclk is too low.
>
> So resolve the issue by disabling sclk switching when there are two
> monitors that requires high pixelclock (> 297MHz).
>
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
> ---
>  drivers/gpu/drm/radeon/radeon.h    | 1 +
>  drivers/gpu/drm/radeon/radeon_pm.c | 8 ++++++++
>  drivers/gpu/drm/radeon/si_dpm.c    | 3 +++
>  3 files changed, 12 insertions(+)
>
> diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
> index 42281fce552e6..56ed5634cebef 100644
> --- a/drivers/gpu/drm/radeon/radeon.h
> +++ b/drivers/gpu/drm/radeon/radeon.h
> @@ -1549,6 +1549,7 @@ struct radeon_dpm {
>         void                    *priv;
>         u32                     new_active_crtcs;
>         int                     new_active_crtc_count;
> +       int                     high_pixelclock_count;
>         u32                     current_active_crtcs;
>         int                     current_active_crtc_count;
>         bool single_display;
> diff --git a/drivers/gpu/drm/radeon/radeon_pm.c b/drivers/gpu/drm/radeon/radeon_pm.c
> index 0c1950f4e146f..3861c0b98fcf3 100644
> --- a/drivers/gpu/drm/radeon/radeon_pm.c
> +++ b/drivers/gpu/drm/radeon/radeon_pm.c
> @@ -1767,6 +1767,7 @@ static void radeon_pm_compute_clocks_dpm(struct radeon_device *rdev)
>         struct drm_device *ddev = rdev->ddev;
>         struct drm_crtc *crtc;
>         struct radeon_crtc *radeon_crtc;
> +       struct radeon_connector *radeon_connector;
>
>         if (!rdev->pm.dpm_enabled)
>                 return;
> @@ -1776,6 +1777,7 @@ static void radeon_pm_compute_clocks_dpm(struct radeon_device *rdev)
>         /* update active crtc counts */
>         rdev->pm.dpm.new_active_crtcs = 0;
>         rdev->pm.dpm.new_active_crtc_count = 0;
> +       rdev->pm.dpm.high_pixelclock_count = 0;
>         if (rdev->num_crtc && rdev->mode_info.mode_config_initialized) {
>                 list_for_each_entry(crtc,
>                                     &ddev->mode_config.crtc_list, head) {
> @@ -1783,6 +1785,12 @@ static void radeon_pm_compute_clocks_dpm(struct radeon_device *rdev)
>                         if (crtc->enabled) {
>                                 rdev->pm.dpm.new_active_crtcs |= (1 << radeon_crtc->crtc_id);
>                                 rdev->pm.dpm.new_active_crtc_count++;
> +                               if (!radeon_crtc->connector)
> +                                       continue;
> +
> +                               radeon_connector = to_radeon_connector(radeon_crtc->connector);
> +                               if (radeon_connector->pixelclock_for_modeset > 297000)
> +                                       rdev->pm.dpm.high_pixelclock_count++;
>                         }
>                 }
>         }
> diff --git a/drivers/gpu/drm/radeon/si_dpm.c b/drivers/gpu/drm/radeon/si_dpm.c
> index 9186095518047..be6fa3257d1bc 100644
> --- a/drivers/gpu/drm/radeon/si_dpm.c
> +++ b/drivers/gpu/drm/radeon/si_dpm.c
> @@ -2995,6 +2995,9 @@ static void si_apply_state_adjust_rules(struct radeon_device *rdev,
>             ni_dpm_vblank_too_short(rdev))
>                 disable_mclk_switching = true;
>
> +       if (rdev->pm.dpm.high_pixelclock_count > 1)
> +               disable_sclk_switching = true;
> +

I would suggest limiting this to just Oland.

Alex


>         if (rps->vclk || rps->dclk) {
>                 disable_mclk_switching = true;
>                 disable_sclk_switching = true;
> --
> 2.30.2
>
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