linux-kernel - Re: [PATCH v2] Revert "drm/amd/display: Only restore backlight after amdgpu_dm_init or dm

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Message-ID: <CADnq5_NauQ3YSngQ4mtx=L1t5yuxWZYHLRn-Je8rL3yYhYOqMA@mail.gmail.com>
Date: Thu, 9 Oct 2025 10:57:27 -0400
From: Alex Deucher <alexdeucher@...il.com>
To: Matthew Schwartz <matthew.schwartz@...ux.dev>
Cc: harry.wentland@....com, christian.koenig@....com, sunpeng.li@....com, 
	airlied@...il.com, simona@...ll.ch, alexander.deucher@....com, 
	linux-kernel@...r.kernel.org, mario.limonciello@....com, 
	amd-gfx@...ts.freedesktop.org, regressions@...ts.linux.dev, 
	stable@...r.kernel.org
Subject: Re: [PATCH v2] Revert "drm/amd/display: Only restore backlight after
 amdgpu_dm_init or dm_resume"

Applied.  Thanks.

Alex

On Thu, Oct 9, 2025 at 8:51 AM Matthew Schwartz
<matthew.schwartz@...ux.dev> wrote:
>
> This fix regressed the original issue that commit d83c747a1225
> ("drm/amd/display: Fix brightness level not retained over reboot") solved,
> so revert it until a different approach to solve the regression that
> it caused with AMD_PRIVATE_COLOR is found.
>
> Fixes: a490c8d77d50 ("drm/amd/display: Only restore backlight after amdgpu_dm_init or dm_resume")
> Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4620
> Cc: stable@...r.kernel.org
> Signed-off-by: Matthew Schwartz <matthew.schwartz@...ux.dev>
> ---
> v1 -> v2:
> - Fix missing stable tag
> ---
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 12 ++++--------
>  drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h |  7 -------
>  2 files changed, 4 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> index 8e1622bf7a42..21281e684b84 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
> @@ -2081,8 +2081,6 @@ static int amdgpu_dm_init(struct amdgpu_device *adev)
>
>         dc_hardware_init(adev->dm.dc);
>
> -       adev->dm.restore_backlight = true;
> -
>         adev->dm.hpd_rx_offload_wq = hpd_rx_irq_create_workqueue(adev);
>         if (!adev->dm.hpd_rx_offload_wq) {
>                 drm_err(adev_to_drm(adev), "failed to create hpd rx offload workqueue.\n");
> @@ -3438,7 +3436,6 @@ static int dm_resume(struct amdgpu_ip_block *ip_block)
>                 dc_set_power_state(dm->dc, DC_ACPI_CM_POWER_STATE_D0);
>
>                 dc_resume(dm->dc);
> -               adev->dm.restore_backlight = true;
>
>                 amdgpu_dm_irq_resume_early(adev);
>
> @@ -9965,6 +9962,7 @@ static void amdgpu_dm_commit_streams(struct drm_atomic_state *state,
>         bool mode_set_reset_required = false;
>         u32 i;
>         struct dc_commit_streams_params params = {dc_state->streams, dc_state->stream_count};
> +       bool set_backlight_level = false;
>
>         /* Disable writeback */
>         for_each_old_connector_in_state(state, connector, old_con_state, i) {
> @@ -10084,6 +10082,7 @@ static void amdgpu_dm_commit_streams(struct drm_atomic_state *state,
>                         acrtc->hw_mode = new_crtc_state->mode;
>                         crtc->hwmode = new_crtc_state->mode;
>                         mode_set_reset_required = true;
> +                       set_backlight_level = true;
>                 } else if (modereset_required(new_crtc_state)) {
>                         drm_dbg_atomic(dev,
>                                        "Atomic commit: RESET. crtc id %d:[%p]\n",
> @@ -10140,16 +10139,13 @@ static void amdgpu_dm_commit_streams(struct drm_atomic_state *state,
>          * to fix a flicker issue.
>          * It will cause the dm->actual_brightness is not the current panel brightness
>          * level. (the dm->brightness is the correct panel level)
> -        * So we set the backlight level with dm->brightness value after initial
> -        * set mode. Use restore_backlight flag to avoid setting backlight level
> -        * for every subsequent mode set.
> +        * So we set the backlight level with dm->brightness value after set mode
>          */
> -       if (dm->restore_backlight) {
> +       if (set_backlight_level) {
>                 for (i = 0; i < dm->num_of_edps; i++) {
>                         if (dm->backlight_dev[i])
>                                 amdgpu_dm_backlight_set_level(dm, i, dm->brightness[i]);
>                 }
> -               dm->restore_backlight = false;
>         }
>  }
>
> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> index 009f206226f0..db75e991ac7b 100644
> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.h
> @@ -630,13 +630,6 @@ struct amdgpu_display_manager {
>          */
>         u32 actual_brightness[AMDGPU_DM_MAX_NUM_EDP];
>
> -       /**
> -        * @restore_backlight:
> -        *
> -        * Flag to indicate whether to restore backlight after modeset.
> -        */
> -       bool restore_backlight;
> -
>         /**
>          * @aux_hpd_discon_quirk:
>          *
> --
> 2.51.0
>