On Mon, Mar 25, 2024 at 2:57 PM Douglas Anderson <dianders@xxxxxxxxxxxx> wrote:
>
> If we're using the AUX channel for eDP backlight and it fails to probe
> for some reason, let's _not_ fail the panel probe.
>
> At least one case where we could fail to init the backlight is because
> of a dead or physically missing panel. As talked about in detail in
> the earlier patch in this series, ("drm/panel-edp: If we fail to
> powerup/get EDID, use conservative timings"), this can cause the
> entire system's display pipeline to fail to come up and that's
> non-ideal.
>
> If we fail to init the backlight for some transitory reason, we should
> dig in and see if there's a way to fix this (perhaps retries?). Even
> in that case, though, having a panel whose backlight is stuck at 100%
> (the default, at least in the panel Samsung ATNA33XC20 I tested) is
> better than having no panel at all.
>
> Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
Reviewed-by: Hsin-Yi Wang <hsinyi@xxxxxxxxxxxx>
> ---
> If needed, I could split this into two patches: one for each of the
> two panels that use drm_panel_dp_aux_backlight(). Since they both go
> through drm-misc, though, it doesn't feel worth it.
>
> drivers/gpu/drm/panel/panel-edp.c | 8 +++++++-
> drivers/gpu/drm/panel/panel-samsung-atna33xc20.c | 9 +++++++--
> 2 files changed, 14 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/panel/panel-edp.c b/drivers/gpu/drm/panel/panel-edp.c
> index 607cdd6feda9..0bf66d9dd5b8 100644
> --- a/drivers/gpu/drm/panel/panel-edp.c
> +++ b/drivers/gpu/drm/panel/panel-edp.c
> @@ -944,8 +944,14 @@ static int panel_edp_probe(struct device *dev, const struct panel_desc *desc,
> err = drm_panel_dp_aux_backlight(&panel->base, panel->aux);
> pm_runtime_mark_last_busy(dev);
> pm_runtime_put_autosuspend(dev);
> +
> + /*
> + * Warn if we get an error, but don't consider it fatal. Having
> + * a panel where we can't control the backlight is better than
> + * no panel.
> + */
> if (err)
> - goto err_finished_pm_runtime;
> + dev_warn(dev, "failed to register dp aux backlight: %d\n", err);
> }
>
> drm_panel_add(&panel->base);
> diff --git a/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c b/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c
> index 9c336c71562b..6828a4f24d14 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-atna33xc20.c
> @@ -328,9 +328,14 @@ static int atana33xc20_probe(struct dp_aux_ep_device *aux_ep)
> ret = drm_panel_dp_aux_backlight(&panel->base, aux_ep->aux);
> pm_runtime_mark_last_busy(dev);
> pm_runtime_put_autosuspend(dev);
> +
> + /*
> + * Warn if we get an error, but don't consider it fatal. Having
> + * a panel where we can't control the backlight is better than
> + * no panel.
> + */
> if (ret)
> - return dev_err_probe(dev, ret,
> - "failed to register dp aux backlight\n");
> + dev_warn(dev, "failed to register dp aux backlight: %d\n", ret);
>
> drm_panel_add(&panel->base);
>
> --
> 2.44.0.396.g6e790dbe36-goog
>
