linux-kernel - [PATCH] drm/panel-simple: Power the panel when probing DP AUX backlight

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Message-Id: <20210714093334.1.Idb41f87e5abae4aee0705db7458b0097fc50e7ab@changeid>
Date:   Wed, 14 Jul 2021 09:33:50 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     Rajeev Nandan <rajeevny@...eaurora.org>,
        Lyude Paul <lyude@...hat.com>,
        Robert Foss <robert.foss@...aro.org>
Cc:     Douglas Anderson <dianders@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Sam Ravnborg <sam@...nborg.org>,
        Thierry Reding <thierry.reding@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH] drm/panel-simple: Power the panel when probing DP AUX backlight

When I tried booting up a device that needed the DP AUX backlight, I
found an error in the logs:
  panel-simple-dp-aux: probe of aux-ti_sn65dsi86.aux.0 failed with error -110

The aux transfers were failing because the panel wasn't powered. Just
like when reading the EDID we need to power the panel when trying to
talk to it. Add the needed pm_runtime calls.

After I do this I can successfully probe the panel and adjust the
backlight on my board.

Fixes: bfd451403d70 ("drm/panel-simple: Support DP AUX backlight")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---

 drivers/gpu/drm/panel/panel-simple.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index e0a05f366ce6..9b286bd4444f 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -827,7 +827,10 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc,
 		goto disable_pm_runtime;
 
 	if (!panel->base.backlight && panel->aux) {
+		pm_runtime_get_sync(dev);
 		err = drm_panel_dp_aux_backlight(&panel->base, panel->aux);
+		pm_runtime_mark_last_busy(dev);
+		pm_runtime_put_autosuspend(dev);
 		if (err)
 			goto disable_pm_runtime;
 	}
-- 
2.32.0.93.g670b81a890-goog