linux-kernel - [PATCH v2 1/5] drm/panel-simple: Undo enable if HPD never asserts

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Message-Id: <20210115144345.v2.1.I33fcbd64ab409cfe4f9491bf449f51925a4d3281@changeid>
Date:   Fri, 15 Jan 2021 14:44:16 -0800
From:   Douglas Anderson <dianders@...omium.org>
To:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>
Cc:     Rob Clark <robdclark@...omium.org>,
        Stephen Boyd <swboyd@...omium.org>,
        Douglas Anderson <dianders@...omium.org>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Linus Walleij <linus.walleij@...aro.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/5] drm/panel-simple: Undo enable if HPD never asserts

If the HPD signal never asserts in panel_simple_prepare() and we
return an error, we should unset the enable GPIO and disable the
regulator to make it consistent for the caller.

At the moment I have some hardware where HPD sometimes doesn't assert.
Obviously that needs to be debugged, but this patch makes it so that
if I add a retry that I can make things work.

Fixes: 48834e6084f1 ("drm/panel-simple: Support hpd-gpios for delaying prepare()")
Signed-off-by: Douglas Anderson <dianders@...omium.org>
---
Stephen: I didn't take your Reviewed-by tag since I made a small
change.  If you're OK with this change please re-add.

Changes in v2:
- Set the "unprepared_time" so if we retry we give the proper delay.

 drivers/gpu/drm/panel/panel-simple.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 71ae200ac48a..581ab6810b70 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -406,7 +406,7 @@ static int panel_simple_prepare(struct drm_panel *panel)
 		if (IS_ERR(p->hpd_gpio)) {
 			err = panel_simple_get_hpd_gpio(panel->dev, p, false);
 			if (err)
-				return err;
+				goto error;
 		}
 
 		err = readx_poll_timeout(gpiod_get_value_cansleep, p->hpd_gpio,
@@ -418,13 +418,20 @@ static int panel_simple_prepare(struct drm_panel *panel)
 		if (err) {
 			dev_err(panel->dev,
 				"error waiting for hpd GPIO: %d\n", err);
-			return err;
+			goto error;
 		}
 	}
 
 	p->prepared_time = ktime_get();
 
 	return 0;
+
+error:
+	gpiod_set_value_cansleep(p->enable_gpio, 0);
+	regulator_disable(p->supply);
+	p->unprepared_time = ktime_get();
+
+	return err;
 }
 
 static int panel_simple_enable(struct drm_panel *panel)
-- 
2.30.0.284.gd98b1dd5eaa7-goog