linux-kernel - [PATCH] drm/panel: simple: Support reset GPIOs

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Date:   Fri, 13 Dec 2019 19:13:25 +0100
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     <linux-kernel@...r.kernel.org>, dri-devel@...ts.freedesktop.org,
        Paul Kocialkowski <paul.kocialkowski@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Miquel Raynal <miquel.raynal@...tlin.com>
Subject: [PATCH] drm/panel: simple: Support reset GPIOs

The panel common bindings provide a gpios-reset property which is
active low by default. Let's support it in the simple driver.

De-asserting the reset pin implies a physical high, which in turns is
a logic low.

Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
---
 drivers/gpu/drm/panel/panel-simple.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/panel/panel-simple.c b/drivers/gpu/drm/panel/panel-simple.c
index 5d487686d25c..15dd495c347d 100644
--- a/drivers/gpu/drm/panel/panel-simple.c
+++ b/drivers/gpu/drm/panel/panel-simple.c
@@ -110,6 +110,7 @@ struct panel_simple {
 	struct i2c_adapter *ddc;
 
 	struct gpio_desc *enable_gpio;
+	struct gpio_desc *reset_gpio;
 
 	struct drm_display_mode override_mode;
 };
@@ -433,12 +434,21 @@ static int panel_simple_probe(struct device *dev, const struct panel_desc *desc)
 	if (IS_ERR(panel->supply))
 		return PTR_ERR(panel->supply);
 
+	panel->reset_gpio = devm_gpiod_get_optional(dev, "reset",
+						    GPIOD_OUT_LOW);
+	if (IS_ERR(panel->reset_gpio)) {
+		err = PTR_ERR(panel->reset_gpio);
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "failed to request reset pin: %d\n", err);
+		return err;
+	}
+
 	panel->enable_gpio = devm_gpiod_get_optional(dev, "enable",
 						     GPIOD_OUT_LOW);
 	if (IS_ERR(panel->enable_gpio)) {
 		err = PTR_ERR(panel->enable_gpio);
 		if (err != -EPROBE_DEFER)
-			dev_err(dev, "failed to request GPIO: %d\n", err);
+			dev_err(dev, "failed to request enable pin: %d\n", err);
 		return err;
 	}
 
-- 
2.20.1