linux-kernel - [RFC PATCH v1 2/3] drm/panel: mantix: Fix panel reset

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Date:   Mon, 21 Sep 2020 18:55:51 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [RFC PATCH v1 2/3] drm/panel: mantix: Fix panel reset

The mantix panel needs two reset lines (RESX and TP_RSTN) deasserted to
output an image. Only deasserting RESX is not enough and the display
will stay blank. Deassert in prepare() and assert in unprepare() to keep
device held in reset when off.

Signed-off-by: Guido Günther <agx@...xcpu.org>
---
 .../gpu/drm/panel/panel-mantix-mlaf057we51.c  | 37 ++++++++++++-------
 1 file changed, 24 insertions(+), 13 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c b/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c
index 4a7fbf64bb7a..29d28c63bb72 100644
--- a/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c
+++ b/drivers/gpu/drm/panel/panel-mantix-mlaf057we51.c
@@ -23,10 +23,13 @@
 #define MANTIX_CMD_OTP_STOP_RELOAD_MIPI 0x41
 #define MANTIX_CMD_INT_CANCEL           0x4C
 
+#define MANTIX_NUM_RESETS 2
+
 struct mantix {
 	struct device *dev;
 	struct drm_panel panel;
-	struct gpio_desc *reset_gpio;
+	/* RESX and TP_RSTN */
+	struct gpio_descs *reset_gpios;
 
 	struct regulator *avdd;
 	struct regulator *avee;
@@ -122,8 +125,13 @@ static int mantix_disable(struct drm_panel *panel)
 
 static int mantix_unprepare(struct drm_panel *panel)
 {
+	DECLARE_BITMAP(asserted_values, BITS_PER_TYPE(1));
 	struct mantix *ctx = panel_to_mantix(panel);
 
+	gpiod_set_array_value_cansleep(ctx->reset_gpios->ndescs,
+				       ctx->reset_gpios->desc,
+				       ctx->reset_gpios->info, asserted_values);
+
 	regulator_disable(ctx->avee);
 	regulator_disable(ctx->avdd);
 	/* T11 */
@@ -137,6 +145,7 @@ static int mantix_unprepare(struct drm_panel *panel)
 
 static int mantix_prepare(struct drm_panel *panel)
 {
+	DECLARE_BITMAP(deasserted_values, BITS_PER_TYPE(0));
 	struct mantix *ctx = panel_to_mantix(panel);
 	int ret;
 
@@ -165,14 +174,11 @@ static int mantix_prepare(struct drm_panel *panel)
 		return ret;
 	}
 
-	/* T3+T5 */
-	usleep_range(10000, 12000);
-
-	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
-	usleep_range(5150, 7000);
-
-	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
-
+	/* T3 + T4 + time for voltage to become stable: */
+	usleep_range(6000, 7000);
+	gpiod_set_array_value_cansleep(ctx->reset_gpios->ndescs,
+				       ctx->reset_gpios->desc,
+				       ctx->reset_gpios->info, deasserted_values);
 	/* T6 */
 	msleep(50);
 
@@ -236,10 +242,15 @@ static int mantix_probe(struct mipi_dsi_device *dsi)
 	if (!ctx)
 		return -ENOMEM;
 
-	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
-	if (IS_ERR(ctx->reset_gpio)) {
-		dev_err(dev, "cannot get reset gpio\n");
-		return PTR_ERR(ctx->reset_gpio);
+	ctx->reset_gpios = devm_gpiod_get_array(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(ctx->reset_gpios)) {
+		dev_err(dev, "cannot get reset gpios\n");
+		return PTR_ERR(ctx->reset_gpios);
+	}
+
+	if (ctx->reset_gpios->ndescs != MANTIX_NUM_RESETS) {
+		dev_err(dev, "Need exactly %d reset-gpios\n", MANTIX_NUM_RESETS);
+		return -EINVAL;
 	}
 
 	mipi_dsi_set_drvdata(dsi, ctx);
-- 
2.26.2