build/patch/kernel/archive/sunxi-6.5/patches.megous/drm-panel-st7703-Improve-the-power-up-down-sequence-of-the-pane.patch

From 96d543355fedff5c827ff5e5125fff3e1ebb522e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Jirman?= <megi@xff.cz>
Date: Sun, 5 Jul 2020 15:55:46 +0200
Subject: [PATCH 205/464] drm/panel: st7703: Improve the power up/down sequence
 of the panel

The datasheet specifies that there needs to be 120ms delay after
the sleep out command, not after reset as the driver assumes.

The delay between init commands and the sleep out is not necessary.

The datasheet also specifies that it's better to keep reset asserted
while powering up the supplies, and that IOVCC should be enabled
first.

There also needs to be a delay after enabling the supplies and
before deasserting the reset. The datasheet specifies 1ms after
the supplies reach the required voltage. Use 10-20ms to give the
power supplies some time to reach the required voltage, too.

After issuing SLEEP IN, it's necessary to let the controller complete
the blanking sequence and drain the charge from the panel. (According
to the datasheet.)

This fixes panel initialization failures during resume from sleep
on PinePhone.

Signed-off-by: Ondrej Jirman <megi@xff.cz>
---
 drivers/gpu/drm/panel/panel-sitronix-st7703.c | 35 ++++++++++---------
 1 file changed, 18 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/panel/panel-sitronix-st7703.c b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
index 3aa31f3d6157..6d9f823e7517 100644
--- a/drivers/gpu/drm/panel/panel-sitronix-st7703.c
+++ b/drivers/gpu/drm/panel/panel-sitronix-st7703.c
@@ -276,7 +276,6 @@ static int xbd599_init_sequence(struct st7703 *ctx)
 	mipi_dsi_dcs_write_seq(dsi, ST7703_CMD_SETBGP,
 			       0x07, /* VREF_SEL = 4.2V */
 			       0x07  /* NVREF_SEL = 4.2V */);
-	msleep(20);
 
 	mipi_dsi_dcs_write_seq(dsi, ST7703_CMD_SETVCOM,
 			       0x2C, /* VCOMDC_F = -0.67V */
@@ -445,16 +444,14 @@ static int st7703_enable(struct drm_panel *panel)
 		return ret;
 	}
 
-	msleep(20);
-
 	ret = mipi_dsi_dcs_exit_sleep_mode(dsi);
 	if (ret < 0) {
 		dev_err(ctx->dev, "Failed to exit sleep mode: %d\n", ret);
 		return ret;
 	}
 
-	/* Panel is operational 120 msec after reset */
-	msleep(60);
+	/* Display on can be issued 120 msec after sleep out */
+	msleep(120);
 
 	ret = mipi_dsi_dcs_set_display_on(dsi);
 	if (ret)
@@ -479,6 +476,9 @@ static int st7703_disable(struct drm_panel *panel)
 	if (ret < 0)
 		dev_err(ctx->dev, "Failed to enter sleep mode: %d\n", ret);
 
+	/* Display needs to be drained of charge, in order to work correctly on next power on. */
+	msleep(120);
+
 	return 0;
 }
 
@@ -506,29 +506,30 @@ static int st7703_prepare(struct drm_panel *panel)
 		return 0;
 
 	dev_dbg(ctx->dev, "Resetting the panel\n");
-	ret = regulator_enable(ctx->vcc);
+	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
+
+	ret = regulator_enable(ctx->iovcc);
 	if (ret < 0) {
-		dev_err(ctx->dev, "Failed to enable vcc supply: %d\n", ret);
+		dev_err(ctx->dev, "Failed to enable iovcc supply: %d\n", ret);
 		return ret;
 	}
-	ret = regulator_enable(ctx->iovcc);
+
+	ret = regulator_enable(ctx->vcc);
 	if (ret < 0) {
-		dev_err(ctx->dev, "Failed to enable iovcc supply: %d\n", ret);
-		goto disable_vcc;
+		dev_err(ctx->dev, "Failed to enable vcc supply: %d\n", ret);
+		regulator_disable(ctx->iovcc);
+		return ret;
 	}
 
-	gpiod_set_value_cansleep(ctx->reset_gpio, 1);
-	usleep_range(20, 40);
+	/* Give power supplies time to stabilize before deasserting reset. */
+	usleep_range(10000, 20000);
+
 	gpiod_set_value_cansleep(ctx->reset_gpio, 0);
-	msleep(20);
+	usleep_range(15000, 20000);
 
 	ctx->prepared = true;
 
 	return 0;
-
-disable_vcc:
-	regulator_disable(ctx->vcc);
-	return ret;
 }
 
 static const u32 mantix_bus_formats[] = {
-- 
2.34.1