[PATCH 1/2] dt-bindings: display: Add King Display KD035G6-54NT panel documentation

[PATCH 1/2] dt-bindings: display: Add King Display KD035G6-54NT panel documentation

[Paul Cercueil]

The KD035G6-54NT is a 3.5" 320x240 24-bit TFT LCD panel.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 .../panel/kingdisplay,kd035g6-54nt.txt        | 27 +++++++++++++++++++
 1 file changed, 27 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt

diff --git a/Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt b/Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt
new file mode 100644
index 000000000000..a6e4a9af4925
--- /dev/null
+++ b/Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt
@@ -0,0 +1,27 @@
+King Display KD035G6-54NT 3.5" (320x240 pixels) 24-bit TFT LCD panel
+
+Required properties:
+- compatible: should be "kingdisplay,kd035g6-54nt"
+- power-supply: See panel-common.txt
+- reset-gpios: See panel-common.txt
+
+Optional properties:
+- backlight: see panel-common.txt
+
+Example:
+
+&spi {
+	display-panel {
+		compatible = "kingdisplay,kd035g6-54nt";
+		reg = <0>;
+
+		spi-max-frequency = <3125000>;
+		spi-3wire;
+		spi-cs-high;
+
+		reset-gpios = <&gpe 2 GPIO_ACTIVE_LOW>;
+
+		backlight = <&backlight>;
+		power-supply = <&ldo6>;
+	};
+};
-- 
2.21.0.593.g511ec345e18

[PATCH 2/2] drm/panel: Add Novatek NT39016 panel support

[Paul Cercueil]

Add support for display panels built around the Novatek NT39016 display
controller, as found on e.g. the King Display KD035G6-54NT 24-bit
320x240 3.5" LCD panel which equips the GCW Zero open-source handheld
gaming console.

Signed-off-by: Paul Cercueil <paul@crapouillou.net>
---
 drivers/gpu/drm/panel/Kconfig                 |   9 +
 drivers/gpu/drm/panel/Makefile                |   1 +
 drivers/gpu/drm/panel/panel-novatek-nt39016.c | 368 ++++++++++++++++++
 3 files changed, 378 insertions(+)
 create mode 100644 drivers/gpu/drm/panel/panel-novatek-nt39016.c

diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
index e281fc544742..10b411b507cc 100644
--- a/drivers/gpu/drm/panel/Kconfig
+++ b/drivers/gpu/drm/panel/Kconfig
@@ -111,6 +111,15 @@ config DRM_PANEL_LG_LG4573
 	  Say Y here if you want to enable support for LG4573 RGB panel.
 	  To compile this driver as a module, choose M here.
 
+config DRM_PANEL_NOVATEK_NT39016
+	tristate "Novatek NT39016 RGB/SPI panel"
+	depends on OF && SPI
+	depends on BACKLIGHT_CLASS_DEVICE
+	select REGMAP_SPI
+	help
+	  Say Y here if you want to enable support for the panels built
+	  around the Novatek NT39016 display controller.
+
 config DRM_PANEL_OLIMEX_LCD_OLINUXINO
 	tristate "Olimex LCD-OLinuXino panel"
 	depends on OF
diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
index 78e3dc376bdd..c2c47fc99343 100644
--- a/drivers/gpu/drm/panel/Makefile
+++ b/drivers/gpu/drm/panel/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_DRM_PANEL_INNOLUX_P079ZCA) += panel-innolux-p079zca.o
 obj-$(CONFIG_DRM_PANEL_JDI_LT070ME05000) += panel-jdi-lt070me05000.o
 obj-$(CONFIG_DRM_PANEL_KINGDISPLAY_KD097D04) += panel-kingdisplay-kd097d04.o
 obj-$(CONFIG_DRM_PANEL_LG_LG4573) += panel-lg-lg4573.o
+obj-$(CONFIG_DRM_PANEL_NOVATEK_NT39016) += panel-novatek-nt39016.o
 obj-$(CONFIG_DRM_PANEL_OLIMEX_LCD_OLINUXINO) += panel-olimex-lcd-olinuxino.o
 obj-$(CONFIG_DRM_PANEL_ORISETECH_OTM8009A) += panel-orisetech-otm8009a.o
 obj-$(CONFIG_DRM_PANEL_PANASONIC_VVX10F034N00) += panel-panasonic-vvx10f034n00.o
diff --git a/drivers/gpu/drm/panel/panel-novatek-nt39016.c b/drivers/gpu/drm/panel/panel-novatek-nt39016.c
new file mode 100644
index 000000000000..2738d145d452
--- /dev/null
+++ b/drivers/gpu/drm/panel/panel-novatek-nt39016.c
@@ -0,0 +1,368 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Novatek NT39016 TFT LCD panel driver
+ *
+ * Copyright (C) 2017, Maarten ter Huurne <maarten@treewalker.org>
+ * Copyright (C) 2019, Paul Cercueil <paul@crapouillou.net>
+ */
+
+#include <drm/drm_modes.h>
+#include <drm/drm_panel.h>
+#include <linux/backlight.h>
+#include <linux/delay.h>
+#include <linux/device.h>
+#include <linux/gpio/consumer.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/regulator/consumer.h>
+#include <linux/spi/spi.h>
+#include <uapi/linux/media-bus-format.h>
+
+
+enum nt39016_regs {
+	NT39016_REG_SYSTEM,
+	NT39016_REG_TIMING,
+	NT39016_REG_OP,
+	NT39016_REG_DATA_IN,
+	NT39016_REG_SRC_TIMING_DELAY,
+	NT39016_REG_GATE_TIMING_DELAY,
+	NT39016_REG_RESERVED,
+	NT39016_REG_INITIAL_FUNC,
+	NT39016_REG_CONTRAST,
+	NT39016_REG_BRIGHTNESS,
+	NT39016_REG_HUE_SATURATION,
+	NT39016_REG_RB_SUBCONTRAST,
+	NT39016_REG_R_SUBBRIGHTNESS,
+	NT39016_REG_B_SUBBRIGHTNESS,
+	NT39016_REG_VCOMDC,
+	NT39016_REG_VCOMAC,
+	NT39016_REG_VGAM2,
+	NT39016_REG_VGAM34,
+	NT39016_REG_VGAM56,
+	NT39016_REG_VCOMDC_TRIM = 0x1e,
+	NT39016_REG_DISPLAY_MODE = 0x20,
+};
+
+struct nt39016_panel_info {
+	struct drm_display_mode display_mode;
+	u16 width_mm, height_mm;
+	u32 bus_format, bus_flags;
+};
+
+struct nt39016 {
+	struct drm_panel drm_panel;
+	struct device *dev;
+	struct regmap *map;
+	struct regulator *supply;
+	const struct nt39016_panel_info *panel_info;
+
+	struct gpio_desc *reset_gpio;
+
+	struct backlight_device *backlight;
+};
+
+static inline struct nt39016 *to_nt39016(struct drm_panel *panel)
+{
+	return container_of(panel, struct nt39016, drm_panel);
+}
+
+#define RV(REG, VAL) { .reg = (REG), .def = (VAL), .delay_us = 2 }
+static const struct reg_sequence nt39016_panel_regs[] = {
+	RV(NT39016_REG_SYSTEM, 0x04),
+	RV(NT39016_REG_TIMING, 0x00),
+	RV(NT39016_REG_OP, 0x03),
+	RV(NT39016_REG_DATA_IN, 0xCC),
+	RV(NT39016_REG_SRC_TIMING_DELAY, 0x46),
+	RV(NT39016_REG_GATE_TIMING_DELAY, 0x05),
+	RV(NT39016_REG_RESERVED, 0x00),
+	RV(NT39016_REG_INITIAL_FUNC, 0x00),
+	RV(NT39016_REG_CONTRAST, 0x08),
+	RV(NT39016_REG_BRIGHTNESS, 0x40),
+	RV(NT39016_REG_HUE_SATURATION, 0x88),
+	RV(NT39016_REG_RB_SUBCONTRAST, 0x88),
+	RV(NT39016_REG_R_SUBBRIGHTNESS, 0x20),
+	RV(NT39016_REG_B_SUBBRIGHTNESS, 0x20),
+	RV(NT39016_REG_VCOMDC, 0x67),
+	RV(NT39016_REG_VCOMAC, 0xA4),
+	RV(NT39016_REG_VGAM2, 0x04),
+	RV(NT39016_REG_VGAM34, 0x24),
+	RV(NT39016_REG_VGAM56, 0x24),
+	RV(NT39016_REG_DISPLAY_MODE, 0x00),
+};
+#undef RV
+
+static const struct regmap_range nt39016_regmap_no_ranges[] = {
+	regmap_reg_range(0x13, 0x1D),
+	regmap_reg_range(0x1F, 0x1F),
+};
+
+static const struct regmap_access_table nt39016_regmap_access_table = {
+	.no_ranges = nt39016_regmap_no_ranges,
+	.n_no_ranges = ARRAY_SIZE(nt39016_regmap_no_ranges),
+};
+
+static const struct regmap_config nt39016_regmap_config = {
+	.reg_bits = 6,
+	.pad_bits = 2,
+	.val_bits = 8,
+
+	.max_register = NT39016_REG_DISPLAY_MODE,
+	.wr_table = &nt39016_regmap_access_table,
+	.write_flag_mask = 0x02,
+
+	.cache_type = REGCACHE_FLAT,
+};
+
+static int nt39016_prepare(struct drm_panel *drm_panel)
+{
+	struct nt39016 *panel = to_nt39016(drm_panel);
+	int err;
+
+	err = regulator_enable(panel->supply);
+	if (err) {
+		dev_err(panel->dev, "Failed to enable power supply: %i", err);
+		return err;
+	}
+
+	/*
+	 * Reset the NT39016.
+	 * The documentation says the reset pulse should be at least 40 us to
+	 * pass the glitch filter, but when testing I see some resets fail and
+	 * some succeed when using a 70 us delay, so we use 100 us instead.
+	 */
+	gpiod_set_value_cansleep(panel->reset_gpio, 1);
+	usleep_range(100, 1000);
+	gpiod_set_value_cansleep(panel->reset_gpio, 0);
+	udelay(2);
+
+	/* Init all registers. */
+	err = regmap_multi_reg_write(panel->map, nt39016_panel_regs,
+				     ARRAY_SIZE(nt39016_panel_regs));
+	if (err) {
+		dev_err(panel->dev, "Failed to init registers: %i", err);
+		goto err_disable_regulator;
+	}
+
+	return 0;
+
+err_disable_regulator:
+	regulator_disable(panel->supply);
+	return err;
+}
+
+static int nt39016_unprepare(struct drm_panel *drm_panel)
+{
+	struct nt39016 *panel = to_nt39016(drm_panel);
+
+	gpiod_set_value_cansleep(panel->reset_gpio, 1);
+
+	regulator_disable(panel->supply);
+
+	return 0;
+}
+
+static int nt39016_enable(struct drm_panel *drm_panel)
+{
+	struct nt39016 *panel = to_nt39016(drm_panel);
+	int err;
+
+	err = regmap_write(panel->map, NT39016_REG_SYSTEM, 0x07);
+	if (err) {
+		dev_err(panel->dev, "Unable to enable panel: %i", err);
+		return err;
+	}
+
+	/* Wait for the picture to be ready before enabling backlight */
+	msleep(150);
+
+	if (panel->backlight) {
+		panel->backlight->props.state &= ~BL_CORE_FBBLANK;
+		panel->backlight->props.power = FB_BLANK_UNBLANK;
+		backlight_update_status(panel->backlight);
+	}
+
+	return 0;
+}
+
+static int nt39016_disable(struct drm_panel *drm_panel)
+{
+	struct nt39016 *panel = to_nt39016(drm_panel);
+	int err;
+
+	if (panel->backlight) {
+		panel->backlight->props.power = FB_BLANK_POWERDOWN;
+		panel->backlight->props.state |= BL_CORE_FBBLANK;
+		backlight_update_status(panel->backlight);
+	}
+
+	err = regmap_write(panel->map, NT39016_REG_SYSTEM, 0x05);
+	if (err) {
+		dev_err(panel->dev, "Unable to disable panel: %i", err);
+		return err;
+	}
+
+	return 0;
+}
+
+static int nt39016_get_modes(struct drm_panel *drm_panel)
+{
+	struct nt39016 *panel = to_nt39016(drm_panel);
+	const struct nt39016_panel_info *panel_info = panel->panel_info;
+	struct drm_connector *connector = drm_panel->connector;
+	struct drm_display_mode *mode;
+
+	mode = drm_mode_duplicate(drm_panel->drm, &panel_info->display_mode);
+	if (!mode)
+		return -ENOMEM;
+
+	drm_mode_set_name(mode);
+
+	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
+	drm_mode_probed_add(connector, mode);
+
+	connector->display_info.bpc = 8;
+	connector->display_info.width_mm = panel_info->width_mm;
+	connector->display_info.height_mm = panel_info->height_mm;
+
+	drm_display_info_set_bus_formats(&connector->display_info,
+					 &panel_info->bus_format, 1);
+	connector->display_info.bus_flags = panel_info->bus_flags;
+
+	return 1;
+}
+
+static const struct drm_panel_funcs nt39016_funcs = {
+	.prepare	= nt39016_prepare,
+	.unprepare	= nt39016_unprepare,
+	.enable		= nt39016_enable,
+	.disable	= nt39016_disable,
+	.get_modes	= nt39016_get_modes,
+};
+
+static int nt39016_probe(struct spi_device *spi)
+{
+	struct device *dev = &spi->dev;
+	struct nt39016 *panel;
+	int err;
+
+	panel = devm_kzalloc(dev, sizeof(*panel), GFP_KERNEL);
+	if (!panel)
+		return -ENOMEM;
+
+	panel->dev = dev;
+	spi_set_drvdata(spi, panel);
+
+	panel->panel_info = of_device_get_match_data(dev);
+	if (!panel->panel_info)
+		return -EINVAL;
+
+	panel->supply = devm_regulator_get(dev, "power");
+	if (IS_ERR(panel->supply)) {
+		dev_err(dev, "Failed to get power supply");
+		return PTR_ERR(panel->supply);
+	}
+
+	panel->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
+	if (IS_ERR(panel->reset_gpio)) {
+		dev_err(dev, "Failed to get reset GPIO");
+		return PTR_ERR(panel->reset_gpio);
+	}
+
+	spi->bits_per_word = 8;
+	spi->mode = SPI_MODE_3 | SPI_3WIRE;
+	err = spi_setup(spi);
+	if (err) {
+		dev_err(dev, "Failed to setup SPI");
+		return err;
+	}
+
+	panel->map = devm_regmap_init_spi(spi, &nt39016_regmap_config);
+	if (IS_ERR(panel->map)) {
+		dev_err(dev, "Failed to init regmap");
+		return PTR_ERR(panel->map);
+	}
+
+	panel->backlight = devm_of_find_backlight(dev);
+	if (IS_ERR(panel->backlight)) {
+		err = PTR_ERR(panel->backlight);
+		if (err != -EPROBE_DEFER)
+			dev_err(dev, "Failed to get backlight handle");
+		return err;
+	}
+
+	drm_panel_init(&panel->drm_panel);
+	panel->drm_panel.dev = dev;
+	panel->drm_panel.funcs = &nt39016_funcs;
+
+	err = drm_panel_add(&panel->drm_panel);
+	if (err < 0) {
+		dev_err(dev, "Failed to register panel");
+		goto err_free_backlight;
+	}
+
+	return 0;
+
+err_free_backlight:
+	if (panel->backlight)
+		put_device(&panel->backlight->dev);
+
+	return err;
+}
+
+static int nt39016_remove(struct spi_device *spi)
+{
+	struct nt39016 *panel = spi_get_drvdata(spi);
+
+	drm_panel_remove(&panel->drm_panel);
+
+	nt39016_disable(&panel->drm_panel);
+	nt39016_unprepare(&panel->drm_panel);
+
+	if (panel->backlight)
+		put_device(&panel->backlight->dev);
+
+	return 0;
+}
+
+static const struct nt39016_panel_info kd035g6_info = {
+	.display_mode = {
+		.clock = 6000,
+		.hdisplay = 320,
+		.hsync_start = 320 + 10,
+		.hsync_end = 320 + 10 + 50,
+		.htotal = 320 + 10 + 50 + 20,
+		.vdisplay = 240,
+		.vsync_start = 240 + 5,
+		.vsync_end = 240 + 5 + 1,
+		.vtotal = 240 + 5 + 1 + 4,
+		.vrefresh = 60,
+		.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
+	},
+	.width_mm = 71,
+	.height_mm = 53,
+	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
+	.bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
+};
+
+static const struct of_device_id nt39016_of_match[] = {
+	{ .compatible = "kingdisplay,kd035g6-54nt", .data = &kd035g6_info },
+	{},
+};
+MODULE_DEVICE_TABLE(of, nt39016_of_match);
+
+static struct spi_driver nt39016_driver = {
+	.driver = {
+		.name = "nt39016",
+		.of_match_table = nt39016_of_match,
+	},
+	.probe = nt39016_probe,
+	.remove = nt39016_remove,
+};
+
+module_spi_driver(nt39016_driver);
+
+MODULE_AUTHOR("Maarten ter Huurne <maarten@treewalker.org>");
+MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
+MODULE_LICENSE("GPL v2");
-- 
2.21.0.593.g511ec345e18

Re: [PATCH 1/2] dt-bindings: display: Add King Display KD035G6-54NT panel documentation

[Sam Ravnborg]

Hi Paul.

As already said on irc, maybe add:

"The generic bindings for the SPI slaves documented in [1] also applies"
as we see other binding using spi already does.

Looking at: sitronix,st7789v.txt
should reg also be specified as required here?

	Sam

On Sun, Jun 02, 2019 at 06:48:43PM +0200, Paul Cercueil wrote:
> The KD035G6-54NT is a 3.5" 320x240 24-bit TFT LCD panel.
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  .../panel/kingdisplay,kd035g6-54nt.txt        | 27 +++++++++++++++++++
>  1 file changed, 27 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt
> 
> diff --git a/Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt b/Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt
> new file mode 100644
> index 000000000000..a6e4a9af4925
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/display/panel/kingdisplay,kd035g6-54nt.txt
> @@ -0,0 +1,27 @@
> +King Display KD035G6-54NT 3.5" (320x240 pixels) 24-bit TFT LCD panel
> +
> +Required properties:
> +- compatible: should be "kingdisplay,kd035g6-54nt"
> +- power-supply: See panel-common.txt
> +- reset-gpios: See panel-common.txt
> +
> +Optional properties:
> +- backlight: see panel-common.txt
> +
> +Example:
> +
> +&spi {
> +	display-panel {
> +		compatible = "kingdisplay,kd035g6-54nt";
> +		reg = <0>;
> +
> +		spi-max-frequency = <3125000>;
> +		spi-3wire;
> +		spi-cs-high;
> +
> +		reset-gpios = <&gpe 2 GPIO_ACTIVE_LOW>;
> +
> +		backlight = <&backlight>;
> +		power-supply = <&ldo6>;
> +	};
> +};
> -- 
> 2.21.0.593.g511ec345e18

Re: [PATCH 2/2] drm/panel: Add Novatek NT39016 panel support

[Sam Ravnborg]

Hi Paul.

Nice driver.
Feedback, mostly a repeat from irc, but you get it here too so others
can follow.

The backlight handling can be simplified.
Please see panel-innolux-p079zca.c as one (semi random) example.

	Sam
> 
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>

This driver is authored by Maarten ter Huurne <maarten@treewalker.org>
as well as you.
Could you get a s-o-b or at least some other formal
attribution of Maarten in the changelog.


> +
> +#include <drm/drm_modes.h>
> +#include <drm/drm_panel.h>
> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/device.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_device.h>
> +#include <linux/regmap.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +#include <uapi/linux/media-bus-format.h>

Recently (after I was there) panels sort the include in blocks like
this:

#include <linux/*>

#include <other general files from include/*>

#include <drm/*>

Within each block the header files are sorted.

For media-bus-format.h - you could use:
#include <linux/media-bus-format.h>

> +
> +static int nt39016_prepare(struct drm_panel *drm_panel)
> +{
> +	struct nt39016 *panel = to_nt39016(drm_panel);
> +	int err;
> +
> +	err = regulator_enable(panel->supply);
> +	if (err) {
> +		dev_err(panel->dev, "Failed to enable power supply: %i", err);
> +		return err;
> +	}
> +
> +	/*
> +	 * Reset the NT39016.
> +	 * The documentation says the reset pulse should be at least 40 us to
> +	 * pass the glitch filter, but when testing I see some resets fail and
> +	 * some succeed when using a 70 us delay, so we use 100 us instead.
> +	 */
> +	gpiod_set_value_cansleep(panel->reset_gpio, 1);
> +	usleep_range(100, 1000);
> +	gpiod_set_value_cansleep(panel->reset_gpio, 0);
> +	udelay(2);
> +
> +	/* Init all registers. */
> +	err = regmap_multi_reg_write(panel->map, nt39016_panel_regs,
> +				     ARRAY_SIZE(nt39016_panel_regs));

Nice!

> +	if (err) {
> +		dev_err(panel->dev, "Failed to init registers: %i", err);

Maybe it is just me, but I wonder why %i and not %d?
You are consistent which is good.
But I saw no other panle drivers use %i, so consider to do like the
rest.


> +		goto err_disable_regulator;
> +	}
> +
> +	return 0;
> +
> +err_disable_regulator:
> +	regulator_disable(panel->supply);
> +	return err;
> +}
> +
> +static int nt39016_unprepare(struct drm_panel *drm_panel)
> +{
> +	struct nt39016 *panel = to_nt39016(drm_panel);
> +
> +	gpiod_set_value_cansleep(panel->reset_gpio, 1);
> +
> +	regulator_disable(panel->supply);
> +
> +	return 0;
> +}
> +
> +static int nt39016_enable(struct drm_panel *drm_panel)
> +{
> +	struct nt39016 *panel = to_nt39016(drm_panel);
> +	int err;
> +
> +	err = regmap_write(panel->map, NT39016_REG_SYSTEM, 0x07);
> +	if (err) {
> +		dev_err(panel->dev, "Unable to enable panel: %i", err);
> +		return err;
> +	}
> +
> +	/* Wait for the picture to be ready before enabling backlight */
> +	msleep(150);
> +
> +	if (panel->backlight) {
> +		panel->backlight->props.state &= ~BL_CORE_FBBLANK;
> +		panel->backlight->props.power = FB_BLANK_UNBLANK;
> +		backlight_update_status(panel->backlight);
> +	}
> +
> +	return 0;
> +}
> +
> +static int nt39016_disable(struct drm_panel *drm_panel)
> +{
> +	struct nt39016 *panel = to_nt39016(drm_panel);
> +	int err;
> +
> +	if (panel->backlight) {
> +		panel->backlight->props.power = FB_BLANK_POWERDOWN;
> +		panel->backlight->props.state |= BL_CORE_FBBLANK;
> +		backlight_update_status(panel->backlight);
> +	}
> +
> +	err = regmap_write(panel->map, NT39016_REG_SYSTEM, 0x05);
> +	if (err) {
> +		dev_err(panel->dev, "Unable to disable panel: %i", err);
> +		return err;
> +	}
> +
> +	return 0;
> +}
Can we get some nice constants for 0x04, 0x05 and 0x07?
(All values written to NT39016_REG_SYSTEM).

> +
> +static int nt39016_get_modes(struct drm_panel *drm_panel)
> +{
> +	struct nt39016 *panel = to_nt39016(drm_panel);
> +	const struct nt39016_panel_info *panel_info = panel->panel_info;
> +	struct drm_connector *connector = drm_panel->connector;
> +	struct drm_display_mode *mode;
> +
> +	mode = drm_mode_duplicate(drm_panel->drm, &panel_info->display_mode);
> +	if (!mode)
> +		return -ENOMEM;
> +
> +	drm_mode_set_name(mode);
> +
> +	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> +	drm_mode_probed_add(connector, mode);
> +
> +	connector->display_info.bpc = 8;
> +	connector->display_info.width_mm = panel_info->width_mm;
> +	connector->display_info.height_mm = panel_info->height_mm;
> +
> +	drm_display_info_set_bus_formats(&connector->display_info,
> +					 &panel_info->bus_format, 1);
> +	connector->display_info.bus_flags = panel_info->bus_flags;
> +
> +	return 1;
> +}
> +
> +static const struct drm_panel_funcs nt39016_funcs = {
> +	.prepare	= nt39016_prepare,
> +	.unprepare	= nt39016_unprepare,
> +	.enable		= nt39016_enable,
> +	.disable	= nt39016_disable,
> +	.get_modes	= nt39016_get_modes,
> +};
> +
> +static int nt39016_probe(struct spi_device *spi)
> +{
> +	struct device *dev = &spi->dev;
> +	struct nt39016 *panel;
> +	int err;
> +
> +	panel = devm_kzalloc(dev, sizeof(*panel), GFP_KERNEL);
> +	if (!panel)
> +		return -ENOMEM;
> +
> +	panel->dev = dev;
> +	spi_set_drvdata(spi, panel);
> +
> +	panel->panel_info = of_device_get_match_data(dev);
> +	if (!panel->panel_info)
> +		return -EINVAL;
> +
> +	panel->supply = devm_regulator_get(dev, "power");
> +	if (IS_ERR(panel->supply)) {
> +		dev_err(dev, "Failed to get power supply");
> +		return PTR_ERR(panel->supply);
> +	}
> +
> +	panel->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(panel->reset_gpio)) {
> +		dev_err(dev, "Failed to get reset GPIO");
> +		return PTR_ERR(panel->reset_gpio);
> +	}
> +
> +	spi->bits_per_word = 8;
> +	spi->mode = SPI_MODE_3 | SPI_3WIRE;
> +	err = spi_setup(spi);
> +	if (err) {
> +		dev_err(dev, "Failed to setup SPI");
> +		return err;
> +	}
> +
> +	panel->map = devm_regmap_init_spi(spi, &nt39016_regmap_config);
> +	if (IS_ERR(panel->map)) {
> +		dev_err(dev, "Failed to init regmap");
> +		return PTR_ERR(panel->map);
> +	}
> +
> +	panel->backlight = devm_of_find_backlight(dev);
> +	if (IS_ERR(panel->backlight)) {
> +		err = PTR_ERR(panel->backlight);
> +		if (err != -EPROBE_DEFER)
> +			dev_err(dev, "Failed to get backlight handle");
> +		return err;
> +	}
> +
> +	drm_panel_init(&panel->drm_panel);
> +	panel->drm_panel.dev = dev;
> +	panel->drm_panel.funcs = &nt39016_funcs;
> +
> +	err = drm_panel_add(&panel->drm_panel);
> +	if (err < 0) {
> +		dev_err(dev, "Failed to register panel");
> +		goto err_free_backlight;
> +	}
> +
> +	return 0;
> +
> +err_free_backlight:
> +	if (panel->backlight)
> +		put_device(&panel->backlight->dev);
When devm_xxx is used for backlight, the above is not needed.

Consider to write error codes for all what can fail in probe().
It may help you later when diving into logs.

> +
> +static int nt39016_remove(struct spi_device *spi)
> +{
> +	struct nt39016 *panel = spi_get_drvdata(spi);
> +
> +	drm_panel_remove(&panel->drm_panel);
> +
> +	nt39016_disable(&panel->drm_panel);
> +	nt39016_unprepare(&panel->drm_panel);
> +
> +	if (panel->backlight)
> +		put_device(&panel->backlight->dev);
Not needed.
> +
> +	return 0;
> +}
> +
> +static const struct nt39016_panel_info kd035g6_info = {
> +	.display_mode = {
> +		.clock = 6000,
> +		.hdisplay = 320,
> +		.hsync_start = 320 + 10,
> +		.hsync_end = 320 + 10 + 50,
> +		.htotal = 320 + 10 + 50 + 20,
> +		.vdisplay = 240,
> +		.vsync_start = 240 + 5,
> +		.vsync_end = 240 + 5 + 1,
> +		.vtotal = 240 + 5 + 1 + 4,
> +		.vrefresh = 60,
> +		.flags = DRM_MODE_FLAG_NHSYNC | DRM_MODE_FLAG_NVSYNC,
> +	},
> +	.width_mm = 71,
> +	.height_mm = 53,
> +	.bus_format = MEDIA_BUS_FMT_RGB888_1X24,
> +	.bus_flags = DRM_BUS_FLAG_PIXDATA_NEGEDGE,
> +};
Everything specified - good!

> +
> +static const struct of_device_id nt39016_of_match[] = {
> +	{ .compatible = "kingdisplay,kd035g6-54nt", .data = &kd035g6_info },
> +	{},
Maybe write { /* sentinel */ } like many other drivers.
> +};
> +MODULE_DEVICE_TABLE(of, nt39016_of_match);
> +
> +static struct spi_driver nt39016_driver = {
> +	.driver = {
> +		.name = "nt39016",
> +		.of_match_table = nt39016_of_match,
> +	},
> +	.probe = nt39016_probe,
> +	.remove = nt39016_remove,
> +};
> +
> +module_spi_driver(nt39016_driver);
> +
> +MODULE_AUTHOR("Maarten ter Huurne <maarten@treewalker.org>");
> +MODULE_AUTHOR("Paul Cercueil <paul@crapouillou.net>");
> +MODULE_LICENSE("GPL v2");

Re: [PATCH 2/2] drm/panel: Add Novatek NT39016 panel support

[Maarten ter Huurne]

On Sunday, 2 June 2019 20:44:53 CEST Sam Ravnborg wrote:

> > Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> 
> This driver is authored by Maarten ter Huurne <maarten@treewalker.org>
> as well as you.
> Could you get a s-o-b or at least some other formal
> attribution of Maarten in the changelog.

This is based on a driver I wrote for the GCW Zero back when we were 
using fbdev. Paul updated it for drm and did additional cleanups.

Signed-off-by: Maarten ter Huurne <maarten@treewalker.org>

Bye,
		Maarten