Date:	Tue, 23 Dec 2014 11:38:43 +0100
From:	Andrzej Hajda <a.hajda@...sung.com>
To:	Liu Ying <Ying.Liu@...escale.com>, dri-devel@...ts.freedesktop.org
Cc:	devicetree@...r.kernel.org, linux@....linux.org.uk,
	kernel@...gutronix.de, linux-kernel@...r.kernel.org,
	mturquette@...aro.org, linux-arm-kernel@...ts.infradead.org,
	andyshrk@...il.com
Subject: Re: [PATCH RFC v3 13/18] drm: panel: Add support for Himax HX8369A
 MIPI DSI panel

Hi Liu Ying,

On 12/23/2014 04:46 AM, Liu Ying wrote:
> This patch adds support for Himax HX8369A MIPI DSI panel.
> 
> Signed-off-by: Liu Ying <Ying.Liu@...escale.com>
> ---
> v2->v3:
>  * Sort the included header files alphabetically.
> 
> v1->v2:
>  * Address almost all comments from Thierry Reding.
>  * Remove several DT properties as they can be implied by the compatible string.
>  * Add the HIMAX/himax prefixes to the driver's Kconfig name and driver name.
>  * Move the driver's Makefile entry place to sort the entries alphabetically.
>  * Reuse several standard DCS functions instead of inventing wheels.
>  * Move the panel resetting and power logics to the driver probe/remove stages.
>    This may simplify panel prepare/unprepare hooks. The power consumption should
>    not change a lot at DPMS since the panel enters sleep mode at that time.

What kind of issues did you have with reset/power logic in
prepare/unprepare? As I see it should be just a matter of moving
power on/off functions to prepare/unprepare, am I right?

>  * Add the module author.
>  * Other minor changes, such as coding style issues.
> 
>  .../devicetree/bindings/panel/himax,hx8369a.txt    |  41 ++
>  drivers/gpu/drm/panel/Kconfig                      |   5 +
>  drivers/gpu/drm/panel/Makefile                     |   1 +
>  drivers/gpu/drm/panel/panel-himax-hx8369a.c        | 573 +++++++++++++++++++++
>  4 files changed, 620 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/panel/himax,hx8369a.txt
>  create mode 100644 drivers/gpu/drm/panel/panel-himax-hx8369a.c
> 
> diff --git a/Documentation/devicetree/bindings/panel/himax,hx8369a.txt b/Documentation/devicetree/bindings/panel/himax,hx8369a.txt
> new file mode 100644
> index 0000000..36a2f11
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/panel/himax,hx8369a.txt
> @@ -0,0 +1,41 @@
> +Himax HX8369A WVGA 16.7M color TFT single chip driver with internal GRAM
> +
> +Himax HX8369A is a WVGA resolution driving controller.
> +It is designed to provide a single chip solution that combines a source
> +driver and power supply circuits to drive a TFT dot matrix LCD with
> +480RGBx864 dots at the maximum.
> +
> +The HX8369A supports several interface modes, including MPU MIPI DBI Type
> +A/B mode, MIPI DPI/DBI Type C mode, MIPI DSI video mode, MIPI DSI command
> +mode and MDDI mode. The interface mode is selected by the external hardware
> +pins BS[3:0].
> +
> +Currently, only the MIPI DSI video mode is supported.
> +
> +Required properties:
> +  - compatible: should be a panel's compatible string
> +  - reg: the virtual channel number of a DSI peripheral as described in [1]
> +  - reset-gpios: a GPIO spec for the reset pin
> +
> +Optional properties:
> +  - vdd1-supply: I/O and interface power supply
> +  - vdd2-supply: analog power supply
> +  - vdd3-supply: logic power supply
> +  - dsi-vcc-supply: DSI and MDDI power supply
> +  - vpp-supply: OTP programming voltage
> +  - bs0-gpios: a GPIO spec for the pin BS0
> +  - bs1-gpios: a GPIO spec for the pin BS1
> +  - bs2-gpios: a GPIO spec for the pin BS2
> +  - bs3-gpios: a GPIO spec for the pin BS3

I wonder if it wouldn't be better to replace it by gpio list, sth like:
     - bs-gpios: list of four GPIO specs for BS0-BS3 pins

At least documentation suggests it [1], it also allows to omit some pins
if necessary, but it is just suggestion.

[1]: Documentation/devicetree/bindings/gpio/gpio.txt

> +
> +[1] Documentation/devicetree/bindings/mipi/dsi/mipi-dsi-bus.txt
> +
> +Example:
> +	panel {
> +		compatible = "truly,tft480800-16-e-dsi";
> +		reg = <0>;
> +		pinctrl-names = "default";
> +		pinctrl-0 = <&pinctrl_mipi_panel>;
> +		reset-gpios = <&gpio6 11 GPIO_ACTIVE_LOW>;
> +		bs2-gpios = <&gpio6 14 GPIO_ACTIVE_HIGH>;
> +	};
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 024e98e..81b0bf0 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -16,6 +16,11 @@ config DRM_PANEL_SIMPLE
>  	  that it can be automatically turned off when the panel goes into a
>  	  low power state.
>  
> +config DRM_PANEL_HIMAX_HX8369A
> +	tristate "Himax HX8369A panel"
> +	depends on OF
> +	select DRM_MIPI_DSI
> +
>  config DRM_PANEL_LD9040
>  	tristate "LD9040 RGB/SPI panel"
>  	depends on OF && SPI
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index 4b2a043..d5dbe06 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -1,4 +1,5 @@
>  obj-$(CONFIG_DRM_PANEL_SIMPLE) += panel-simple.o
> +obj-$(CONFIG_DRM_PANEL_HIMAX_HX8369A) += panel-himax-hx8369a.o
>  obj-$(CONFIG_DRM_PANEL_LD9040) += panel-ld9040.o
>  obj-$(CONFIG_DRM_PANEL_S6E8AA0) += panel-s6e8aa0.o
>  obj-$(CONFIG_DRM_PANEL_SHARP_LQ101R1SX01) += panel-sharp-lq101r1sx01.o
> diff --git a/drivers/gpu/drm/panel/panel-himax-hx8369a.c b/drivers/gpu/drm/panel/panel-himax-hx8369a.c
> new file mode 100644
> index 0000000..6efce8e
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-himax-hx8369a.c
> @@ -0,0 +1,573 @@
> +/*
> + * Himax HX8369A panel driver.
> + *
> + * Copyright (C) 2011-2014 Freescale Semiconductor, Inc.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This driver is based on Samsung s6e8aa0 panel driver.
> + */
> +
> +#include <drm/drmP.h>
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_panel.h>
> +
> +#include <linux/gpio/consumer.h>
> +#include <linux/of_device.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include <video/mipi_display.h>
> +#include <video/of_videomode.h>
> +#include <video/videomode.h>
> +
> +#define WRDISBV		0x51
> +#define WRCTRLD		0x53
> +#define WRCABC		0x55
> +#define SETPOWER	0xb1
> +#define SETDISP		0xb2
> +#define SETCYC		0xb4
> +#define SETVCOM		0xb6
> +#define SETEXTC		0xb9
> +#define SETMIPI		0xba
> +#define SETPANEL	0xcc
> +#define SETGIP		0xd5
> +#define SETGAMMA	0xe0
> +
> +#define HX8369A_MIN_BRIGHTNESS	0x00
> +#define HX8369A_MAX_BRIGHTNESS	0xff
> +
> +enum hx8369a_mpu_interface {
> +	HX8369A_DBI_TYPE_A_8BIT,
> +	HX8369A_DBI_TYPE_A_9BIT,
> +	HX8369A_DBI_TYPE_A_16BIT,
> +	HX8369A_DBI_TYPE_A_18BIT,
> +	HX8369A_DBI_TYPE_B_8BIT,
> +	HX8369A_DBI_TYPE_B_9BIT,
> +	HX8369A_DBI_TYPE_B_16BIT,
> +	HX8369A_DBI_TYPE_B_18BIT,
> +	HX8369A_DSI_CMD_MODE,
> +	HX8369A_DBI_TYPE_B_24BIT,
> +	HX8369A_DSI_VIDEO_MODE,
> +	HX8369A_MDDI,
> +	HX8369A_DPI_DBI_TYPE_C_OPT1,
> +	HX8369A_DPI_DBI_TYPE_C_OPT2,
> +	HX8369A_DPI_DBI_TYPE_C_OPT3
> +};
> +
> +enum hx8369a_resolution {
> +	HX8369A_RES_480_864,
> +	HX8369A_RES_480_854,
> +	HX8369A_RES_480_800,
> +	HX8369A_RES_480_640,
> +	HX8369A_RES_360_640,
> +	HX8369A_RES_480_720,
> +};
> +
> +struct hx8369a_panel_desc {
> +	const struct drm_display_mode *mode;
> +
> +	/* ms */
> +	unsigned int power_on_delay;
> +	unsigned int reset_delay;
> +
> +	unsigned int dsi_lanes;
> +};
> +
> +struct hx8369a {
> +	struct device *dev;
> +	struct drm_panel panel;
> +
> +	const struct hx8369a_panel_desc *pd;
> +
> +	struct regulator_bulk_data supplies[5];
> +	struct gpio_desc *reset_gpio;
> +	struct gpio_desc *bs_gpio[4];
> +	u8 res_sel;
> +};
> +
> +static inline struct hx8369a *panel_to_hx8369a(struct drm_panel *panel)
> +{
> +	return container_of(panel, struct hx8369a, panel);
> +}
> +
> +static void hx8369a_dcs_write(struct hx8369a *ctx, const char *func,
> +			      const void *data, size_t len)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	ssize_t ret;
> +
> +	ret = mipi_dsi_dcs_write_buffer(dsi, data, len);
> +	if (ret < 0)
> +		dev_err(ctx->dev, "%s failed: %d\n", func, ret);

Your only reaction to transmission errors is to log error, no error
propagation. I think it is not the best approach. I suggest to implement
error propagation either the way I did in s6e8aa0, either the way
Thierry suggests. Of course I prefer my method as it significantly
reduces code bloat due to error checking, but it is up to you.

> +}
> +
> +#define hx8369a_dcs_write_seq(ctx, seq...) \
> +({ \
> +	const u8 d[] = { seq }; \
> +	BUILD_BUG_ON_MSG(ARRAY_SIZE(d) > 64, "DCS sequence too big for stack"); \
> +	hx8369a_dcs_write(ctx, __func__, d, ARRAY_SIZE(d)); \
> +})
> +
> +#define hx8369a_dcs_write_seq_static(ctx, seq...) \
> +({ \
> +	static const u8 d[] = { seq }; \
> +	hx8369a_dcs_write(ctx, __func__, d, ARRAY_SIZE(d)); \
> +})
> +
> +static void hx8369a_dsi_set_display_related_register(struct hx8369a *ctx)
> +{
> +	u8 sec_p = (ctx->res_sel << 4) | 0x03;
> +
> +	hx8369a_dcs_write_seq(ctx, SETDISP, 0x00, sec_p, 0x03,
> +		0x03, 0x70, 0x00, 0xff, 0x00, 0x00, 0x00, 0x00,
> +		0x03, 0x03, 0x00, 0x01);
> +}
> +
> +static void hx8369a_dsi_set_display_waveform_cycle(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETCYC, 0x00, 0x1d, 0x5f, 0x0e, 0x06);
> +}
> +
> +static void hx8369a_dsi_set_gip(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETGIP, 0x00, 0x04, 0x03, 0x00, 0x01,
> +				0x05, 0x1c, 0x70, 0x01, 0x03, 0x00, 0x00, 0x40,
> +				0x06, 0x51, 0x07, 0x00, 0x00, 0x41, 0x06, 0x50,
> +				0x07, 0x07, 0x0f, 0x04);
> +}
> +
> +static void hx8369a_dsi_set_power(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETPOWER, 0x01, 0x00, 0x34, 0x06, 0x00,
> +				0x0f, 0x0f, 0x2a, 0x32, 0x3f, 0x3f, 0x07, 0x3a,
> +				0x01, 0xe6, 0xe6, 0xe6, 0xe6, 0xe6);
> +}
> +
> +static void hx8369a_dsi_set_vcom_voltage(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETVCOM, 0x56, 0x56);
> +}
> +
> +static void hx8369a_dsi_set_panel(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETPANEL, 0x02);
> +}
> +
> +static void hx8369a_dsi_set_gamma_curve(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETGAMMA, 0x00, 0x1d, 0x22, 0x38, 0x3d,
> +				0x3f, 0x2e, 0x4a, 0x06, 0x0d, 0x0f, 0x13, 0x15,
> +				0x13, 0x16, 0x10, 0x19, 0x00, 0x1d, 0x22, 0x38,
> +				0x3d, 0x3f, 0x2e, 0x4a, 0x06, 0x0d, 0x0f, 0x13,
> +				0x15, 0x13, 0x16, 0x10, 0x19);
> +}
> +
> +static void hx8369a_dsi_set_mipi(struct hx8369a *ctx)
> +{
> +	u8 eleventh_p = ctx->pd->dsi_lanes == 2 ? 0x11 : 0x10;
> +
> +	hx8369a_dcs_write_seq(ctx, SETMIPI, 0x00, 0xa0, 0xc6, 0x00, 0x0a, 0x00,
> +			0x10, 0x30, 0x6f, 0x02, eleventh_p, 0x18, 0x40);
> +}
> +
> +static void hx8369a_dsi_set_interface_pixel_fomat(struct hx8369a *ctx)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	u8 format;
> +	int ret;
> +
> +	if (dsi->format == MIPI_DSI_FMT_RGB888)
> +		format = 0x77;
> +	else if (dsi->format == MIPI_DSI_FMT_RGB565)
> +		format = 0x55;
> +	else
> +		format = 0x66;

Just nitpick, switch fits better here.

> +
> +	ret = mipi_dsi_dcs_set_pixel_format(dsi, format);
> +	if (ret < 0)
> +		dev_err(ctx->dev, "%s failed: %d\n", __func__, ret);
> +}
> +
> +static void hx8369a_dsi_set_column_address(struct hx8369a *ctx)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	const struct drm_display_mode *mode = ctx->pd->mode;
> +	int ret;
> +
> +	ret = mipi_dsi_dcs_set_column_address(dsi, 0, mode->hdisplay - 1);
> +	if (ret < 0)
> +		dev_err(ctx->dev, "%s failed: %d\n", __func__, ret);
> +}
> +
> +static void hx8369a_dsi_set_page_address(struct hx8369a *ctx)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	const struct drm_display_mode *mode = ctx->pd->mode;
> +	int ret;
> +
> +	ret = mipi_dsi_dcs_set_page_address(dsi, 0, mode->vdisplay - 1);
> +	if (ret < 0)
> +		dev_err(ctx->dev, "%s failed: %d\n", __func__, ret);
> +}
> +
> +static void hx8369a_dsi_write_display_brightness(struct hx8369a *ctx, u8 brightness)
> +{
> +	hx8369a_dcs_write_seq(ctx, WRDISBV, brightness);
> +}
> +
> +static void hx8369a_dsi_write_cabc(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, WRCABC, 0x01);
> +}
> +
> +static void hx8369a_dsi_write_control_display(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, WRCTRLD, 0x24);
> +}
> +
> +static void hx8369a_dsi_panel_init(struct hx8369a *ctx)
> +{
> +	hx8369a_dsi_set_display_related_register(ctx);
> +	hx8369a_dsi_set_display_waveform_cycle(ctx);
> +	hx8369a_dsi_set_gip(ctx);
> +	hx8369a_dsi_set_power(ctx);
> +	hx8369a_dsi_set_vcom_voltage(ctx);
> +	hx8369a_dsi_set_panel(ctx);
> +	hx8369a_dsi_set_gamma_curve(ctx);
> +	hx8369a_dsi_set_mipi(ctx);
> +	hx8369a_dsi_set_interface_pixel_fomat(ctx);
> +	hx8369a_dsi_set_column_address(ctx);
> +	hx8369a_dsi_set_page_address(ctx);
> +	hx8369a_dsi_write_cabc(ctx);
> +	hx8369a_dsi_write_control_display(ctx);
> +}
> +
> +static void hx8369a_dsi_set_extension_command(struct hx8369a *ctx)
> +{
> +	hx8369a_dcs_write_seq_static(ctx, SETEXTC, 0xff, 0x83, 0x69);
> +}
> +
> +static void hx8369a_dsi_set_maximum_return_packet_size(struct hx8369a *ctx,
> +						       u16 size)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	int ret;
> +
> +	ret = mipi_dsi_set_maximum_return_packet_size(dsi, size);
> +	if (ret < 0)
> +		dev_err(ctx->dev,
> +			"error %d setting maximum return packet size to %d\n",
> +			ret, size);
> +}
> +
> +static int hx8369a_dsi_set_sequence(struct hx8369a *ctx)
> +{
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	int ret;
> +
> +	hx8369a_dsi_set_extension_command(ctx);
> +	hx8369a_dsi_set_maximum_return_packet_size(ctx, 4);
> +	hx8369a_dsi_panel_init(ctx);
> +
> +	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;
> +	}
> +
> +	ret = mipi_dsi_dcs_set_display_on(dsi);
> +	if (ret < 0) {
> +		dev_err(ctx->dev, "failed to set display on: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * It's necessary to wait 120msec after sending the Sleep Out
> +	 * command before Sleep In command can be sent, according to
> +	 * the HX8369A data sheet.
> +	 */
> +	msleep(120);
> +
> +	return 0;
> +}
> +
> +static int hx8369a_dsi_disable(struct drm_panel *panel)
> +{
> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
> +	hx8369a_dsi_write_display_brightness(ctx, HX8369A_MIN_BRIGHTNESS);
> +	return 0;
> +}
> +
> +static int hx8369a_dsi_unprepare(struct drm_panel *panel)
> +{
> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
> +	struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> +	int ret;
> +
> +	ret = mipi_dsi_dcs_enter_sleep_mode(dsi);
> +	if (ret < 0) {
> +		dev_err(ctx->dev, "failed to enter sleep mode: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ret = mipi_dsi_dcs_set_display_off(dsi);
> +	if (ret < 0) {
> +		dev_err(ctx->dev, "failed to set display off: %d\n", ret);
> +		return ret;
> +	}
> +
> +	/*
> +	 * This is to allow time for the supply voltages and clock
> +	 * circuits to stablize, according to the HX8369A data sheet.
> +	 */
> +	msleep(5);
> +
> +	return ret;
> +}
> +
> +static int hx8369a_dsi_prepare(struct drm_panel *panel)
> +{
> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
> +	return hx8369a_dsi_set_sequence(ctx);
> +}
> +
> +static int hx8369a_dsi_enable(struct drm_panel *panel)
> +{
> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
> +	hx8369a_dsi_write_display_brightness(ctx, HX8369A_MAX_BRIGHTNESS);
> +	return 0;
> +}
> +
> +static int hx8369a_get_modes(struct drm_panel *panel)
> +{
> +	struct drm_connector *connector = panel->connector;
> +	struct drm_device *drm = panel->drm;
> +	struct hx8369a *ctx = panel_to_hx8369a(panel);
> +	struct drm_display_mode *mode;
> +	const struct drm_display_mode *m = ctx->pd->mode;
> +
> +	mode = drm_mode_duplicate(drm, m);
> +	if (!mode) {
> +		dev_err(drm->dev, "failed to add mode %ux%u@%u\n",
> +			m->hdisplay, m->vdisplay, m->vrefresh);
> +		return 0;
> +	}
> +
> +	drm_mode_set_name(mode);
> +	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> +
> +	connector->display_info.bpc = 8;
> +	connector->display_info.width_mm = mode->width_mm;
> +	connector->display_info.height_mm = mode->height_mm;
> +
> +	drm_mode_probed_add(connector, mode);
> +
> +	return 1;
> +}
> +
> +static const struct drm_panel_funcs hx8369a_dsi_drm_funcs = {
> +	.disable = hx8369a_dsi_disable,
> +	.unprepare = hx8369a_dsi_unprepare,
> +	.prepare = hx8369a_dsi_prepare,
> +	.enable = hx8369a_dsi_enable,
> +	.get_modes = hx8369a_get_modes,
> +};
> +
> +static int hx8369a_power_on(struct hx8369a *ctx)
> +{
> +	int ret;
> +
> +	ret = regulator_bulk_enable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
> +	if (ret < 0)
> +		return ret;
> +
> +	msleep(ctx->pd->power_on_delay);
> +
> +	gpiod_set_value(ctx->reset_gpio, 1);
> +	usleep_range(50, 60);
> +	gpiod_set_value(ctx->reset_gpio, 0);
> +
> +	msleep(ctx->pd->reset_delay);
> +
> +	return 0;
> +}
> +
> +static int hx8369a_power_off(struct hx8369a *ctx)
> +{
> +	return regulator_bulk_disable(ARRAY_SIZE(ctx->supplies), ctx->supplies);;
> +}
> +
> +static int hx8369a_vm_to_res_sel(struct hx8369a *ctx)
> +{
> +	const struct drm_display_mode *mode = ctx->pd->mode;
> +
> +	switch (mode->hdisplay) {
> +	case 480:
> +		switch (mode->vdisplay) {
> +		case 864:
> +			ctx->res_sel = HX8369A_RES_480_864;
> +			break;
> +		case 854:
> +			ctx->res_sel = HX8369A_RES_480_854;
> +			break;
> +		case 800:
> +			ctx->res_sel = HX8369A_RES_480_800;
> +			break;
> +		case 640:
> +			ctx->res_sel = HX8369A_RES_480_640;
> +			break;
> +		case 720:
> +			ctx->res_sel = HX8369A_RES_480_720;
> +			break;
> +		default:
> +			break;
> +		}
> +		break;
> +	case 360:
> +		if (mode->vdisplay == 640)
> +			ctx->res_sel = HX8369A_RES_360_640;
> +		break;
> +	default:
> +		break;
> +	}
> +
> +	return 0;
> +}

Function always returns 0, you can make it void, or return error
in case mode is not supported. As I see the mode is hardcoded in the
driver so the 1st solutions fits here better.

> +
> +static const struct drm_display_mode truly_tft480800_16_e_mode = {
> +	.clock = 26400,
> +	.hdisplay = 480,
> +	.hsync_start = 480 + 8,
> +	.hsync_end = 480 + 8 + 8,
> +	.htotal = 480 + 8 + 8 + 8,
> +	.vdisplay = 800,
> +	.vsync_start = 800 + 6,
> +	.vsync_end = 800 + 6 + 6,
> +	.vtotal = 800 + 6 + 6 + 6,
> +	.vrefresh = 60,
> +	.width_mm = 45,
> +	.height_mm = 76,
> +};
> +
> +static const struct hx8369a_panel_desc truly_tft480800_16_e_dsi = {
> +	.mode = &truly_tft480800_16_e_mode,
> +	.power_on_delay = 10,
> +	.reset_delay = 10,
> +	.dsi_lanes = 2,
> +};
> +
> +static const struct of_device_id hx8369a_dsi_of_match[] = {
> +	{
> +		.compatible = "truly,tft480800-16-e-dsi",
> +		.data = &truly_tft480800_16_e_dsi,
> +	}, {
> +		/* sentinel */
> +	},
> +};
> +MODULE_DEVICE_TABLE(of, hx8369a_dsi_of_match);
> +
> +static int hx8369a_dsi_probe(struct mipi_dsi_device *dsi)
> +{
> +	struct device *dev = &dsi->dev;
> +	const struct of_device_id *of_id =
> +			of_match_device(hx8369a_dsi_of_match, dev);
> +	struct hx8369a *ctx;
> +	int ret, i;
> +	char bs[4];
> +
> +	ctx = devm_kzalloc(dev, sizeof(*ctx), GFP_KERNEL);
> +	if (!ctx)
> +		return -ENOMEM;
> +
> +	ctx->dev = dev;
> +
> +	if (of_id) {
> +		ctx->pd = of_id->data;
> +	} else {
> +		dev_err(dev, "cannot find compatible device\n");
> +		return -ENODEV;
> +	}
> +
> +	ret = hx8369a_vm_to_res_sel(ctx);
> +	if (ret < 0)
> +		return ret;

We know it will always succeed, don't we?

> +
> +	ctx->supplies[0].supply = "vdd1";
> +	ctx->supplies[1].supply = "vdd2";
> +	ctx->supplies[2].supply = "vdd3";
> +	ctx->supplies[3].supply = "dsi-vcc";
> +	ctx->supplies[4].supply = "vpp";
> +	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
> +				      ctx->supplies);
> +	if (ret < 0) {
> +		dev_err(dev, "failed to get regulators: %d\n", ret);

Just nitpicking, here and later, in case of deferred probing you will
have error logged, but it should be at most dev_info.

> +		return ret;
> +	}
> +
> +	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_LOW);
> +	if (IS_ERR(ctx->reset_gpio)) {
> +		dev_err(dev, "cannot get reset-gpios %ld\n",
> +			PTR_ERR(ctx->reset_gpio));
> +		return PTR_ERR(ctx->reset_gpio);
> +	}
> +
> +	for (i = 0; i < 4; i++) {
> +		snprintf(bs, sizeof(bs), "bs%d", i);
> +		ctx->bs_gpio[i] = devm_gpiod_get(dev, bs, GPIOD_OUT_HIGH);
> +
> +		dev_dbg(dev, "bs%d-gpio is configured\n", i);
> +	}
> +
> +	ret = hx8369a_power_on(ctx);
> +	if (ret < 0) {
> +		dev_err(dev, "cannot power on\n");
> +		return ret;
> +	}
> +
> +	drm_panel_init(&ctx->panel);
> +	ctx->panel.dev = dev;
> +	ctx->panel.funcs = &hx8369a_dsi_drm_funcs;
> +
> +	ret = drm_panel_add(&ctx->panel);
> +	if (ret < 0)
> +		return ret;
> +
> +	mipi_dsi_set_drvdata(dsi, ctx);
> +
> +	dsi->channel = 0;
> +	dsi->lanes = ctx->pd->dsi_lanes;
> +	dsi->format = MIPI_DSI_FMT_RGB888;
> +	dsi->mode_flags = MIPI_DSI_MODE_VIDEO |
> +			  MIPI_DSI_MODE_VIDEO_BURST |
> +			  MIPI_DSI_MODE_VIDEO_SYNC_PULSE;
> +	ret = mipi_dsi_attach(dsi);
> +	if (ret < 0)
> +		drm_panel_remove(&ctx->panel);
> +
> +	return ret;
> +}
> +
> +static int hx8369a_dsi_remove(struct mipi_dsi_device *dsi)
> +{
> +	struct hx8369a *ctx = mipi_dsi_get_drvdata(dsi);
> +
> +	mipi_dsi_detach(dsi);
> +	drm_panel_remove(&ctx->panel);
> +	return hx8369a_power_off(ctx);

The sequence here is OK, but as I lurked into dsi host code[1]
it seems dsi host lacks synchronization with drm in
dw_mipi_dsi_host_detach before removing the panel, but it should
be fixed in the host controller.

[1]: [PATCH RFC v4 12/21] drm/bridge: Add Synopsys DesignWare MIPI DSI
host controller driver


Regards
Andrzej


> +}
> +
> +static struct mipi_dsi_driver hx8369a_dsi_driver = {
> +	.probe = hx8369a_dsi_probe,
> +	.remove = hx8369a_dsi_remove,
> +	.driver = {
> +		.name = "panel-hx8369a-dsi",
> +		.of_match_table = hx8369a_dsi_of_match,
> +	},
> +};
> +module_mipi_dsi_driver(hx8369a_dsi_driver);
> +
> +MODULE_DESCRIPTION("Himax HX8369A panel driver");
> +MODULE_AUTHOR("Liu Ying <Ying.Liu@...escale.com>");
> +MODULE_LICENSE("GPL v2");
> 

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