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Subject: Re: [PATCH v3 2/2] drm/panel: Add driver for Samsung S6E63M0 panel
To:     =?UTF-8?Q?Pawe=c5=82_Chmiel?= <pawel.mikolaj.chmiel@gmail.com>,
        thierry.reding@gmail.com
Cc:     mark.rutland@arm.com, devicetree@vger.kernel.org, airlied@linux.ie,
        linux-kernel@vger.kernel.org, krzk@kernel.org, robh+dt@kernel.org,
        dri-devel@lists.freedesktop.org, m.szyprowski@samsung.com
From:   Andrzej Hajda <a.hajda@samsung.com>
Message-ID: <82ccf31e-13c3-1cd5-d87a-0c3291eb0224@samsung.com>
Date:   Mon, 11 Feb 2019 16:35:19 +0100
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        <20190202142748.6830-2-pawel.mikolaj.chmiel@gmail.com>
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On 02.02.2019 15:27, Paweł Chmiel wrote:
> This patch adds Samsung S6E63M0 AMOLED LCD panel driver, connected over
> spi. It's based on already removed, non dt s6e63m0 driver and
> panel-samsung-ld9040. It can be found for example in some of Samsung
> Aries based phones.
>
> Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
> Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
> ---
> Changes from v2:
>   - VIDEOMODE_HELPERS is not needed in Kconfig
>   - Added help text to Kconfig
>   - Remove unneeded videomode includes/fields
>   - Add sentinel comment in s6e63m0_of_match struct
>   - Handle errors during registration of backlight device. We shouldn't
>     register panel if we fail to register backlight device
>   - Added Reviewed-by
>
> Changes from v1:
>   - Correct order of Kconfig/Makefile entry
>   - Fix SPDX tag, so it matches value of MODULE_LICENSE
>   - Remove inclusion of drmP.h
>   - Fix code formatting
>   - Use DRM_DEV_ERROR/DEBUG
>   - Extract hardcoded values
>   - Remove possibility to change gamma through sysfs, leaving only one
>     gamma table values
>   - Fix reset_gpio handling, so it'll be asserted in power_on and
>     deasserted in power_off. Also do it before turning voltage on.
>   - Disable backlight and enter sleep mode in disable callback.
>     Previously it was done in unprepare
>   - Enable display and backlight in enable callback. Previously it was
>     done in prepare
>   - Hardcode display timings and delays. Previously they were readed
>     from device tree
>   - We're using SPDX, so we don't need to have license body
>   - Use MIPI_DCS_EXIT_SLEEP_MODE and MIPI_DCS_SET_DISPLAY_ON
>   - Rename MAX_GAMMA_LEVEL to NUM_GAMMA_LEVELS
>   - Ommit get_brightness callback
>   - Use backlight_enable/disable API, like it's done in other panel
>     drivers (for example panel-simple)
>   - Make set_brightness called only from backlight api, like it's done
>     in other panel drivers (for example panel-simple).
>   - Reset gpio should be set to GPIOD_OUT_HIGH. It's declared as active
>     low in device tree
>   - Don't call power_off in remove callback
> ---
>  drivers/gpu/drm/panel/Kconfig                 |   9 +
>  drivers/gpu/drm/panel/Makefile                |   1 +
>  drivers/gpu/drm/panel/panel-samsung-s6e63m0.c | 517 ++++++++++++++++++
>  3 files changed, 527 insertions(+)
>  create mode 100644 drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 3f3537719beb..45e9ab4b7857 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -158,6 +158,15 @@ config DRM_PANEL_SAMSUNG_S6E63J0X03
>  	depends on BACKLIGHT_CLASS_DEVICE
>  	select VIDEOMODE_HELPERS
>  
> +config DRM_PANEL_SAMSUNG_S6E63M0
> +	tristate "Samsung S6E63M0 RGB/SPI panel"
> +	depends on OF
> +	depends on SPI
> +	depends on BACKLIGHT_CLASS_DEVICE
> +	help
> +	  Say Y here if you want to enable support for Samsung s6e63m0
> +	  AMOLED LCD panel.
> +
>  config DRM_PANEL_SAMSUNG_S6E8AA0
>  	tristate "Samsung S6E8AA0 DSI video mode panel"
>  	depends on OF
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index 4396658a7996..4507a2d253ac 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -16,6 +16,7 @@ obj-$(CONFIG_DRM_PANEL_SAMSUNG_LD9040) += panel-samsung-ld9040.o
>  obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6D16D0) += panel-samsung-s6d16d0.o
>  obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6E3HA2) += panel-samsung-s6e3ha2.o
>  obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6E63J0X03) += panel-samsung-s6e63j0x03.o
> +obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6E63M0) += panel-samsung-s6e63m0.o
>  obj-$(CONFIG_DRM_PANEL_SAMSUNG_S6E8AA0) += panel-samsung-s6e8aa0.o
>  obj-$(CONFIG_DRM_PANEL_SEIKO_43WVF1G) += panel-seiko-43wvf1g.o
>  obj-$(CONFIG_DRM_PANEL_SHARP_LQ101R1SX01) += panel-sharp-lq101r1sx01.o
> diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c b/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
> new file mode 100644
> index 000000000000..4312aa3e4386
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0.c
> @@ -0,0 +1,517 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * S6E63M0 AMOLED LCD drm_panel driver.
> + *
> + * Copyright (C) 2019 Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
> + * Derived from drivers/gpu/drm/panel-samsung-ld9040.c
> + *
> + * Andrzej Hajda <a.hajda@samsung.com>
> + */
> +
> +#include <drm/drm_modes.h>
> +#include <drm/drm_panel.h>
> +#include <drm/drm_print.h>
> +
> +#include <linux/backlight.h>
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/spi/spi.h>
> +
> +#include <video/mipi_display.h>
> +
> +/* Manufacturer Command Set */
> +#define MCS_ELVSS_ON                0xb1
> +#define MCS_ACL_CTRL                0xc0
> +#define MCS_DISPLAY_CONDITION   0xf2
> +#define MCS_ETC_CONDITION           0xf6
> +#define MCS_PANEL_CONDITION         0xF8
> +#define MCS_GAMMA_CTRL              0xfa
> +
> +#define NUM_GAMMA_LEVELS             11
> +#define GAMMA_TABLE_COUNT           23
> +
> +#define DATA_MASK                                       0x100
> +
> +#define MAX_BRIGHTNESS              (NUM_GAMMA_LEVELS - 1)
> +
> +/* array of gamma tables for gamma value 2.2 */
> +static u8 const s6e63m0_gamma_22[NUM_GAMMA_LEVELS][GAMMA_TABLE_COUNT] = {
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x78, 0xEC, 0x3D, 0xC8,
> +	  0xC2, 0xB6, 0xC4, 0xC7, 0xB6, 0xD5, 0xD7,
> +	  0xCC, 0x00, 0x39, 0x00, 0x36, 0x00, 0x51 },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x73, 0x4A, 0x3D, 0xC0,
> +	  0xC2, 0xB1, 0xBB, 0xBE, 0xAC, 0xCE, 0xCF,
> +	  0xC5, 0x00, 0x5D, 0x00, 0x5E, 0x00, 0x82 },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x70, 0x51, 0x3E, 0xBF,
> +	  0xC1, 0xAF, 0xB9, 0xBC, 0xAB, 0xCC, 0xCC,
> +	  0xC2, 0x00, 0x65, 0x00, 0x67, 0x00, 0x8D },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x6C, 0x54, 0x3A, 0xBC,
> +	  0xBF, 0xAC, 0xB7, 0xBB, 0xA9, 0xC9, 0xC9,
> +	  0xBE, 0x00, 0x71, 0x00, 0x73, 0x00, 0x9E },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x69, 0x54, 0x37, 0xBB,
> +	  0xBE, 0xAC, 0xB4, 0xB7, 0xA6, 0xC7, 0xC8,
> +	  0xBC, 0x00, 0x7B, 0x00, 0x7E, 0x00, 0xAB },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x66, 0x55, 0x34, 0xBA,
> +	  0xBD, 0xAB, 0xB1, 0xB5, 0xA3, 0xC5, 0xC6,
> +	  0xB9, 0x00, 0x85, 0x00, 0x88, 0x00, 0xBA },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x63, 0x53, 0x31, 0xB8,
> +	  0xBC, 0xA9, 0xB0, 0xB5, 0xA2, 0xC4, 0xC4,
> +	  0xB8, 0x00, 0x8B, 0x00, 0x8E, 0x00, 0xC2 },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x62, 0x54, 0x30, 0xB9,
> +	  0xBB, 0xA9, 0xB0, 0xB3, 0xA1, 0xC1, 0xC3,
> +	  0xB7, 0x00, 0x91, 0x00, 0x95, 0x00, 0xDA },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x66, 0x58, 0x34, 0xB6,
> +	  0xBA, 0xA7, 0xAF, 0xB3, 0xA0, 0xC1, 0xC2,
> +	  0xB7, 0x00, 0x97, 0x00, 0x9A, 0x00, 0xD1 },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x64, 0x56, 0x33, 0xB6,
> +	  0xBA, 0xA8, 0xAC, 0xB1, 0x9D, 0xC1, 0xC1,
> +	  0xB7, 0x00, 0x9C, 0x00, 0x9F, 0x00, 0xD6 },
> +	{ MCS_GAMMA_CTRL, 0x00,
> +	  0x18, 0x08, 0x24, 0x5f, 0x50, 0x2d, 0xB6,
> +	  0xB9, 0xA7, 0xAd, 0xB1, 0x9f, 0xbe, 0xC0,
> +	  0xB5, 0x00, 0xa0, 0x00, 0xa4, 0x00, 0xdb },
> +};
> +
> +struct s6e63m0 {
> +	struct device *dev;
> +	struct drm_panel panel;
> +	struct backlight_device *bl_dev;
> +
> +	struct regulator_bulk_data supplies[2];
> +	struct gpio_desc *reset_gpio;
> +
> +	bool prepared;
> +	bool enabled;
> +
> +	/*
> +	 * This field is tested by functions directly accessing bus before
> +	 * transfer, transfer is skipped if it is set. In case of transfer
> +	 * failure or unexpected response the field is set to error value.
> +	 * Such construct allows to eliminate many checks in higher level
> +	 * functions.
> +	 */
> +	int error;
> +};
> +
> +static const struct drm_display_mode default_mode = {
> +	.clock		= 25628,
> +	.hdisplay	= 480,
> +	.hsync_start	= 480 + 16,
> +	.hsync_end	= 480 + 16 + 2,
> +	.htotal		= 480 + 16 + 2 + 16,
> +	.vdisplay	= 800,
> +	.vsync_start	= 800 + 28,
> +	.vsync_end	= 800 + 28 + 2,
> +	.vtotal		= 800 + 28 + 2 + 1,
> +	.vrefresh	= 60,
> +	.width_mm	= 53,
> +	.height_mm	= 89,
> +	.flags		= DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> +};
> +
> +static inline struct s6e63m0 *panel_to_s6e63m0(struct drm_panel *panel)
> +{
> +	return container_of(panel, struct s6e63m0, panel);
> +}
> +
> +static int s6e63m0_clear_error(struct s6e63m0 *ctx)
> +{
> +	int ret = ctx->error;
> +
> +	ctx->error = 0;
> +	return ret;
> +}
> +
> +static int s6e63m0_spi_write_word(struct s6e63m0 *ctx, u16 data)
> +{
> +	struct spi_device *spi = to_spi_device(ctx->dev);
> +	struct spi_transfer xfer = {
> +		.len	= 2,
> +		.tx_buf = &data,
> +	};
> +	struct spi_message msg;
> +
> +	spi_message_init(&msg);
> +	spi_message_add_tail(&xfer, &msg);
> +
> +	return spi_sync(spi, &msg);
> +}
> +
> +static void s6e63m0_dcs_write(struct s6e63m0 *ctx, const u8 *data, size_t len)
> +{
> +	int ret = 0;
> +
> +	if (ctx->error < 0 || len == 0)
> +		return;
> +
> +	DRM_DEV_DEBUG(ctx->dev, "writing dcs seq: %*ph\n", (int)len, data);
> +	ret = s6e63m0_spi_write_word(ctx, *data);
> +
> +	while (!ret && --len) {
> +		++data;
> +		ret = s6e63m0_spi_write_word(ctx, *data | DATA_MASK);
> +	}
> +
> +	if (ret) {
> +		DRM_DEV_ERROR(ctx->dev, "error %d writing dcs seq: %*ph\n", ret,
> +			      (int)len, data);
> +		ctx->error = ret;
> +	}
> +
> +	usleep_range(300, 310);
> +}
> +
> +#define s6e63m0_dcs_write_seq_static(ctx, seq ...) \
> +	({ \
> +		static const u8 d[] = { seq }; \
> +		s6e63m0_dcs_write(ctx, d, ARRAY_SIZE(d)); \
> +	})
> +
> +static void s6e63m0_brightness_set(struct s6e63m0 *ctx)
> +{
> +	int brightness = ctx->bl_dev->props.brightness;
> +
> +	/* disable and set new gamma */
> +	s6e63m0_dcs_write(ctx, s6e63m0_gamma_22[brightness],
> +			  ARRAY_SIZE(s6e63m0_gamma_22[brightness]));
> +
> +	/* update gamma table. */
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_GAMMA_CTRL, 0x01);
> +}


I guess you can squash this callback into s6e63m0_set_brightness.
Moreover you performs transfer here unconditionally, regardless of panel
power state, it will fail when drm device is disabled (using echo 255
>/sys/class/backlight/...) - panel is also disabled - making transfer to
disabled panel by panel driver looks odd, moreover it could be little
bit racy. But in practice it could work.

Moreover I do not see usage of backlight_properties.power,
backlight_properties.state, but I do not understand how exactly
backlight interface should work, if someone can point out to proper
docs/usage of backlight API I will be glad.


> +
> +static void s6e63m0_init(struct s6e63m0 *ctx)
> +{
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_PANEL_CONDITION,
> +				     0x01, 0x27, 0x27, 0x07, 0x07, 0x54, 0x9f,
> +				     0x63, 0x86, 0x1a, 0x33, 0x0d, 0x00, 0x00);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_DISPLAY_CONDITION,
> +				     0x02, 0x03, 0x1c, 0x10, 0x10);
> +	s6e63m0_dcs_write_seq_static(ctx, 0xf7,
> +				     0x03, 0x00, 0x00);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_GAMMA_CTRL,
> +				     0x00, 0x18, 0x08, 0x24, 0x64, 0x56, 0x33,
> +				     0xb6, 0xba, 0xa8, 0xac, 0xb1, 0x9d, 0xc1,
> +				     0xc1, 0xb7, 0x00, 0x9c, 0x00, 0x9f, 0x00,
> +				     0xd6);
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_GAMMA_CTRL,
> +				     0x01);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_ETC_CONDITION,
> +				     0x00, 0x8c, 0x07);
> +	s6e63m0_dcs_write_seq_static(ctx, 0xb3,
> +				     0xc);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xb5,
> +				     0x2c, 0x12, 0x0c, 0x0a, 0x10, 0x0e, 0x17,
> +				     0x13, 0x1f, 0x1a, 0x2a, 0x24, 0x1f, 0x1b,
> +				     0x1a, 0x17, 0x2b, 0x26, 0x22, 0x20, 0x3a,
> +				     0x34, 0x30, 0x2c, 0x29, 0x26, 0x25, 0x23,
> +				     0x21, 0x20, 0x1e, 0x1e);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xb6,
> +				     0x00, 0x00, 0x11, 0x22, 0x33, 0x44, 0x44,
> +				     0x44, 0x55, 0x55, 0x66, 0x66, 0x66, 0x66,
> +				     0x66, 0x66);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xb7,
> +				     0x2c, 0x12, 0x0c, 0x0a, 0x10, 0x0e, 0x17,
> +				     0x13, 0x1f, 0x1a, 0x2a, 0x24, 0x1f, 0x1b,
> +				     0x1a, 0x17, 0x2b, 0x26, 0x22, 0x20, 0x3a,
> +				     0x34, 0x30, 0x2c, 0x29, 0x26, 0x25, 0x23,
> +				     0x21, 0x20, 0x1e, 0x1e, 0x00, 0x00, 0x11,
> +				     0x22, 0x33, 0x44, 0x44, 0x44, 0x55, 0x55,
> +				     0x66, 0x66, 0x66, 0x66, 0x66, 0x66);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xb9,
> +				     0x2c, 0x12, 0x0c, 0x0a, 0x10, 0x0e, 0x17,
> +				     0x13, 0x1f, 0x1a, 0x2a, 0x24, 0x1f, 0x1b,
> +				     0x1a, 0x17, 0x2b, 0x26, 0x22, 0x20, 0x3a,
> +				     0x34, 0x30, 0x2c, 0x29, 0x26, 0x25, 0x23,
> +				     0x21, 0x20, 0x1e, 0x1e);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xba,
> +				     0x00, 0x00, 0x11, 0x22, 0x33, 0x44, 0x44,
> +				     0x44, 0x55, 0x55, 0x66, 0x66, 0x66, 0x66,
> +				     0x66, 0x66);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xc1,
> +				     0x4d, 0x96, 0x1d, 0x00, 0x00, 0x01, 0xdf,
> +				     0x00, 0x00, 0x03, 0x1f, 0x00, 0x00, 0x00,
> +				     0x00, 0x00, 0x00, 0x00, 0x00, 0x03, 0x06,
> +				     0x09, 0x0d, 0x0f, 0x12, 0x15, 0x18);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, 0xb2,
> +				     0x10, 0x10, 0x0b, 0x05);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_ACL_CTRL,
> +				     0x01);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MCS_ELVSS_ON,
> +				     0x0b);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MIPI_DCS_EXIT_SLEEP_MODE);
> +}
> +
> +static int s6e63m0_power_on(struct s6e63m0 *ctx)
> +{
> +	int ret;
> +
> +	gpiod_set_value(ctx->reset_gpio, 0);
> +	msleep(120);
> +
> +	ret = regulator_bulk_enable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
> +	if (ret < 0)
> +		return ret;


Are you sure gpios before regulators, from my experience usually it is
reverse.


> +
> +	msleep(25);
> +
> +	return 0;
> +}
> +
> +static int s6e63m0_power_off(struct s6e63m0 *ctx)
> +{
> +	int ret;
> +
> +	ret = regulator_bulk_disable(ARRAY_SIZE(ctx->supplies), ctx->supplies);
> +	if (ret < 0)
> +		return ret;
> +
> +	gpiod_set_value(ctx->reset_gpio, 1);


Ditto.


> +	msleep(120);


What is the point of this msleep?


I guess, the answer for above comments can be difficult, since datasheet
is not available, so if you just followed vendor code please feel free
to add:

Reviewed-by: Andrzej Hajda <a.hajda@samsung.com>

--

Regards
Andrzej


> +
> +	return 0;
> +}
> +
> +static int s6e63m0_disable(struct drm_panel *panel)
> +{
> +	struct s6e63m0 *ctx = panel_to_s6e63m0(panel);
> +
> +	if (!ctx->enabled)
> +		return 0;
> +
> +	backlight_disable(ctx->bl_dev);
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MIPI_DCS_ENTER_SLEEP_MODE);
> +	msleep(200);
> +
> +	ctx->enabled = false;
> +
> +	return 0;
> +}
> +
> +static int s6e63m0_unprepare(struct drm_panel *panel)
> +{
> +	struct s6e63m0 *ctx = panel_to_s6e63m0(panel);
> +	int ret;
> +
> +	if (!ctx->prepared)
> +		return 0;
> +
> +	s6e63m0_clear_error(ctx);
> +
> +	ret = s6e63m0_power_off(ctx);
> +	if (ret < 0)
> +		return ret;
> +
> +	ctx->prepared = false;
> +
> +	return 0;
> +}
> +
> +static int s6e63m0_prepare(struct drm_panel *panel)
> +{
> +	struct s6e63m0 *ctx = panel_to_s6e63m0(panel);
> +	int ret;
> +
> +	if (ctx->prepared)
> +		return 0;
> +
> +	ret = s6e63m0_power_on(ctx);
> +	if (ret < 0)
> +		return ret;
> +
> +	s6e63m0_init(ctx);
> +
> +	ret = s6e63m0_clear_error(ctx);
> +
> +	if (ret < 0)
> +		s6e63m0_unprepare(panel);
> +
> +	ctx->prepared = true;
> +
> +	return ret;
> +}
> +
> +static int s6e63m0_enable(struct drm_panel *panel)
> +{
> +	struct s6e63m0 *ctx = panel_to_s6e63m0(panel);
> +
> +	if (ctx->enabled)
> +		return 0;
> +
> +	s6e63m0_dcs_write_seq_static(ctx, MIPI_DCS_SET_DISPLAY_ON);
> +
> +	backlight_enable(ctx->bl_dev);
> +
> +	ctx->enabled = true;
> +
> +	return 0;
> +}
> +
> +static int s6e63m0_get_modes(struct drm_panel *panel)
> +{
> +	struct drm_connector *connector = panel->connector;
> +	struct drm_display_mode *mode;
> +
> +	mode = drm_mode_duplicate(panel->drm, &default_mode);
> +	if (!mode) {
> +		DRM_ERROR("failed to add mode %ux%ux@%u\n",
> +			  default_mode.hdisplay, default_mode.vdisplay,
> +			  default_mode.vrefresh);
> +		return -ENOMEM;
> +	}
> +
> +	drm_mode_set_name(mode);
> +
> +	mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> +	drm_mode_probed_add(connector, mode);
> +
> +	return 1;
> +}
> +
> +static const struct drm_panel_funcs s6e63m0_drm_funcs = {
> +	.disable	= s6e63m0_disable,
> +	.unprepare	= s6e63m0_unprepare,
> +	.prepare	= s6e63m0_prepare,
> +	.enable		= s6e63m0_enable,
> +	.get_modes	= s6e63m0_get_modes,
> +};
> +
> +static int s6e63m0_set_brightness(struct backlight_device *bd)
> +{
> +	struct s6e63m0 *ctx = bl_get_data(bd);
> +
> +	s6e63m0_brightness_set(ctx);
> +
> +	return s6e63m0_clear_error(ctx);
> +}
> +
> +static const struct backlight_ops s6e63m0_backlight_ops = {
> +	.update_status	= s6e63m0_set_brightness,
> +};
> +
> +static int s6e63m0_backlight_register(struct s6e63m0 *ctx)
> +{
> +	struct backlight_properties props = {
> +		.type		= BACKLIGHT_RAW,
> +		.brightness	= MAX_BRIGHTNESS,
> +		.max_brightness = MAX_BRIGHTNESS
> +	};
> +	struct device *dev = ctx->dev;
> +	int ret = 0;
> +
> +	ctx->bl_dev = devm_backlight_device_register(dev, "panel", dev, ctx,
> +						     &s6e63m0_backlight_ops,
> +						     &props);
> +	if (IS_ERR(ctx->bl_dev)) {
> +		ret = PTR_ERR(ctx->bl_dev);
> +		DRM_DEV_ERROR(dev, "error registering backlight device (%d)\n",
> +			      ret);
> +	}
> +
> +	return ret;
> +}
> +
> +static int s6e63m0_probe(struct spi_device *spi)
> +{
> +	struct device *dev = &spi->dev;
> +	struct s6e63m0 *ctx;
> +	int ret;
> +
> +	ctx = devm_kzalloc(dev, sizeof(struct s6e63m0), GFP_KERNEL);
> +	if (!ctx)
> +		return -ENOMEM;
> +
> +	spi_set_drvdata(spi, ctx);
> +
> +	ctx->dev = dev;
> +	ctx->enabled = false;
> +	ctx->prepared = false;
> +
> +	ctx->supplies[0].supply = "vdd3";
> +	ctx->supplies[1].supply = "vci";
> +	ret = devm_regulator_bulk_get(dev, ARRAY_SIZE(ctx->supplies),
> +				      ctx->supplies);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "failed to get regulators: %d\n", ret);
> +		return ret;
> +	}
> +
> +	ctx->reset_gpio = devm_gpiod_get(dev, "reset", GPIOD_OUT_HIGH);
> +	if (IS_ERR(ctx->reset_gpio)) {
> +		DRM_DEV_ERROR(dev, "cannot get reset-gpios %ld\n",
> +			      PTR_ERR(ctx->reset_gpio));
> +		return PTR_ERR(ctx->reset_gpio);
> +	}
> +
> +	spi->bits_per_word = 9;
> +	spi->mode = SPI_MODE_3;
> +	ret = spi_setup(spi);
> +	if (ret < 0) {
> +		DRM_DEV_ERROR(dev, "spi setup failed.\n");
> +		return ret;
> +	}
> +
> +	drm_panel_init(&ctx->panel);
> +	ctx->panel.dev = dev;
> +	ctx->panel.funcs = &s6e63m0_drm_funcs;
> +
> +	ret = s6e63m0_backlight_register(ctx);
> +	if (ret < 0)
> +		return ret;
> +
> +	return drm_panel_add(&ctx->panel);
> +}
> +
> +static int s6e63m0_remove(struct spi_device *spi)
> +{
> +	struct s6e63m0 *ctx = spi_get_drvdata(spi);
> +
> +	drm_panel_remove(&ctx->panel);
> +
> +	return 0;
> +}
> +
> +static const struct of_device_id s6e63m0_of_match[] = {
> +	{ .compatible = "samsung,s6e63m0" },
> +	{ /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, s6e63m0_of_match);
> +
> +static struct spi_driver s6e63m0_driver = {
> +	.probe			= s6e63m0_probe,
> +	.remove			= s6e63m0_remove,
> +	.driver			= {
> +		.name		= "panel-samsung-s6e63m0",
> +		.of_match_table = s6e63m0_of_match,
> +	},
> +};
> +module_spi_driver(s6e63m0_driver);
> +
> +MODULE_AUTHOR("Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>");
> +MODULE_DESCRIPTION("s6e63m0 LCD Driver");
> +MODULE_LICENSE("GPL v2");