Re: [PATCH 2/3] drm/panel: Add support for the Leadtek LTK08QV25BYL panel

Neil Armstrong
2025-10-29T20:45:27Z

On 10/21/25 09:34, Herve Codina wrote:
> The Leadtek LTK08QV25BYL is a 2.8" 240x320 DSI display.
>
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>
> ---
> drivers/gpu/drm/panel/Kconfig | 12 +
> drivers/gpu/drm/panel/Makefile | 1 +
> .../drm/panel/panel-leadtek-ltk028qv25byl.c | 304 ++++++++++++++++++
> 3 files changed, 317 insertions(+)
> create mode 100644 drivers/gpu/drm/panel/panel-leadtek-ltk028qv25byl.c
>
> diff --git a/drivers/gpu/drm/panel/Kconfig b/drivers/gpu/drm/panel/Kconfig
> index 407c5f6a268b..faa417195b6e 100644
> --- a/drivers/gpu/drm/panel/Kconfig
> +++ b/drivers/gpu/drm/panel/Kconfig
> @@ -367,6 +367,18 @@ config DRM_PANEL_KINGDISPLAY_KD097D04
> 24 bit RGB per pixel. It provides a MIPI DSI interface to
> the host and has a built-in LED backlight.
>
> +config DRM_PANEL_LEADTEK_LTK028QV25BYL
> + tristate "Leadtek LTK028QV25BYL panel"
> + depends on OF
> + depends on DRM_MIPI_DSI
> + depends on BACKLIGHT_CLASS_DEVICE
> + help
> + Say Y here if you want to enable support for Leadtek LTK028QV25BYL
> + TFT-LCD modules. The panel has a 240x320 resolution and uses
> + 18 bit RGB per pixel. It provides a MIPI DSI interface to
> + the host and has a built-in LED backlight.
> +
> +
> config DRM_PANEL_LEADTEK_LTK050H3146W
> tristate "Leadtek LTK050H3146W panel"
> depends on OF
> diff --git a/drivers/gpu/drm/panel/Makefile b/drivers/gpu/drm/panel/Makefile
> index 3615a761b44f..12073c34e0f5 100644
> --- a/drivers/gpu/drm/panel/Makefile
> +++ b/drivers/gpu/drm/panel/Makefile
> @@ -37,6 +37,7 @@ obj-$(CONFIG_DRM_PANEL_JDI_LPM102A188A) += panel-jdi-lpm102a188a.o
> obj-$(CONFIG_DRM_PANEL_JDI_R63452) += panel-jdi-fhd-r63452.o
> obj-$(CONFIG_DRM_PANEL_KHADAS_TS050) += panel-khadas-ts050.o
> obj-$(CONFIG_DRM_PANEL_KINGDISPLAY_KD097D04) += panel-kingdisplay-kd097d04.o
> +obj-$(CONFIG_DRM_PANEL_LEADTEK_LTK028QV25BYL) += panel-leadtek-ltk028qv25byl.o
> obj-$(CONFIG_DRM_PANEL_LEADTEK_LTK050H3146W) += panel-leadtek-ltk050h3146w.o
> obj-$(CONFIG_DRM_PANEL_LEADTEK_LTK500HD1829) += panel-leadtek-ltk500hd1829.o
> obj-$(CONFIG_DRM_PANEL_LINCOLNTECH_LCD197) += panel-lincolntech-lcd197.o
> diff --git a/drivers/gpu/drm/panel/panel-leadtek-ltk028qv25byl.c b/drivers/gpu/drm/panel/panel-leadtek-ltk028qv25byl.c
> new file mode 100644
> index 000000000000..2e3482b2b95c
> --- /dev/null
> +++ b/drivers/gpu/drm/panel/panel-leadtek-ltk028qv25byl.c
> @@ -0,0 +1,304 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Leadtek LTK08QV25BYL 2.8" MIPI-DSI panel driver
> + * Copyright (c) 2025, Bootlin
> + *
> + * base on panel-leadtek-ltk050h346w.c
> + * Copyright (C) 2020 Theobroma Systems Design und Consulting GmbH
> + */
> +
> +#include <linux/delay.h>
> +#include <linux/gpio/consumer.h>
> +#include <linux/mod_devicetable.h>
> +#include <linux/module.h>
> +#include <linux/regulator/consumer.h>
> +
> +#include <video/mipi_display.h>
> +
> +#include <drm/drm_mipi_dsi.h>
> +#include <drm/drm_modes.h>
> +#include <drm/drm_panel.h>
> +
> +struct ltk028qv25byl {
> + struct device *dev;
> + struct drm_panel panel;
> + struct gpio_desc *reset_gpio;
> + struct regulator *vci;
> + struct regulator *iovcc;
> +};
> +
> +static inline struct ltk028qv25byl *panel_to_ltk028qv25byl(struct drm_panel *panel)
> +{
> + return container_of(panel, struct ltk028qv25byl, panel);
> +}
> +
> +static int ltk028qv25byl_init_sequence(struct ltk028qv25byl *ctx)
> +{
> + struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> + struct mipi_dsi_multi_context dsi_ctx = { .dsi = dsi };
> +
> + /*
> + * Init sequence was supplied by the panel vendor. All documentation
> + * provided by the vendor (i.e comments in the provided init sequence)
> + * is also given here as comments without modification.
> + */
> +
> + /* Password */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xdf, 0x98, 0x51, 0xe9);
> +
> + /* Page 0 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xde, 0x00);
> +
> + /* VGMP, VGSP, VGMN, VGSN 4.3 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb7, 0x1e, 0x85, 0x1e, 0x33);
> +
> + /* Set_R_GAMMA */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc8, 0x3f, 0x2e, 0x25, 0x21, 0x23,
> + 0x25, 0x1f, 0x1e, 0x1c, 0x1b, 0x19, 0x11,
> + 0x0e, 0x0a, 0x06, 0x0e, 0x3f, 0x2e, 0x26,
> + 0x21, 0x24, 0x25, 0x1f, 0x1f, 0x1d, 0x1c,
> + 0x19, 0x11, 0x0e, 0x0a, 0x06, 0x0e);
> +
> + /* POW_CTRL */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb9, 0x33, 0x08, 0xcc);
> +
> + /* DCDC_SEL */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xbb, 0x44, 0x7a, 0x30, 0x40, 0x7c,
> + 0x60, 0x70, 0x70);
> +
> + /* VDD_CTRL */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xbc, 0x38, 0x3c);
> +
> + /* SETSTBA */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc0, 0x31, 0x20);
> +
> + /* SETPANEL(default) */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc1, 0x12);
> +
> + /* SETRGBCYC */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc3, 0x08, 0x00, 0x0a, 0x10, 0x08,
> + 0x54, 0x45, 0x71, 0x2c);
> +
> + /* SETRGBCYC(default) */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc4, 0x00, 0xa0, 0x79, 0x0e, 0x0a,
> + 0x16, 0x79, 0x0e, 0x0a, 0x16, 0x79, 0x0e,
> + 0x0a, 0x16, 0x82, 0x00, 0x03);
> +
> + /* SET_GD(default) */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xd0, 0x04, 0x0c, 0x6a, 0x0f, 0x00, 0x03);
> +
> + /* RAMCTRL(default) */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xd7, 0x13, 0x00);
> +
> + /* Page 2 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xde, 0x02);
> +
> + /* DCDC_SET */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xb8, 0x1d, 0xa0, 0x2f, 0x2c, 0x2b);
> +
> + /* SETRGBCYC2 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc1, 0x10, 0x66, 0x66, 0x01);
> +
> + /* Page 0 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xde, 0x00);
> +
> + /* SLPOUT + 120ms delay */
> + mipi_dsi_dcs_exit_sleep_mode_multi(&dsi_ctx);
> + mipi_dsi_msleep(&dsi_ctx, 120);
> +
> + /* Page 2 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xde, 0x02);
> +
> + /* OSCM */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xc5, 0x4e, 0x00, 0x00);
> +
> + /* SETMIPI_2 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xca, 0x30, 0x20, 0xf4);
> +
> + /* Page 4 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xde, 0x04);
> +
> + /* SETPHY3 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xd3, 0x3c);
> +
> + /* Page 0 */
> + mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xde, 0x00);
> +
> + /* Display on + 20ms delay */
> + mipi_dsi_dcs_set_display_on_multi(&dsi_ctx);
> + mipi_dsi_msleep(&dsi_ctx, 20);
> +
> + return dsi_ctx.accum_err;
> +}
> +
> +static int ltk028qv25byl_unprepare(struct drm_panel *panel)
> +{
> + struct ltk028qv25byl *ctx = panel_to_ltk028qv25byl(panel);
> + struct mipi_dsi_device *dsi = to_mipi_dsi_device(ctx->dev);
> + struct mipi_dsi_multi_context dsi_ctx = { .dsi = dsi };
> +
> + mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
> + mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);
> + if (dsi_ctx.accum_err)
> + return dsi_ctx.accum_err;
> +
> + gpiod_set_value_cansleep(ctx->reset_gpio, 1);
> +
> + regulator_disable(ctx->iovcc);
> + regulator_disable(ctx->vci);
> +
> + return 0;
> +}
> +
> +static int ltk028qv25byl_prepare(struct drm_panel *panel)
> +{
> + struct ltk028qv25byl *ctx = panel_to_ltk028qv25byl(panel);
> + int ret;
> +
> + ret = regulator_enable(ctx->vci);
> + if (ret < 0) {
> + dev_err(ctx->dev, "Failed to enable vcc supply (%d)\n", ret);
> + return ret;
> + }
> + ret = regulator_enable(ctx->iovcc);
> + if (ret < 0) {
> + dev_err(ctx->dev, "Failed to enable iovcc supply (%d)\n", ret);
> + goto disable_vci;
> + }
> +
> + gpiod_set_value_cansleep(ctx->reset_gpio, 1);
> + usleep_range(5000, 6000);
> + gpiod_set_value_cansleep(ctx->reset_gpio, 0);
> + msleep(20);
> +
> + ret = ltk028qv25byl_init_sequence(ctx);
> + if (ret)
> + goto force_reset;
> +
> + return 0;
> +
> +force_reset:
> + gpiod_set_value_cansleep(ctx->reset_gpio, 1);
> + regulator_disable(ctx->iovcc);
> +disable_vci:
> + regulator_disable(ctx->vci);
> + return ret;
> +}
> +
> +static const struct drm_display_mode ltk028qv25byl_mode = {
> + .hdisplay = 240,
> + .hsync_start = 240 + 120,
> + .hsync_end = 240 + 120 + 4,
> + .htotal = 240 + 120 + 4 + 120,
> + .vdisplay = 320,
> + .vsync_start = 320 + 8,
> + .vsync_end = 320 + 8 + 2,
> + .vtotal = 320 + 8 + 2 + 6,
> + .clock = 10000000 / 1000,

Usually we calculate the clock from the mode parameters, won't it work here ?

> + .flags = DRM_MODE_FLAG_NVSYNC | DRM_MODE_FLAG_NHSYNC,
> + .width_mm = 45,
> + .height_mm = 62,
> +};
> +
> +static int ltk028qv25byl_get_modes(struct drm_panel *panel,
> + struct drm_connector *connector)
> +{
> + struct drm_display_mode *mode;
> +
> + mode = drm_mode_duplicate(connector->dev, &ltk028qv25byl_mode);
> + if (!mode)
> + return -ENOMEM;
> +
> + drm_mode_set_name(mode);
> +
> + mode->type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED;
> + 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 ltk028qv25byl_funcs = {
> + .unprepare = ltk028qv25byl_unprepare,
> + .prepare = ltk028qv25byl_prepare,
> + .get_modes = ltk028qv25byl_get_modes,
> +};
> +
> +static int ltk028qv25byl_probe(struct mipi_dsi_device *dsi)
> +{
> + struct device *dev = &dsi->dev;
> + struct ltk028qv25byl *ctx;
> + int ret;
> +
> + ctx = devm_drm_panel_alloc(dev, __typeof(*ctx), panel,
> + &ltk028qv25byl_funcs,
> + DRM_MODE_CONNECTOR_DSI);
> + if (IS_ERR(ctx))
> + return PTR_ERR(ctx);
> +
> + ctx->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_LOW);
> + if (IS_ERR(ctx->reset_gpio))
> + return dev_err_probe(dev, PTR_ERR(ctx->reset_gpio),
> + "Failed to get reset gpio\n");
> +
> + ctx->vci = devm_regulator_get(dev, "vci");
> + if (IS_ERR(ctx->vci))
> + return dev_err_probe(dev, PTR_ERR(ctx->vci),
> + "Failed to get vcc regulator\n");
> +
> + ctx->iovcc = devm_regulator_get(dev, "iovcc");
> + if (IS_ERR(ctx->iovcc))
> + return dev_err_probe(dev, PTR_ERR(ctx->iovcc),
> + "Failed to get iovcc regulator\n");

Can you switch to devm_regulator_bulk_get_const() ?

> +
> + mipi_dsi_set_drvdata(dsi, ctx);
> +
> + ctx->dev = dev;
> +
> + dsi->lanes = 1;
> + dsi->format = MIPI_DSI_FMT_RGB888;
> + dsi->mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_VIDEO_BURST |
> + MIPI_DSI_MODE_LPM | MIPI_DSI_MODE_NO_EOT_PACKET;
> +
> + ret = drm_panel_of_backlight(&ctx->panel);
> + if (ret)
> + return ret;
> +
> + drm_panel_add(&ctx->panel);
> +
> + ret = devm_mipi_dsi_attach(dev, dsi);
> + if (ret < 0) {
> + drm_panel_remove(&ctx->panel);
> + return dev_err_probe(dev, ret, "Failed to attach to DSI host\n");
> + }
> +
> + return 0;
> +}
> +
> +static void ltk028qv25byl_remove(struct mipi_dsi_device *dsi)
> +{
> + struct ltk028qv25byl *ctx = mipi_dsi_get_drvdata(dsi);
> +
> + drm_panel_remove(&ctx->panel);
> +}
> +
> +static const struct of_device_id ltk028qv25byl_of_match[] = {
> + { .compatible = "leadtek,ltk028qv25byl" },
> + { /* sentinel */ }
> +};
> +MODULE_DEVICE_TABLE(of, ltk028qv25byl_of_match);
> +
> +static struct mipi_dsi_driver ltk028qv25byl_driver = {
> + .driver = {
> + .name = "panel-leadtek-ltk028qv25byl",
> + .of_match_table = ltk028qv25byl_of_match,
> + },
> + .probe = ltk028qv25byl_probe,
> + .remove = ltk028qv25byl_remove,
> +};
> +module_mipi_dsi_driver(ltk028qv25byl_driver);
> +
> +MODULE_AUTHOR("Herve Codina <herve.codina@bootlin.com>");
> +MODULE_DESCRIPTION("DRM driver for Leadtek LTK028QV25BYL MIPI DSI panel");
> +MODULE_LICENSE("GPL");

Thanks,
Neil