Re: [PATCH RFC 04/10] drm/panel: novatek-nt36672a: add Tianma FHD+ video mode panel

["Barnabás Czémán" <barnabas.czeman@mainlining.org>]

On 2026-09-11 10:51, YİĞİTCAN KAVAKLI wrote:
> Add support for the 1080x2340 Tianma video mode panel with Novatek
> NT36672A driver IC found in the Xiaomi Redmi Note 8 (ginkgo / SM6125).
> 
> Changes:
> - Add 1080x2340 display mode timings (183.025 MHz pixel clock)
> - Add verified DCS initialization sequences for pages 0x25, 0x20, 0x24,
>   0x26, and user command page 0x10
> - Add standard DRM panel .enable and .disable callbacks to coordinate
>   display on/off commands with active DSI video stream
> - Set prepare_prev_first = true for host controller synchronization
> - Optimize power-on reset sequence to nominal 10ms timings
> 
> Signed-off-by: YİĞİTCAN KAVAKLI <kavakliyigitcan@gmail.com>
> ---
>  drivers/gpu/drm/panel/panel-novatek-nt36672a.c | 141 
> ++++++++++++++++++++-----
>  1 file changed, 117 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/gpu/drm/panel/panel-novatek-nt36672a.c 
> b/drivers/gpu/drm/panel/panel-novatek-nt36672a.c
> index 
> 464d9ce47d87dc857c3a565a63156ac79ddeb30c..b69213790441f204016895a391b58f676762b1aa 
> 100644
> --- a/drivers/gpu/drm/panel/panel-novatek-nt36672a.c
> +++ b/drivers/gpu/drm/panel/panel-novatek-nt36672a.c
> @@ -34,7 +34,7 @@ static const char * const nt36672a_regulator_names[] 
> = {
>  	"vddneg",
>  };
> 
> -static unsigned long const nt36672a_regulator_enable_loads[] = {
> +static const unsigned long nt36672a_regulator_enable_loads[] = {
>  	62000,
>  	100000,
>  	100000
> @@ -92,18 +92,12 @@ static int nt36672a_panel_unprepare(struct 
> drm_panel *panel)
>  	if (pinfo->desc->send_deinit_cmds)
>  		pinfo->desc->send_deinit_cmds(&dsi_ctx);
> 
> -	/* Reset error to continue with display off even if send_cmds failed 
> */
> +	/* Reset error to continue power-down even if send_cmds failed */
>  	dsi_ctx.accum_err = 0;
> -	mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
> -	/* Reset error to continue power-down even if display off failed */
> -	dsi_ctx.accum_err = 0;
> -
> -	/* 120ms delay required here as per DCS spec */
> -	msleep(120);
> 
>  	mipi_dsi_dcs_enter_sleep_mode_multi(&dsi_ctx);
> 
> -	/* 0x3C = 60ms delay */
> +	/* 60ms delay as per DCS spec */
>  	msleep(60);
> 
>  	nt36672a_panel_power_off(panel);
> @@ -120,15 +114,14 @@ static int nt36672a_panel_power_on(struct 
> nt36672a_panel *pinfo)
>  		return ret;
> 
>  	/*
> -	 * As per downstream kernel, Reset sequence of Tianma FHD panel 
> requires the panel to
> -	 * be out of reset for 10ms, followed by being held in reset for 
> 10ms. But for Android
> -	 * AOSP, we needed to bump it upto 200ms otherwise we get white 
> screen sometimes.
> -	 * FIXME: Try to reduce this 200ms to a lesser value.
> +	 * Reset sequence: 10ms out of reset, 10ms held in reset, 10ms out of 
> reset.
>  	 */
> -	gpiod_set_value(pinfo->reset_gpio, 1);
> -	msleep(200);
> -	gpiod_set_value(pinfo->reset_gpio, 0);
> -	msleep(200);
> +	gpiod_set_value_cansleep(pinfo->reset_gpio, 0);
> +	usleep_range(10000, 11000);
> +	gpiod_set_value_cansleep(pinfo->reset_gpio, 1);
> +	usleep_range(10000, 11000);
> +	gpiod_set_value_cansleep(pinfo->reset_gpio, 0);
> +	usleep_range(10000, 11000);
> 
>  	return 0;
>  }
> @@ -146,19 +139,41 @@ static int nt36672a_panel_prepare(struct 
> drm_panel *panel)
> 
>  	mipi_dsi_dcs_exit_sleep_mode_multi(&dsi_ctx);
> 
> -	/* 0x46 = 70 ms delay */
> -	mipi_dsi_msleep(&dsi_ctx, 70);
> -
> -	mipi_dsi_dcs_set_display_on_multi(&dsi_ctx);
> +	/* 80 ms delay as per DCS spec / downstream timing */
> +	msleep(80);
> 
>  	/* Send rest of the init cmds */
>  	if (pinfo->desc->send_init_cmds_2)
>  		pinfo->desc->send_init_cmds_2(&dsi_ctx);
> 
> -	mipi_dsi_msleep(&dsi_ctx, 120);
> -
>  	if (dsi_ctx.accum_err < 0)
> -		gpiod_set_value(pinfo->reset_gpio, 0);
> +		gpiod_set_value_cansleep(pinfo->reset_gpio, 0);
> +
> +	return dsi_ctx.accum_err;
> +}
> +
> +static int nt36672a_panel_enable(struct drm_panel *panel)
> +{
> +	struct nt36672a_panel *pinfo = to_nt36672a_panel(panel);
> +	struct mipi_dsi_multi_context dsi_ctx = { .dsi = pinfo->link };
> +
> +	mipi_dsi_dcs_set_display_on_multi(&dsi_ctx);
> +
> +	/* Frame settling delay */
> +	msleep(20);
> +
> +	return dsi_ctx.accum_err;
> +}
> +
> +static int nt36672a_panel_disable(struct drm_panel *panel)
> +{
> +	struct nt36672a_panel *pinfo = to_nt36672a_panel(panel);
> +	struct mipi_dsi_multi_context dsi_ctx = { .dsi = pinfo->link };
> +
> +	mipi_dsi_dcs_set_display_off_multi(&dsi_ctx);
> +
> +	/* 120ms delay as per DCS spec */
> +	msleep(120);
> 
>  	return dsi_ctx.accum_err;
>  }
> @@ -189,6 +204,8 @@ static int nt36672a_panel_get_modes(struct 
> drm_panel *panel,
>  static const struct drm_panel_funcs panel_funcs = {
>  	.unprepare = nt36672a_panel_unprepare,
>  	.prepare = nt36672a_panel_prepare,
> +	.enable = nt36672a_panel_enable,
> +	.disable = nt36672a_panel_disable,
As far as I know adding .enable and .disable callbacks for on/off 
commands is a workaround for -110 time outs
and not a proper fix, as a workaround .disable is enough.
Here is an another attempt with the same workaround and it was declined:
https://lore.kernel.org/all/20240509-jdi-use-disable-v1-1-5c175b2ea1ee@gmail.com/
We have this commit for this issue at downstream 
https://github.com/msm8953-mainline/linux/commit/c1adb576d7b49833d0d48c5ffae18372c9db668e
but in my understanding it also should not considered a proper fix.
>  	.get_modes = nt36672a_panel_get_modes,
>  };
> 
> @@ -404,6 +421,79 @@ static const struct nt36672a_panel_desc 
> tianma_fhd_video_panel_desc = {
>  	.send_deinit_cmds = tianma_fhd_video_send_deinit_cmds,
>  };
> 
> +static void tianma_ginkgo_send_init_cmds(struct mipi_dsi_multi_context 
> *dsi_ctx)
> +{
> +	/* Page 0x25 init */
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xff, 0x25);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xfb, 0x01);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x18, 0x96);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x05, 0x04);
> +
> +	/* Page 0x20 init */
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xff, 0x20);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xfb, 0x01);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x78, 0x01);
> +
> +	/* Page 0x24 init */
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xff, 0x24);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xfb, 0x01);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x82, 0x13);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x84, 0x31);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x88, 0x13);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x8a, 0x31);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x8e, 0xe4);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x8f, 0x01);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x90, 0x80);
> +
> +	/* Page 0x26 init */
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xff, 0x26);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xfb, 0x01);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xa9, 0x12);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xaa, 0x10);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xae, 0x8a);
> +
> +	/* Page 0x10 (User command page) */
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xff, 0x10);
> +}
> +
> +static void tianma_ginkgo_send_post_on_cmds(struct 
> mipi_dsi_multi_context *dsi_ctx)
> +{
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0xb0, 0x01);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x35, 0x00);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x68, 0x04, 0x03);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x51, 0xb8);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x53, 0x2c);
> +	mipi_dsi_dcs_write_seq_multi(dsi_ctx, 0x55, 0x00);
> +}
> +
> +static const struct drm_display_mode tianma_ginkgo_fhd_video_mode = {
> +	.clock		= 183025,
> +
> +	.hdisplay	= 1080,
> +	.hsync_start	= 1080 + 90,
> +	.hsync_end	= 1080 + 90 + 2,
> +	.htotal		= 1080 + 90 + 2 + 120,
> +
> +	.vdisplay	= 2340,
> +	.vsync_start	= 2340 + 10,
> +	.vsync_end	= 2340 + 10 + 3,
> +	.vtotal		= 2340 + 10 + 3 + 8,
> +
> +	.type = DRM_MODE_TYPE_DRIVER | DRM_MODE_TYPE_PREFERRED,
> +};
> +
> +static const struct nt36672a_panel_desc 
> tianma_ginkgo_fhd_video_panel_desc = {
> +	.display_mode = &tianma_ginkgo_fhd_video_mode,
> +	.panel_name = "tianma-ginkgo-fhd-video",
> +	.width_mm = 67,
> +	.height_mm = 145,
> +	.mode_flags = MIPI_DSI_MODE_VIDEO | MIPI_DSI_MODE_LPM,
> +	.format = MIPI_DSI_FMT_RGB888,
> +	.lanes = 4,
> +	.send_init_cmds_1 = tianma_ginkgo_send_init_cmds,
> +	.send_init_cmds_2 = tianma_ginkgo_send_post_on_cmds,
> +};
> +
>  static int nt36672a_panel_add(struct nt36672a_panel *pinfo)
>  {
>  	struct device *dev = &pinfo->link->dev;
> @@ -428,6 +518,8 @@ static int nt36672a_panel_add(struct nt36672a_panel 
> *pinfo)
>  	if (ret)
>  		return dev_err_probe(dev, ret, "Failed to get backlight\n");
> 
> +	pinfo->base.prepare_prev_first = true;
> +
>  	drm_panel_add(&pinfo->base);
> 
>  	return 0;
> @@ -481,6 +573,7 @@ static void nt36672a_panel_remove(struct 
> mipi_dsi_device *dsi)
> 
>  static const struct of_device_id tianma_fhd_video_of_match[] = {
>  	{ .compatible = "tianma,fhd-video", .data = 
> &tianma_fhd_video_panel_desc },
> +	{ .compatible = "tianma,fhd-video-ginkgo", .data = 
> &tianma_ginkgo_fhd_video_panel_desc },
>  	{ },
>  };
>  MODULE_DEVICE_TABLE(of, tianma_fhd_video_of_match);