The way of implementing a flip option follows the existing
panel-samsung-s6e8aa0.c [1][2][3].

The value to flip the screen is taken from a downstream kernel file of
a similar but older panel [4]. The mipi clock [5] for the new panel
samsung-s6e88a0-ams427ap24 matches 461 MHz and a hardware read-out of the
0xcb values corresponds to revision R01 of that older panel [6]. Although
for samsung-s6e88a0-ams427ap24 that's in non-flipped state while in this
older driver it seems to be the other way around. Further up there is a
hint [7] basically saying for revision R01 to change the first word of the
0xcb command from 0x06 to 0x0e, which is actually setting BIT(3) of that
word. This causes a horizontal flip.

[1] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L103
[2] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L207-L211
[3] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L954-L974
[4] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c
[5] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L2027-L2028
[6] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L137-L151
[7] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L66-L74

Signed-off-by: Jakob Hauser <jahau@rocketmail.com>
---
 .../drm/panel/panel-samsung-s6e88a0-ams427ap24.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c b/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
index 6e02b881434d..8372d0d307c8 100644
--- a/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
+++ b/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
@@ -32,6 +32,7 @@ struct s6e88a0_ams427ap24 {
 	struct mipi_dsi_device *dsi;
 	struct regulator_bulk_data *supplies;
 	struct gpio_desc *reset_gpio;
+	bool flip_horizontal;
 };
 
 const struct regulator_bulk_data s6e88a0_ams427ap24_supplies[] = {
@@ -538,6 +539,10 @@ static int s6e88a0_ams427ap24_on(struct s6e88a0_ams427ap24 *ctx)
 	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcc, 0x4c);
 	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf2, 0x03, 0x0d);
 	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf1, 0xa5, 0xa5);
+
+	if (ctx->flip_horizontal)
+		mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcb, 0x0e);
+
 	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0, 0xa5, 0xa5);
 	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfc, 0xa5, 0xa5);
 
@@ -672,6 +677,15 @@ static int s6e88a0_ams427ap24_register_backlight(struct s6e88a0_ams427ap24 *ctx)
 	return ret;
 }
 
+static void s6e88a0_ams427ap24_parse_dt(struct s6e88a0_ams427ap24 *ctx)
+{
+	struct mipi_dsi_device *dsi = ctx->dsi;
+	struct device *dev = &dsi->dev;
+	struct device_node *np = dev->of_node;
+
+	ctx->flip_horizontal = of_property_read_bool(np, "flip-horizontal");
+}
+
 static int s6e88a0_ams427ap24_probe(struct mipi_dsi_device *dsi)
 {
 	struct device *dev = &dsi->dev;
@@ -706,6 +720,8 @@ static int s6e88a0_ams427ap24_probe(struct mipi_dsi_device *dsi)
 		       DRM_MODE_CONNECTOR_DSI);
 	ctx->panel.prepare_prev_first = true;
 
+	s6e88a0_ams427ap24_parse_dt(ctx);
+
 	ret = s6e88a0_ams427ap24_register_backlight(ctx);
 	if (ret < 0)
 		return ret;
-- 
2.39.5

On 22/10/2024 23:33, Jakob Hauser wrote:
> The way of implementing a flip option follows the existing
> panel-samsung-s6e8aa0.c [1][2][3].
> 
> The value to flip the screen is taken from a downstream kernel file of
> a similar but older panel [4]. The mipi clock [5] for the new panel
> samsung-s6e88a0-ams427ap24 matches 461 MHz and a hardware read-out of the
> 0xcb values corresponds to revision R01 of that older panel [6]. Although
> for samsung-s6e88a0-ams427ap24 that's in non-flipped state while in this
> older driver it seems to be the other way around. Further up there is a
> hint [7] basically saying for revision R01 to change the first word of the
> 0xcb command from 0x06 to 0x0e, which is actually setting BIT(3) of that
> word. This causes a horizontal flip.
> 
> [1] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L103
> [2] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L207-L211
> [3] https://github.com/torvalds/linux/blob/v6.11/drivers/gpu/drm/panel/panel-samsung-s6e8aa0.c#L954-L974
> [4] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c
> [5] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L2027-L2028
> [6] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L137-L151
> [7] https://github.com/LineageOS/android_kernel_samsung_msm8930-common/blob/lineage-15.1/drivers/video/msm/mipi_samsung_oled_video_qhd_pt-8930.c#L66-L74
> 
> Signed-off-by: Jakob Hauser <jahau@rocketmail.com>
> ---
>   .../drm/panel/panel-samsung-s6e88a0-ams427ap24.c | 16 ++++++++++++++++
>   1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c b/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
> index 6e02b881434d..8372d0d307c8 100644
> --- a/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
> +++ b/drivers/gpu/drm/panel/panel-samsung-s6e88a0-ams427ap24.c
> @@ -32,6 +32,7 @@ struct s6e88a0_ams427ap24 {
>   	struct mipi_dsi_device *dsi;
>   	struct regulator_bulk_data *supplies;
>   	struct gpio_desc *reset_gpio;
> +	bool flip_horizontal;
>   };
>   
>   const struct regulator_bulk_data s6e88a0_ams427ap24_supplies[] = {
> @@ -538,6 +539,10 @@ static int s6e88a0_ams427ap24_on(struct s6e88a0_ams427ap24 *ctx)
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcc, 0x4c);
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf2, 0x03, 0x0d);
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf1, 0xa5, 0xa5);
> +
> +	if (ctx->flip_horizontal)
> +		mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xcb, 0x0e);
> +
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xf0, 0xa5, 0xa5);
>   	mipi_dsi_dcs_write_seq_multi(&dsi_ctx, 0xfc, 0xa5, 0xa5);
>   
> @@ -672,6 +677,15 @@ static int s6e88a0_ams427ap24_register_backlight(struct s6e88a0_ams427ap24 *ctx)
>   	return ret;
>   }
>   
> +static void s6e88a0_ams427ap24_parse_dt(struct s6e88a0_ams427ap24 *ctx)
> +{
> +	struct mipi_dsi_device *dsi = ctx->dsi;
> +	struct device *dev = &dsi->dev;
> +	struct device_node *np = dev->of_node;
> +
> +	ctx->flip_horizontal = of_property_read_bool(np, "flip-horizontal");


Please use device_property_read_bool() instead

> +}
> +
>   static int s6e88a0_ams427ap24_probe(struct mipi_dsi_device *dsi)
>   {
>   	struct device *dev = &dsi->dev;
> @@ -706,6 +720,8 @@ static int s6e88a0_ams427ap24_probe(struct mipi_dsi_device *dsi)
>   		       DRM_MODE_CONNECTOR_DSI);
>   	ctx->panel.prepare_prev_first = true;
>   
> +	s6e88a0_ams427ap24_parse_dt(ctx);

I don't think this deserves a separate function, just move it probe.

> +
>   	ret = s6e88a0_ams427ap24_register_backlight(ctx);
>   	if (ret < 0)
>   		return ret;

With that changed:

Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org>