drm/tiny: panel-mipi-dbi: Use drm_client_setup_with_fourcc()

PATCH Applied Fabio Estevam 3 participants 4 messages Apr 17, 2025 – May 12, 2025

Subsystems (4)

Stable branch DRM drivers DRM misc DRM driver for MIPI dbi compatible panels

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Fabio Estevam

author

2025-04-17 10:35 UTC #0 lore raw

PATCH v2 1/1 drm/tiny: panel-mipi-dbi: Use drm_client_setup_with_fourcc()

From: Fabio Estevam <[email protected]>

Since commit 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default"), RGB565 displays such as the CFAF240320X no longer render correctly: colors are distorted and the content is shown twice horizontally.

This regression is due to the fbdev emulation layer defaulting to 32 bits per pixel, whereas the display expects 16 bpp (RGB565). As a result, the framebuffer data is incorrectly interpreted by the panel.

Fix the issue by calling drm_client_setup_with_fourcc() with a format explicitly selected based on the display's bits-per-pixel value. For 16 bpp, use DRM_FORMAT_RGB565; for other values, fall back to the previous behavior. This ensures that the allocated framebuffer format matches the hardware expectations, avoiding color and layout corruption.

Tested on a CFAF240320X display with an RGB565 configuration, confirming correct colors and layout after applying this patch.

Cc [email protected]

Fixes 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default")

Signed-off-by Fabio Estevam <[email protected]>

Reviewed-by Thomas Zimmermann <[email protected]>

---
Changes since v1:
- Improved the commit log.
- Added Thomas' Reviewed-by tag.
- Added more maintainers on Cc as panel-mipi-dbi.c has been marked as orphan.

 drivers/gpu/drm/tiny/panel-mipi-dbi.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

drivers/gpu/drm/tiny/panel-mipi-dbi.c +4 -1

index 0460ecaef4bd..23914a9f7fd3 100644
@@ -390,7 +390,10 @@ static int panel_mipi_dbi_spi_probe(struct spi_device *spi)
 
 	spi_set_drvdata(spi, drm);
 
-	drm_client_setup(drm, NULL);
+	if (bpp == 16)
+		drm_client_setup_with_fourcc(drm, DRM_FORMAT_RGB565);
+	else
+		drm_client_setup_with_fourcc(drm, DRM_FORMAT_RGB888);
 
 	return 0;
 }

Signature · 1 line

2.34.1

Javier Martinez Canillas

Reviewed-by on v2 1/1

2025-04-22 21:53 UTC #1 lore raw

Fabio Estevam <[email protected]> writes:

Hello Fabio,

Quoted 17 lines

From: Fabio Estevam <[email protected]>
Since commit 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default"), RGB565 displays such as the CFAF240320X no longer render correctly: colors are distorted and the content is shown twice horizontally.
This regression is due to the fbdev emulation layer defaulting to 32 bits per pixel, whereas the display expects 16 bpp (RGB565). As a result, the framebuffer data is incorrectly interpreted by the panel.
Fix the issue by calling drm_client_setup_with_fourcc() with a format explicitly selected based on the display's bits-per-pixel value. For 16 bpp, use DRM_FORMAT_RGB565; for other values, fall back to the previous behavior. This ensures that the allocated framebuffer format matches the hardware expectations, avoiding color and layout corruption.

Quoted 8 lines

Tested on a CFAF240320X display with an RGB565 configuration, confirming correct colors and layout after applying this patch.
Cc [email protected]
Fixes 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default")
Signed-off-by Fabio Estevam <[email protected]>
Reviewed-by Thomas Zimmermann <[email protected]>
---

Reviewed-by Javier Martinez Canillas <[email protected]>

Signature · 5 lines

Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat

Fabio Estevam

author

2025-05-09 11:06 UTC #2 lore raw

Hi Javier and Thomas,

Quoted 25 lines · Javier Martinez Canillas

Fabio Estevam <[email protected]> writes:
Hello Fabio,
Quoted 20 lines
From: Fabio Estevam <[email protected]>
Since commit 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default"), RGB565 displays such as the CFAF240320X no longer render correctly: colors are distorted and the content is shown twice horizontally.
This regression is due to the fbdev emulation layer defaulting to 32 bits per pixel, whereas the display expects 16 bpp (RGB565). As a result, the framebuffer data is incorrectly interpreted by the panel.
Fix the issue by calling drm_client_setup_with_fourcc() with a format explicitly selected based on the display's bits-per-pixel value. For 16 bpp, use DRM_FORMAT_RGB565; for other values, fall back to the previous behavior. This ensures that the allocated framebuffer format matches the hardware expectations, avoiding color and layout corruption.
Tested on a CFAF240320X display with an RGB565 configuration, confirming correct colors and layout after applying this patch.

Quoted 7 lines

Quoted 5 lines
Cc [email protected]
Fixes 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default")
Signed-off-by Fabio Estevam <[email protected]>
Reviewed-by Thomas Zimmermann <[email protected]>
---
Reviewed-by Javier Martinez Canillas <[email protected]>

Could you please help apply this fix?

Thanks

Thomas Zimmermann

maintainer Applied

2025-05-12 06:58 UTC #3 lore raw

Am 09.05.25 um 13:06 schrieb Fabio Estevam:

Quoted 28 lines

Hi Javier and Thomas,
Quoted 24 lines · Javier Martinez Canillas
Fabio Estevam <[email protected]> writes:
Hello Fabio,
Quoted 20 lines
From: Fabio Estevam <[email protected]>
Since commit 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default"), RGB565 displays such as the CFAF240320X no longer render correctly: colors are distorted and the content is shown twice horizontally.
This regression is due to the fbdev emulation layer defaulting to 32 bits per pixel, whereas the display expects 16 bpp (RGB565). As a result, the framebuffer data is incorrectly interpreted by the panel.
Fix the issue by calling drm_client_setup_with_fourcc() with a format explicitly selected based on the display's bits-per-pixel value. For 16 bpp, use DRM_FORMAT_RGB565; for other values, fall back to the previous behavior. This ensures that the allocated framebuffer format matches the hardware expectations, avoiding color and layout corruption.
Tested on a CFAF240320X display with an RGB565 configuration, confirming correct colors and layout after applying this patch.

Quoted 7 lines

Quoted 6 lines
Quoted 5 lines
Cc [email protected]
Fixes 559358282e5b ("drm/fb-helper: Don't use the preferred depth for the BPP default")
Signed-off-by Fabio Estevam <[email protected]>
Reviewed-by Thomas Zimmermann <[email protected]>
---
Reviewed-by Javier Martinez Canillas <[email protected]>
Could you please help apply this fix?

Merged into drm-misc-fixes

Best regards
Thomas

Quoted 2 lines

Thanks

Signature · 7 lines

--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)