Unlike the original deleted Matrox mga driver, the new mgag200 driver
has the frame-buffer RGBX swapped on big-endian RISC systems. Fix by
enabling byte swapping "PowerPC" OPMODE for any __BIG_ENDIAN config.

Fixes: 414c45310625 ("mgag200: initial g200se driver (v2)")
Signed-off-by: René Rebe <rene@exactco.de>
---
Tested on IBM 43p Model 150 (7043-150) running T2/Linux.
---
 drivers/gpu/drm/mgag200/mgag200_mode.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index 951d715dea30..9073063f6473 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -655,6 +655,20 @@ void mgag200_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_
 	else
 		mgag200_crtc_fill_gamma(mdev, format);
 
+#ifdef __BIG_ENDIAN
+	/* Big-endian byte-swapping */
+	switch (format->format) {
+	case DRM_FORMAT_RGB565:
+		WREG32(MGAREG_OPMODE, 1 << 16);
+		break;
+	case DRM_FORMAT_XRGB8888:
+		WREG32(MGAREG_OPMODE, 2 << 16);
+		break;
+	default:
+		break;
+	}
+#endif
+
 	mgag200_enable_display(mdev);
 }
 
-- 
2.46.0

-- 
René Rebe, ExactCODE GmbH, Berlin, Germany
https://exactco.de • https://t2linux.com • https://patreon.com/renerebe

Hi,

let's first go through the ast patch. Most of that review also applies 
to this driver.

Best regards
Thomas

Am 02.12.25 um 16:42 schrieb René Rebe:
> Unlike the original deleted Matrox mga driver, the new mgag200 driver
> has the frame-buffer RGBX swapped on big-endian RISC systems. Fix by
> enabling byte swapping "PowerPC" OPMODE for any __BIG_ENDIAN config.
>
> Fixes: 414c45310625 ("mgag200: initial g200se driver (v2)")
> Signed-off-by: René Rebe <rene@exactco.de>
> ---
> Tested on IBM 43p Model 150 (7043-150) running T2/Linux.
> ---
>   drivers/gpu/drm/mgag200/mgag200_mode.c | 14 ++++++++++++++
>   1 file changed, 14 insertions(+)
>
> diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
> index 951d715dea30..9073063f6473 100644
> --- a/drivers/gpu/drm/mgag200/mgag200_mode.c
> +++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
> @@ -655,6 +655,20 @@ void mgag200_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_
>   	else
>   		mgag200_crtc_fill_gamma(mdev, format);
>   
> +#ifdef __BIG_ENDIAN
> +	/* Big-endian byte-swapping */
> +	switch (format->format) {
> +	case DRM_FORMAT_RGB565:
> +		WREG32(MGAREG_OPMODE, 1 << 16);
> +		break;
> +	case DRM_FORMAT_XRGB8888:
> +		WREG32(MGAREG_OPMODE, 2 << 16);
> +		break;
> +	default:
> +		break;
> +	}
> +#endif
> +
>   	mgag200_enable_display(mdev);
>   }
>   

-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstr. 146, 90461 Nürnberg, Germany, www.suse.com
GF: Jochen Jaser, Andrew McDonald, Werner Knoblich, (HRB 36809, AG Nürnberg)