Hi,
thanks for the update.
Am 05.12.25 um 18:24 schrieb René Rebe:
Unlike the original, deleted Matrox mga driver, the new mgag200 driver
has the XRGB frame-buffer byte 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 <[email protected]>
Cc: [email protected]
---
V2: move to atomic_update
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..d40434ec68ab 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -496,6 +496,20 @@ void mgag200_primary_plane_helper_atomic_update(struct
drm_plane *plane,
struct drm_atomic_helper_damage_iter iter;
struct drm_rect damage;
+#ifdef __BIG_ENDIAN
+ /* Big-endian byte-swapping */
+ switch (fb->format->format) {
+ case DRM_FORMAT_RGB565:
+ WREG32(MGAREG_OPMODE, 0x10100);
+ break;
+ case DRM_FORMAT_XRGB8888:
+ WREG32(MGAREG_OPMODE, 0x20200);
+ break;
+ default:
+ break;
No need for a default branch IIRC.
+ }
This is the right place to set up the write mode.
But looking at the G200 docs, I found that the reset value for OPMODE
has bit 18 set to 1. These writes clear the value. If that intentional?
For better style and compatibility, I suggest to first read the value
and keep the reserved bit as-is.
u32 opmode
opmode = RREG32(MGAREG_OPMODE)
opmode &= ~GENMASK(17, 16)
opmode &= ~GENMASK(9, 8)
opmode &= ~GENMASK(3, 2)
switch (format) {
opmode |= ...;
}
WREG32(OPMODE, opmode);
You can put that in a helper near set_startadd [1]
void mgag200_set_datasiz(struct mga_device *mdev, u32 format)
{
#if __BIG_ENDIAN
...
#endif
}
Then call that from atomic_update and it should be fine.
[1]
https://elixir.bootlin.com/linux/v6.18/source/drivers/gpu/drm/mgag200/mgag200_mode.c#L117
Best regards
Thomas
+#endif
+
drm_atomic_helper_damage_iter_init(&iter, old_plane_state, plane_state);
drm_atomic_for_each_plane_damage(&iter, &damage) {
mgag200_handle_damage(mdev, shadow_plane_state->data, fb,
&damage);
--
--
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)
