drm/fbdev-generic: Fix framebuffer on big endian devices

Starting with kernel 6.7, the framebuffer text console is not working
anymore with the virtio-gpu device on s390x hosts. Such big endian fb
devices are usinga different pixel ordering than little endian devices,
e.g. DRM_FORMAT_BGRX8888 instead of DRM_FORMAT_XRGB8888.

This used to work fine as long as drm_client_buffer_addfb() was still
calling drm_mode_addfb() which called drm_driver_legacy_fb_format()
internally to get the right format. But drm_client_buffer_addfb() has
recently been reworked to call drm_mode_addfb2() instead with the
format value that has been passed to it as a parameter (see commit
6ae2ff23aa43 ("drm/client: Convert drm_client_buffer_addfb() to drm_mode_addfb2()").

That format parameter is determined in drm_fbdev_generic_helper_fb_probe()
via the drm_mode_legacy_fb_format() function - which only generates
formats suitable for little endian devices. So to fix this issue
switch to drm_driver_legacy_fb_format() here instead to take the
device endianness into consideration.

Fixes: 6ae2ff23aa43 ("drm/client: Convert drm_client_buffer_addfb() to drm_mode_addfb2()")
Closes: https://issues.redhat.com/browse/RHEL-45158
Signed-off-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240627173530.460615-1-thuth@redhat.com

diff --git a/drivers/gpu/drm/drm_fbdev_generic.c b/drivers/gpu/drm/drm_fbdev_generic.c
index 97e579c33d84ac475014dce41000a4c725eabd92..1e200d815e1a4e53e4c6da6c5be933ef87d46111 100644 (file)
--- a/drivers/gpu/drm/drm_fbdev_generic.c
+++ b/drivers/gpu/drm/drm_fbdev_generic.c
@@ -84,7 +84,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct drm_fb_helper *fb_helper,
                    sizes->surface_width, sizes->surface_height,
                    sizes->surface_bpp);
 
-       format = drm_mode_legacy_fb_format(sizes->surface_bpp, sizes->surface_depth);
+       format = drm_driver_legacy_fb_format(dev, sizes->surface_bpp,
+                                            sizes->surface_depth);
        buffer = drm_client_framebuffer_create(client, sizes->surface_width,
                                               sizes->surface_height, format);
        if (IS_ERR(buffer))