Panic booting qemu-system-sparc64 with bochs_drm

[Gerd Hoffmann]

> Yes, that's correct - I can confirm that the simplified diff below works:
> 
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 5609e164805f..83af05fac604 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -399,7 +399,7 @@ static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper
> *fb_helper,
>         unsigned int y;
> 
>         for (y = clip->y1; y < clip->y2; y++) {
> -               memcpy(dst, src, len);
> +               fb_memcpy_tofb(dst, src, len);

fb_memcpy_tofb is #defined to sbus_memcpy_toio @ sparc which looks
wrong to me given that this is a pci not a sbus device.  sparc also has
memcpy_toio which looks better to me.

There are blit helpers in drm_format_helper.c which already use
memcpy_toio(), I guess we should do the same here.  Not fully sure we
can use memcpy_toio() unconditionally here.  Given that a shadow
framebuffer makes sense only in case the real framebuffer is not in
normal ram we probably can.

take care,
  Gerd