Hi Mark.
On Sat, Jul 04, 2020 at 03:16:47PM +0100, Mark Cave-Ayland wrote:
> On 04/07/2020 14:41, Sam Ravnborg wrote:
>
> > I think what is happening is that the bochs driver request a shadow copy
> > for the frambuffer. And with the change to fbops we now use the cfb_
> > functions to write to the shadow framebuffer - which is not in any IO
> > space. So this does not work.
> >
> > So maybe all we need is the fix in drm_fb_helper_dirty_blit_real().
> > If you try to undo the change so fbops is set to &drm_fbdev_fb_ops,
> > but keep the fix in drm_fb_helper_dirty_blit_real() how does it then
> > behave?
>
> Bingo! I just tried that and the framebuffer is now working under qemu-system-sparc64
> again - thank you so much for the help! From what you said I guess
> drm_fb_helper_dirty_blit_real() is responsible syncing the shadow copy?
>
> Below is the current working diff based upon your previous one: it certainly feels
> like the difference in memcpy() behaviour should be hidden away in fb_memcpy_tofb()
> or similar.
>From your feedback so far I thnk the minimal fix would be like this:
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> .. static void drm_fb_helper_dirty_blit_real(struct drm_fb_helper *fb_helper,
> size_t len = (clip->x2 - clip->x1) * cpp;
> unsigned int y;
>
> for (y = clip->y1; y < clip->y2; y++) {
> - memcpy(dst, src, len);
> + fb_memcpy_tofb(dst, src, len);
> src += fb->pitches[0];
> dst += fb->pitches[0];
> }
(Hand edited, patch s not a valid syntax)
But I need feedback from someone that know all this a bit better
to judge if this is an OK change.
For once - this will only work with shadow buffers.
Sam
> diff --git a/include/drm/drm_mode_config.h b/include/drm/drm_mode_config.h
> index 6c3ef49b46b3..dce9adf7d189 100644
> --- a/include/drm/drm_mode_config.h
> +++ b/include/drm/drm_mode_config.h
> @@ -865,6 +865,15 @@ struct drm_mode_config {
> */
> bool prefer_shadow_fbdev;
>
> + /**
> + * @use_cfb_for_fbdev:
> + *
> + * Use cfb variants of drm_fb_helper_cfb_{fillrect,copyarea,imageblit}
> + * The cfb variants are required when the CPU do not allow direct
> + * access to the framebuffer (for example sparc64)
> + */
> + bool use_cfb_for_fbdev;
> +
> /**
> * @quirk_addfb_prefer_xbgr_30bpp:
> *
>
> > I did not find time to follow your instructions to test this myself with
> > qemu - sorry.
>
> No worries, I do appreciate that as a maintainer it can be hard to fit these things
> around life, family, job etc.
>
>
> ATB,
>
> Mark.
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