[Mesa-dev] [PATCH] st/mesa: update the blend before a full color clear

[Gurchetan Singh]

On Thu, Feb 8, 2018 at 5:15 PM, Marek Olšák <maraeo at gmail.com> wrote:
>
> On Fri, Feb 9, 2018 at 2:12 AM, Gurchetan Singh
> <gurchetansingh at chromium.org> wrote:
> > On Thu, Feb 8, 2018 at 4:46 PM, Marek Olšák <maraeo at gmail.com> wrote:
> >>
> >> This is not the correct fix.
> >>
> >> clear_with_quad calls cso_set_blend. pipe->clear ignores (and should
> >> ignore) the blend state. There is no scenario where you would have to
> >> call st_update_blend for pipe->clear. I think this is a virgl bug in
> >> pipe->clear.
> >
> >
> > clear_with_quad is only called if a color mask exists (see is_color_masked).
> > When the state transitions from color-mask exists --> completely unmasked
> > (the clear_buffers case), how is the driver supposed to be notified?
>
> The driver isn't notified. It should ignore the blend state entirely
> and always use the full mask for full clears.

That was my first approach (see crrev.com/c/909961).  However, that
causes an issue where we:

1) Set blendstate B in cso_set_blend, thereby putting it into the cso cache
2) Do a full clear (thereby altering the colormask on the host side,
but not updating the cso blendstate)
3) Try to use blendstate B again.  Since the cso context still thinks
we have blendstate B, it never calls ctx->pipe->bind_blend_state.

Besides updating the cso state, how can I fix this issue?

>
>
> Marek