[Intel-gfx] [RFC xf86-video-intel] sna: Call dirtyfb for all non-tear-free cases

Chris Wilson chris at chris-wilson.co.uk
Tue Mar 22 11:36:20 UTC 2016

On Tue, Mar 22, 2016 at 12:31:09PM +0100, Daniel Vetter wrote:
> On Mon, Mar 21, 2016 at 04:26:55PM -0300, Paulo Zanoni wrote:
> > The sna_mode_wants_tear_free() function tries to detect FBC and PSR
> > based on Kernel module parameters. Currently it fails to detect FBC
> > due to the default enable_fbc value being -1. While this can easily be
> > fixed in the Kernel, I had a conversation with Daniel and he expressed
> > unhappiness with that solution, claiming that yet another different
> > code path just for a feature that should be transparent is not a good
> > way to go, and that we should do proper frontbuffer rendering.
> > 
> > So with this patch, we'll have the DDX issuing dirtyfb calls even if
> > TearFree is not enabled, fixing FBC when i915.enable_fbc=-1.
> > 
> > This fixes a bug that happens on SKL with FBC enabled: if you run
> > lightdm, your login/password won't appear as you type on your
> > keyboard. You have to move the mouse over the input box for them to be
> > displayed.
> > 
> > Cc: Chris Wilson <chris at chris-wilson.co.uk>
> > Signed-off-by: Paulo Zanoni <paulo.r.zanoni at intel.com>
> I thought we need this anyway to get the kernel to allow fbc, since SNA
> ends up mmap some of the drm_framebuffer. Even when they're not
> frontbuffers.

Nope. FBC => sna_mode_wants_tear_free() is true.

Chris Wilson, Intel Open Source Technology Centre

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