[RFC PATCH xserver] modesetting: re-set the crtc's mode when link-status goes BAD

[Daniel Vetter]

On Mon, Apr 3, 2017 at 8:25 AM, Manasi Navare <manasi.d.navare at intel.com> wrote:
>> So in that case you do need userspace to re-request the same mode at the
>> same bpp?
>
> So yes because when userspace requests the same mode at same bpp,
> kernel will still call intel_dp->mod_valid which validates the mode
> against 18bpp so if the requested mode can be displayed at the lowest of
> 18bpp, then the kernel will try to do the modeset for that mode at lower
> bpp. What I am trying to say is irrespective of what bpp userspace requests,
> kernel will check if it can display that at the lowest of 18bpp.

You're talking about two different bpp here I think. Eric talks about
the pixel format of the framebuffer, Manasi here about the bpp we send
over the wire. The kernel will auto-dither if the wire bpp is lower
than the stuff we scan out. Same with 6bpc panels really.

Right now userspace can't request a specific bpp for the sink/pipe,
that's fully under the kernel's control. It only gets to set the pixel
format of fbs.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch