[Intel-gfx] [PATCH 1/2] drm/i915: Fix scaler init during CRTC HW state readout

[Greg Kroah-Hartman]

On Thu, Jul 20, 2017 at 12:25:30PM +0300, Imre Deak wrote:
> On Thu, Jul 20, 2017 at 11:58:35AM +0300, Jani Nikula wrote:
> > On Thu, 20 Jul 2017, Imre Deak <imre.deak at intel.com> wrote:
> > > The scaler allocation code depends on a non-zero default value for the
> > > crtc scaler_id, so make sure we initialize the scaler state accordingly
> > > even if the crtc is off. This fixes at least an initial YUV420 modeset
> > > (added in a follow-up patchset by Shashank) when booting with the screen
> > > off: after the initial HW readout and modeset which enables the scaler a
> > > subsequent modeset will disable the scaler which isn't properly
> > > allocated. This results in a funky HW state where the pipe scaler HW
> > > registers can't be modified and the normally black screen is grey and
> > > shifted to the right or jitters.
> > >
> > > The problem was revealed by Shashank's YUV420 patchset and first
> > > reported by Ville.
> > >
> > > Cc: Shashank Sharma <shashank.sharma at intel.com>
> > > Cc: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > Cc: Chandra Konduru <chandra.konduru at intel.com>
> > > Cc: Matt Roper <matthew.d.roper at intel.com>
> > > Cc: <stable at vger.kernel.org> # 4.11.x
> > > Reported-by: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > > Fixes: a1b2278e4dfc ("drm/i915: skylake panel fitting using shared scalers")
> > > Signed-off-by: Imre Deak <imre.deak at intel.com>
> > >
> > > ---
> > >
> > > [ Older stable versions need backporting, so that's for a follow-up ]
> > 
> > I thought we'd annotate cc: stable with all the kernels that need the
> > fix, not according to where the fix applies as-is. In this case, it
> > would be v4.2+, right?
> 
> Hm, not sure. I know that this won't apply before 4.11 and I will have
> to send a backported version anyway. So wanted to save a redundant turn
> around after the automatic cherry picking to those stable versions
> fail.
> 
> Greg, what's the proper tag in this case?

4.2+ and then when you get the "this didn't apply" email, send the
backported patches.  That way the stable maintainers know it "should" be
applied there, but it just doesn't seem to work with the existing patch.

thanks,

greg k-h