[Intel-gfx] [PATCH 11/12] drm/i915: Check for invalid cloning earlier during modeset

[Ville Syrjälä]

On Wed, Jun 08, 2016 at 02:15:25PM +0100, Chris Wilson wrote:
> On Wed, Jun 08, 2016 at 01:41:46PM +0300, ville.syrjala at linux.intel.com wrote:
> > From: Ville Syrjälä <ville.syrjala at linux.intel.com>
> > 
> > Move the encoder cloning check to happen earlier in the modeset. The
> > main benefit will be that the debug output from a failed modeset will
> > be less confusing as output_types can not indicate an invalid
> > configuration during the later computation stages.
> > 
> > For instance, what happened to me was kms_setmode was attempting one
> > of its invalid cloning checks during which it asked for DP+VGA cloning
> > on HSW. In this case the DP .compute_config() was executed after
> > the FDI .compute_config() leaving the DP link clock (1.62 in this case)
> > in port_clock, and then later the FDI BW computation tried to use that
> > as the FDI link clock (which should always be 2.7). 1.62 x 2 wasn't
> > enough for the mode it was trying to use, and so it ended up rejecting
> > the modeset, not because of an invalid cloning configuration, but
> > because of supposedly running out of FDI bandwidth. Took me a while
> > to figure out what had actually happened.
> 
> Did it reject the 1.62 link clock when you simply removed the
> check_encoder_cloning()? Just checking... :)

Nope. The rejection only happened due to exceeding the max fdi lane
count. I think I had a warn in there somewhere when I originally
submitted the fdi==port_clock patch, but that apparently didn't
survive into the version that eventually got merged.

-- 
Ville Syrjälä
Intel OTC