On Thu, 01 Oct 2015, Matt Roper <matthew.d.roper@intel.com> wrote:
> When watermark calculation was moved up to the atomic check phase, the
> code was updated to calculate based on in-flight atomic state rather
> than already-committed state.  However the hsw_compute_linetime_wm()
> didn't get updated and continued to pull values out of the
> currently-committed CRTC state.  On platforms that call this function
> (HSW/BDW only), this will cause problems when we go to enable the CRTC
> since we'll pull the current mode (off) rather than the mode we're
> calculating for and wind up with a divide by zero error.
>
> This was an oversight in commit:
>
>         commit a28170f3389f4e42db95e595b0d86384a79de696
>         Author: Matt Roper <matthew.d.roper@intel.com>
>         Date:   Thu Sep 24 15:53:16 2015 -0700
>
>             drm/i915: Calculate ILK-style watermarks during atomic check (v3)
>
> Cc: Jani Nikula <jani.nikula@linux.intel.com>
> Signed-off-by: Matt Roper <matthew.d.roper@intel.com>

Matt, current nightly + "drm/i915: Sanitize watermarks after hardware
state readout" + this still oopses my BDW at boot. dmesg attached.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Technology Center