Re: [PATCH RFC] drm/i915: reduce cursor size for GEN5 hardware

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Wed, Feb 01, 2017 at 01:41:08PM +0100, Maarten Lankhorst wrote:
> Op 31-01-17 om 20:13 schreef Uwe Kleine-König:
> > Hello,
> >
> > On Tue, Jan 31, 2017 at 10:03:26AM +0100, Maarten Lankhorst wrote:
> >> Op 31-01-17 om 09:09 schreef Uwe Kleine-König:
> >>> From: Chris Wilson <chris@chris-wilson.co.uk>
> >>>
> >>> As the introduced comment admits this is clearly a workaround, but for
> >>> me this is the only known way to make my Lenovo X201 work without
> >>> flickering and crashing.
> >>>
> >>> Signed-off-by: Uwe Kleine-König <uwe@kleine-koenig.org>
> >>> [uwe: added changelog, comment and restrict to GEN5]
> >>> ---
> >>> Hello,
> >>>
> >>> as I don't like having to compile my own kernel (which has this workaround) I
> >>> suggest to apply this patch until someone with more knowledge than me about
> >>> i915 finds the muse and time to work on this.
> >> Just curious, does this help?
> >>
> >> diff --git a/drivers/gpu/drm/i915/intel_pm.c b/drivers/gpu/drm/i915/intel_pm.c
> >> index ae2c0bb4b2e8..13de4c526ca6 100644
> >> --- a/drivers/gpu/drm/i915/intel_pm.c
> >> +++ b/drivers/gpu/drm/i915/intel_pm.c
> >> @@ -1838,7 +1838,7 @@ static uint32_t ilk_compute_cur_wm(const struct intel_crtc_state *cstate,
> >>  	 * this is necessary to avoid flickering.
> >>  	 */
> >>  	int cpp = 4;
> >> -	int width = pstate->base.visible ? pstate->base.crtc_w : 64;
> >> +	int width = 256;
> >>  
> >>  	if (!cstate->base.active)
> >>  		return 0;
> >>
> > On a kernel with this patch applied I cannot reproduce the flickering. I
> > keep that kernel running but expect that it also fixes the crash.
> >
> > Best regards
> > Uwe
> 
> Ok that's good news.
> 
> Maybe ville or matt can comment whether this patch is the right fix?

Well, it's just extending the hack even further. The right fix would be
to fix the wm programming sequence to respect the frame boundaries
correctly (ie. my old vblank based wm stuff).

-- 
Ville Syrjälä
Intel OTC
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