Re: [Bug #14380] Video tearing/glitching with T400 laptops

Rafael J. Wysocki
2009-11-17T22:30:42Z

On Tuesday 17 November 2009, Arkadiusz Miskiewicz wrote:
> On Monday 16 of November 2009, Rafael J. Wysocki wrote:
> > This message has been generated automatically as a part of a report
> > of recent regressions.
> >
> > The following bug entry is on the current list of known regressions
> > from 2.6.31. Please verify if it still should be listed and let me know
> > (either way).
>
> It's mostly gone. It still happens for like 1/4s once per 6hours but jbarnes
> asked me to fill separate bug for that and gave such patch for testing (see below).
>
> So far haven't seen 1/4s problem with this patch applied.

Great.

> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index 3ba6546..b2cbf7f 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -2491,6 +2491,8 @@ static void g4x_update_wm(struct drm_device *dev, int planea_clock,
> /* Use ns/us then divide to preserve precision */
> sr_entries = (((sr_latency_ns / line_time_us) + 1) *
> pixel_size * sr_hdisplay) / 1000;
> + if (sr_entries > G4X_FIFO_SIZE)
> + sr_entries = G4X_FIFO_SIZE;
> sr_entries = roundup(sr_entries / cacheline_size, 1);
> DRM_DEBUG("self-refresh entries: %d\n", sr_entries);
> I915_WRITE(FW_BLC_SELF, FW_BLC_SELF_EN);
>
> >
> >
> > Bug-Entry : http://bugzilla.kernel.org/show_bug.cgi?id=14380
> > Subject : Video tearing/glitching with T400 laptops
> > Submitter : Theodore Ts'o <tytso-3s7WtUTddSA@public.gmane.org>
> > Date : 2009-10-02 22:40 (46 days old)
> > References : http://marc.info/?l=linux-kernel&m=125452324520623&w=4
> > Handled-By : Jesse Barnes <jbarnes-Y1mF5jBUw70BENJcbMCuUQ@public.gmane.org>
> > Patch : http://marc.info/?l=linux-kernel&m=125591495325000&w=4

Thanks for the update.

Rafael