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

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Date:	Tue, 17 Nov 2009 13:52:18 +0100
From:	Arkadiusz Miskiewicz <a.miskiewicz@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Kernel Testers List <kernel-testers@...r.kernel.org>,
	"Jesse Barnes" <jbarnes@...tuousgeek.org>,
	"Theodore Ts'o" <tytso@....edu>
Subject: Re: [Bug #14380] Video tearing/glitching with T400 laptops

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.

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@....edu>
> 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@...tuousgeek.org>
> Patch		: http://marc.info/?l=linux-kernel&m=125591495325000&w=4
> 


-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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