[Bug 84108] New: [ILK] [sna gen 5] Delayed drawing of strings and characters.

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=84108

          Priority: medium
            Bug ID: 84108
          Assignee: chris at chris-wilson.co.uk
           Summary: [ILK] [sna gen 5] Delayed drawing of strings and
                    characters.
        QA Contact: intel-gfx-bugs at lists.freedesktop.org
          Severity: normal
    Classification: Unclassified
                OS: Linux (All)
          Reporter: hamer.mk at gmail.com
          Hardware: x86-64 (AMD64)
            Status: NEW
           Version: unspecified
         Component: Driver/intel
           Product: xorg

Created attachment 106568
  --> https://bugs.freedesktop.org/attachment.cgi?id=106568&action=edit
Restoration of one hunk from fb51ec4

I have Lenovo ThinkPad X201 tablet with Intel Core i7 L-620 (Intel HD Graphics
gen 5).

Somewhere around version 2.99.912 of xf86-video-intel I got a strange bug: when
I scroll page in browser the refreshing of screen is delayed or when I type
text the symbols appear not after each one but after every second symbol.

I found that problem starts after commit:
commit fb51ec44f4b6069ab854233d5d0da34eb79f754c
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Mon Jun 23 09:07:13 2014 +0100

    sna: Rename IGNORE_CPU to IGNORE_DAMAGE to better reflect its purpose

    Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

I found that if I restore only one hunk (4th hunk in file
«src/sna/sna_accel.c») from this commit the bug disappears. By this hunk the
one line in «src/sna/sna_accel.c» was changed but not just renamed:
from: (flags & REPLACES || !priv->gpu_damage.....
to: (flags & (REPLACES | IGNORE_DAMAGE) || !priv->gpu_damage.....

But according to bug #79993 this maybe not a root cause. But I don't know why
my patch works...

Please see video here: http://youtu.be/JjAScg4MZNk
On «test 1» and «test 2» I use clean driver from git and symbols printed with
delay.
On «test 3» and «test 4» I use attached patch and symbols printed normally.

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