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Ville Syrjälä a87e55f89f drm/i915: Fix vblank timestamp/frame counter jumps on gen2
Previously I was under the impression that the scanline counter
reads 0 when the pipe is off. Turns out that's not correct, and
instead the scanline counter simply stops when the pipe stops, and
it retains it's last value until the pipe starts up again, at which
point the scanline counter jumps to vblank start.

These jumps can cause the timestamp to jump backwards by one frame.
Since we use the timestamps to guesstimage also the frame counter
value on gen2, that would cause the frame counter to also jump
backwards, which leads to a massice difference from the previous value.
The end result is that flips/vblank events don't appear to complete as
they're stuck waiting for the frame counter to catch up to that massive
difference.

Fix the problem properly by actually making sure the scanline counter
has started to move before we assume that it's safe to enable vblank
processing.

v2: Less pointless duplication in the code (Chris)

Cc: stable@vger.kernel.org
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Fixes: b7792d8b54 ("drm/i915: Wait for pipe to start before sampling vblank timestamps on gen2")
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171129153732.3612-1-ville.syrjala@linux.intel.com
(cherry picked from commit 8fedd64dab)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
2017-12-05 16:56:36 +02:00
arch Merge branch 'fixes' of git://git.armlinux.org.uk/~rmk/linux-arm 2017-12-03 10:51:08 -05:00
block Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2017-11-28 16:22:10 -08:00
Documentation hwmon fixes for v4.15-rc2 2017-12-03 10:46:16 -05:00
drivers drm/i915: Fix vblank timestamp/frame counter jumps on gen2 2017-12-05 16:56:36 +02:00
firmware kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
fs NFS client fixes for Linux 4.15-rc2 2017-12-01 20:04:20 -05:00
include RISC-V Cleanups and ABI Fixes for 4.15-rc2 2017-12-01 19:39:12 -05:00
init EXPERT Kconfig menu: fix broken EXPERT menu 2017-11-17 16:10:05 -08:00
ipc Rename superblock flags (MS_xyz -> SB_xyz) 2017-11-27 13:05:09 -08:00
kernel Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
lib RISC-V Cleanups and ABI Fixes for 4.15-rc2 2017-12-01 19:39:12 -05:00
mm Merge branch 'for-linus' of git://git.kernel.dk/linux-block 2017-12-01 08:05:45 -05:00
net NFS client fixes for Linux 4.15-rc2 2017-12-01 20:04:20 -05:00
samples kbuild: remove all dummy assignments to obj- 2017-11-18 11:46:06 +09:00
scripts Merge branch 'akpm' (patches from Andrew) 2017-11-29 19:12:44 -08:00
security bug fixes: 2017-11-30 18:56:41 -05:00
sound Revert "ALSA: usb-audio: Fix potential zero-division at parsing FU" 2017-11-28 09:34:36 -08:00
tools Power management fixes for v4.15-rc2 2017-11-30 18:45:55 -05:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt * x86 bugfixes: APIC, nested virtualization, IOAPIC 2017-11-30 08:15:19 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore Kbuild misc updates for v4.15 2017-11-17 17:51:33 -08:00
.mailmap Add Jason Gunthorpe as co-maintainer of the RDMA stack 2017-11-17 09:36:18 -08:00
COPYING
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild Kbuild updates for v4.15 2017-11-17 17:45:29 -08:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS hwmon fixes for v4.15-rc2 2017-12-03 10:46:16 -05:00
Makefile Linux 4.15-rc2 2017-12-03 11:01:47 -05:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

Linux kernel
============

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.