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The source for the Linux kernel used in Windows Subsystem for Linux 2 (WSL2)
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Tomi Valkeinen 547d528ea3 drm/omap: fix memory barrier bug in DMM driver 
[ Upstream commit 538f66ba20 ]

A DMM timeout "timed out waiting for done" has been observed on DRA7
devices. The timeout happens rarely, and only when the system is under
heavy load.

Debugging showed that the timeout can be made to happen much more
frequently by optimizing the DMM driver, so that there's almost no code
between writing the last DMM descriptors to RAM, and writing to DMM
register which starts the DMM transaction.

The current theory is that a wmb() does not properly ensure that the
data written to RAM is observable by all the components in the system.

This DMM timeout has caused interesting (and rare) bugs as the error
handling was not functioning properly (the error handling has been fixed
in previous commits):

 * If a DMM timeout happened when a GEM buffer was being pinned for
   display on the screen, a timeout error would be shown, but the driver
   would continue programming DSS HW with broken buffer, leading to
   SYNCLOST floods and possible crashes.

 * If a DMM timeout happened when other user (say, video decoder) was
   pinning a GEM buffer, a timeout would be shown but if the user
   handled the error properly, no other issues followed.

 * If a DMM timeout happened when a GEM buffer was being released, the
   driver does not even notice the error, leading to crashes or hang
   later.

This patch adds wmb() and readl() calls after the last bit is written to
RAM, which should ensure that the execution proceeds only after the data
is actually in RAM, and thus observable by DMM.

The read-back should not be needed. Further study is required to understand
if DMM is somehow special case and read-back is ok, or if DRA7's memory
barriers do not work correctly.

Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2018-11-21 09:24:03 +01:00
Documentation media: media colorspaces*.rst: rename AdobeRGB to opRGB 2018-11-13 11:15:12 -08:00
arch powerpc/mm: Don't report hugepage tables as memory leaks when using kmemleak 2018-11-21 09:24:03 +01:00
block block, bfq: correctly charge and reset entity service in all cases 2018-11-13 11:14:55 -08:00
certs Replace magic for trusting the secondary keyring with #define 2018-09-09 19:55:54 +02:00
crypto crypto: tcrypt - fix ghash-generic speed test 2018-11-13 11:15:07 -08:00
drivers drm/omap: fix memory barrier bug in DMM driver 2018-11-21 09:24:03 +01:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs Btrfs: fix fsync after hole punching when using no-holes feature 2018-11-13 11:15:18 -08:00
include TC: Set DMA masks for devices 2018-11-13 11:15:11 -08:00
init init: rename and re-order boot_cpu_state_init() 2018-08-15 18:12:48 +02:00
ipc ipc/sem.c: prevent queue.status tearing in semop 2018-09-05 09:26:30 +02:00
kernel bpf: wait for running BPF programs when updating map-in-map 2018-11-13 11:15:18 -08:00
lib locking/lockdep: Fix debug_locks off performance problem 2018-11-13 11:14:51 -08:00
mm mm/rmap: map_pte() was not handling private ZONE_DEVICE page properly 2018-11-13 11:15:08 -08:00
net net: sched: Remove TCA_OPTIONS from policy 2018-11-13 11:15:18 -08:00
samples samples/bpf: Check the error of write() and read() 2018-08-24 13:09:12 +02:00
scripts kconfig: fix the rule of mainmenu_stmt symbol 2018-11-04 14:52:45 +01:00
security ima: fix showing large 'violations' or 'runtime_measurements_count' 2018-11-13 11:15:08 -08:00
sound ASoC: intel: skylake: Add missing break in skl_tplg_get_token() 2018-11-13 11:15:05 -08:00
tools selftests/powerpc: Fix ptrace tm failure 2018-11-13 11:15:13 -08:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm64: Fix caching of host MDCR_EL2 value 2018-11-13 11:15:08 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
…
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dt-bindings: Document mti,mips-cpc binding 2018-03-15 10:54:35 +01:00
Makefile Linux 4.14.81 2018-11-13 11:15:18 -08:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

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.