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Lyude Paul 662884a9ad drm/i915: Fix DPCD register order in intel_dp_aux_enable_backlight()
For eDP panels, it appears it's expected that so long as the panel is in
DPCD control mode that the brightness value is never set to 0. Instead,
if the desired effect is to set the panel's backlight to 0 we're
expected to simply turn off the backlight through the
DP_EDP_DISPLAY_CONTROL_REGISTER.

We already do the latter correctly in intel_dp_aux_disable_backlight().
But, we make the mistake of writing the DPCD registers in the wrong
order when enabling the backlight in intel_dp_aux_enable_backlight()
since we currently enable the backlight through
DP_EDP_DISPLAY_CONTROL_REGISTER before writing the brightness level. On
the X1 Extreme 2nd Generation, this appears to have the potential of
confusing the panel in such a way that further attempts to set the
brightness don't actually change the backlight as expected and leave it
off. Presumably, this happens because the incorrect register writing
order briefly leaves the panel with DPCD mode enabled and a 0 brightness
level set.

So, reverse the order we write the DPCD registers when enabling the
panel backlight so that we write the brightness value first, and enable
the backlight second. This fix appears to be the final bit needed to get
the backlight on the ThinkPad X1 Extreme 2nd Generation's AMOLED screen
working.

Tested-by: AceLan Kao <acelan.kao@canonical.com>
Tested-by: Perry Yuan <pyuan@redhat.com>
Signed-off-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200116211623.53799-4-lyude@redhat.com
History 2020-01-17 13:41:06 +02:00
arch Merge drm/drm-next into drm-intel-next-queued 2020-01-09 17:19:12 +02:00
block for-linus-20191212 2019-12-13 14:27:19 -08:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
Documentation dt-bindings: fix warnings in xinpeng,xpp055c272.yaml 2020-01-06 19:43:40 +01:00
drivers drm/i915: Fix DPCD register order in intel_dp_aux_enable_backlight() 2020-01-17 13:41:06 +02:00
fs Merge branch 'remove-ksys-mount-dup' of git://git.kernel.org/pub/scm/linux/kernel/git/brodo/linux 2019-12-15 11:36:12 -08:00
include Merge drm/drm-next into drm-intel-next-queued 2020-01-09 17:19:12 +02:00
init fs: remove ksys_dup() 2019-12-12 19:00:36 +01:00
ipc treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
kernel treewide conversion from FIELD_SIZEOF() to sizeof_field() 2019-12-13 14:02:12 -08:00
lib lib: raid6: fix awk build warnings 2019-12-09 18:55:03 +01:00
LICENSES LICENSES: Rename other to deprecated 2019-05-03 06:34:32 -06:00
mm Merge branch 'akpm' (patches from Andrew) 2019-12-05 09:46:26 -08:00
net io_uring-5.5-20191212 2019-12-13 14:24:54 -08:00
samples drm-misc-next for v5.6: 2019-12-17 13:57:54 +01:00
scripts pr_warning() removal for 5.5 2019-12-09 11:48:21 -08:00
security treewide: Use sizeof_field() macro 2019-12-09 10:36:44 -08:00
sound sound fixes for 5.5-rc2 2019-12-13 14:40:38 -08:00
tools drm-misc-next for v5.6: 2020-01-03 11:43:44 +10:00
usr arch: sembuf.h: make uapi asm/sembuf.h self-contained 2019-12-04 19:44:14 -08:00
virt KVM: Fix jump label out_free_* in kvm_init() 2019-11-23 11:29:17 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap Update mailmap info for Steve Wise 2019-12-09 13:49:25 -05:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS Linux 5.4-rc4 2019-10-29 04:43:29 -06:00
Kbuild kbuild: do not descend to ./Kbuild when cleaning 2019-08-21 21:03:58 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS drm-misc-next for v5.6: 2019-12-17 13:57:54 +01:00
Makefile Linux 5.5-rc2 2019-12-15 15:16:08 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

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.