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AngeloGioacchino Del Regno b16c310115 pwm: mtk-disp: Configure double buffering before reading in .get_state()
The DISP_PWM controller's default behavior is to always use register
double buffering: all reads/writes are then performed on shadow
registers instead of working registers and this becomes an issue
in case our chosen configuration in Linux is different from the
default (or from the one that was pre-applied by the bootloader).

An example of broken behavior is when the controller is configured
to use shadow registers, but this driver wants to configure it
otherwise: what happens is that the .get_state() callback is called
right after registering the pwmchip and checks whether the PWM is
enabled by reading the DISP_PWM_EN register;
At this point, if shadow registers are enabled but their content
was not committed before booting Linux, we are *not* reading the
current PWM enablement status, leading to the kernel knowing that
the hardware is actually enabled when, in reality, it's not.

The aforementioned issue emerged since this driver was fixed with
commit 0b5ef3429d ("pwm: mtk-disp: Fix the parameters calculated
by the enabled flag of disp_pwm") making it to read the enablement
status from the right register.

Configure the controller in the .get_state() callback to avoid
this desync issue and get the backlight properly working again.

Fixes: 3f2b167349 ("pwm: mtk-disp: Implement atomic API .get_state()")
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Tested-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Reviewed-by: Alexandre Mergnat <amergnat@baylibre.com>
Tested-by: Alexandre Mergnat <amergnat@baylibre.com>
Signed-off-by: Thierry Reding <thierry.reding@gmail.com>
History 2023-04-06 16:23:23 +02:00
arch cpumask: re-introduce constant-sized cpumask optimizations 2023-03-05 14:30:34 -08:00
block block-6.3-2023-03-03 2023-03-03 10:21:39 -08:00
certs Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
crypto Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
Documentation dt-bindings: pwm: Convert Amlogic Meson PWM binding 2023-04-06 15:27:39 +02:00
drivers pwm: mtk-disp: Configure double buffering before reading in .get_state() 2023-04-06 16:23:23 +02:00
fs 17 hotfixes. Eight are for MM and seven are for other parts of the 2023-03-04 13:32:50 -08:00
include cpumask: re-introduce constant-sized cpumask optimizations 2023-03-05 14:30:34 -08:00
init Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
io_uring io_uring-6.3-2023-03-03 2023-03-03 10:25:29 -08:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel A set of updates for the interrupt susbsystem: 2023-03-05 11:19:16 -08:00
lib cpumask: re-introduce constant-sized cpumask optimizations 2023-03-05 14:30:34 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm mm: avoid gcc complaint about pointer casting 2023-03-04 14:03:27 -08:00
net nfsd-6.3 fixes: 2023-03-01 11:03:44 -08:00
rust Rust fixes for 6.3-rc1 2023-03-03 14:51:15 -08:00
samples LoongArch changes for v6.3 2023-03-01 09:27:00 -08:00
scripts Remove Intel compiler support 2023-03-05 10:49:37 -08:00
security capability: just use a 'u64' instead of a 'u32[2]' array 2023-03-01 10:01:22 -08:00
sound sound fixes for 6.3-rc1 2023-03-04 10:53:59 -08:00
tools Changes in this cycle were: 2023-03-02 09:45:34 -08:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM/riscv changes for 6.3 2023-02-15 12:33:28 -05:00
.clang-format cpumask: re-introduce constant-sized cpumask optimizations 2023-03-05 14:30:34 -08:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore .gitignore: ignore *.cover and *.mbx 2023-02-05 18:51:22 +09:00
.mailmap mailmap: map Dikshita Agarwal's old address to his current one 2023-03-02 21:54:24 -08:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS There is no particular theme here - mainly quick hits all over the tree. 2023-02-23 17:55:40 -08:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Adding Christian Brauner as VFS co-maintainer. 2023-03-05 11:11:52 -08:00
Makefile Linux 6.3-rc1 2023-03-05 14:52:03 -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.