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Douglas Anderson 52824ca450 drm/panel-edp: Better describe eDP panel delays 
Now that the eDP panel driver only handles eDP panels we can make
better sense of the delays here. Let's describe them in terms of the
standard eDP timing diagram from the eDP spec.

As part of this, it becomes pretty clear that some eDP panels have too
long of a "hpd_reliable_delay". This used to be the "prepare"
delay. It's the fixed delay that we do in the panel driver after
powering on our panel before we look at the HPD signal. To understand
this better, first realize that there could be 3 paths we follow
depending on how HPD is hooked up. Let's walk through them:
1. HPD is handled by the eDP controller driver. Until "recently"
   (commit 48834e6084 ("drm/panel-simple: Support hpd-gpios for
   delaying prepare()") in May 2020) this was the only supported
   way. This is supposed to be when the controller driver gets HPD
   straight to a dedicated pin. In this case the controller driver
   should be waiting for HPD in its pre_enable() routine which should
   be called right after the panel's prepare() function is
   called. That means that the old "prepare" delay was only needed as
   a delay after powering the panel but before looking at HPD.
2. HPD is handled via hpd-gpios in the panel. This is much like #1 but
   much easier to follow since all the handling is in the panel
   driver.
3. The no-hpd case. This is also easy to follow.

In any case, even though it seems like some old panel data was using
this incorrectly, let's not touch the old data structures but we'll
add a note indicating that something seems off.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20210914132020.v5.11.I2d798dd015332661c5895ef744bc8ec5cd2e06ca@changeid
2021-09-20 09:23:39 -07:00
arch arm64: defconfig: Everyone who had PANEL_SIMPLE now gets PANEL_EDP 2021-09-20 09:19:05 -07:00
block block-5.15-2021-09-11 2021-09-11 10:19:51 -07:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2021-08-30 12:57:10 -07:00
Documentation dt-bindings: drm/panel-simple-edp: Introduce generic eDP panels 2021-09-20 09:13:35 -07:00
drivers drm/panel-edp: Better describe eDP panel delays 2021-09-20 09:23:39 -07:00
fs Merge branch 'misc.namei' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2021-09-12 10:43:51 -07:00
include drm/edid: Allow querying/working with the panel ID from the EDID 2021-09-20 09:17:25 -07:00
init More tracing updates for 5.15: 2021-09-09 13:11:15 -07:00
ipc ARM development updates for 5.15: 2021-09-09 13:25:49 -07:00
kernel - Make sure the idle timer expires in hardirq context, on PREEMPT_RT 2021-09-12 11:37:41 -07:00
lib Minor fixes to the processing of the bootconfig tree. 2021-09-11 10:16:30 -07:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm Merge drm/drm-next into drm-misc-next 2021-09-14 09:25:30 +02:00
net virtio,vdpa,vhost: features, fixes 2021-09-11 14:48:42 -07:00
samples kgdb patches for 5.15 2021-09-07 12:08:04 -07:00
scripts RISC-V Patches for the 5.15 Merge Window, Part 2 2021-09-11 14:29:42 -07:00
security Kbuild updates for v5.15 2021-09-03 15:33:47 -07:00
sound sound fixes for 5.15-rc1 2021-09-09 16:05:10 -07:00
tools perf tools changes for v5.15: 2nd batch 2021-09-12 16:18:15 -07:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Drop unused kvm_dirty_gfn_invalid() 2021-09-06 08:23:46 -04:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: update email address of Matthias Fuchs and Thomas Körper 2021-08-19 09:39:44 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: move Murali Karicheri to credits 2021-04-29 15:47:30 -07:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS Merge drm/drm-next into drm-misc-next 2021-09-14 09:25:30 +02:00
Makefile Linux 5.15-rc1 2021-09-12 16:28:37 -07:00
README

README 

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.