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Maxime Ripard e2771deb5d
drm/sun4i: rgb: Change the pixel clock validation check
The current code, since commit bb43d40d7c ("drm/sun4i: rgb: Validate the
clock rate"), perform some validation on the pixel clock to filter out the
EDID modes provided by monitors (through bridges) that we wouldn't be able
to reach. For the usual modes, we're able to generate a perfect clock rate,
so a strict check was enough.

However, this had the side effect of preventing displays that would work
otherwise to operate properly, since we would pretty much never be able to
generate an exact rate for those displays, even though we would fall within
that panel tolerance.

This was also shown to happen for unusual modes exposed through EDIDs, for
example on eDP panels.

We can work around this by simplifying a bit the problem: no panels we've
encountered so far actually needed that check. All of them are tied to a
particular board when it is produced, and made to work with the Allwinner
BSP. That pretty much guarantees that we never have a pixel clock out of
reach.

On the other hand, the EDIDs modes that needed to be validated have always
been exposed through bridges.

Let's just use that metric to instead of validating all modes, only
validate modes when we have a bridge attached. It should be good enough for
now, while we still have room for improvements or refinements using the
display_timings structure for example for panels.

We also add a tolerance for EDID-based modes instead of doing a strict
check. This tolerance is of 0.5% which is the one advertised in the VESA
DVT and CVT specs. If that needed to be extended in the future, we can add
a custom module parameter to relax it a bit.

Fixes: bb43d40d7c ("drm/sun4i: rgb: Validate the clock rate")
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Tested-by: Vasily Khoruzhick <anarsoul@gmail.com> # tested on pinebook
Reviewed-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ec2dc2a7b3d4bd44f7a2a6e1c1813f92449a7310.1551191081.git-series.maxime.ripard@bootlin.com
2019-03-07 14:46:46 +01:00
Documentation Merge drm/drm-next into drm-misc-next 2019-03-06 09:22:18 -05:00
LICENSES This is a fairly typical cycle for documentation. There's some welcome 2018-10-24 18:01:11 +01:00
arch ARM: SoC fixes for v5.0 2019-03-02 16:43:15 -08:00
block for-linus-20190215 2019-02-15 09:12:28 -08:00
certs kbuild: remove redundant target cleaning on failure 2019-01-06 09:46:51 +09:00
crypto net: crypto set sk to NULL when af_alg_release. 2019-02-18 12:01:24 -08:00
drivers drm/sun4i: rgb: Change the pixel clock validation check 2019-03-07 14:46:46 +01:00
firmware kbuild: change filechk to surround the given command with { } 2019-01-06 09:46:51 +09:00
fs Merge branch 'akpm' (patches from Andrew) 2019-03-01 09:04:59 -08:00
include Merge drm/drm-next into drm-misc-next 2019-03-06 09:22:18 -05:00
init revert "initramfs: cleanup incomplete rootfs" 2019-02-21 09:00:59 -08:00
ipc ipc: IPCMNI limit check for semmni 2018-10-31 08:54:14 -07:00
kernel bpf: fix sanitation rewrite in case of non-pointers 2019-03-01 21:24:08 -08:00
lib kasan: turn off asan-stack for clang-8 and earlier 2019-03-01 09:02:33 -08:00
mm Merge branch 'akpm' (patches from Andrew) 2019-03-01 09:04:59 -08:00
net net: sit: fix memory leak in sit_init_net() 2019-03-02 00:53:23 -08:00
samples samples: mei: use /dev/mei0 instead of /dev/mei 2019-01-30 15:24:45 +01:00
scripts kasan: turn off asan-stack for clang-8 and earlier 2019-03-01 09:02:33 -08:00
security Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2019-02-24 09:28:26 -08:00
sound Merge drm/drm-next into drm-misc-next 2019-03-06 09:22:18 -05:00
tools selftests: fixes for UDP GRO 2019-03-01 11:24:00 -08:00
usr user/Makefile: Fix typo and capitalization in comment section 2018-12-11 00:18:03 +09:00
virt kvm: properly check debugfs dentry before using it 2019-02-28 08:57:32 -08:00
.clang-format clang-format: Update .clang-format with the latest for_each macro list 2019-01-19 19:26:06 +01:00
.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: Add support for DT binding schema checks 2018-12-13 09:41:32 -06:00
.mailmap A few early MIPS fixes for 4.21: 2019-01-05 12:48:25 -08:00
COPYING COPYING: use the new text with points to the license files 2018-03-23 12:41:45 -06:00
CREDITS CREDITS/MAINTAINERS: Retire parisc-linux.org email domain 2019-02-21 20:16:10 +01:00
Kbuild kbuild: use assignment instead of define ... endef for filechk_* rules 2019-01-06 10:22:35 +09:00
Kconfig kconfig: move the "Executable file formats" menu to fs/Kconfig.binfmt 2018-08-02 08:06:55 +09:00
MAINTAINERS Linux 5.0 2019-03-04 12:02:55 +10:00
Makefile Linux 5.0 2019-03-03 15:21:29 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.