mainlining shenanigans
90024a5951
The ACK/NACK implementation as found in e.g. the G965 has the falling
clock edge and the release of the data line after the ACK for the received
byte happen at the same time.
This is conformant with the I2C specification, which allows a zero hold
time, see footnote [3]: "A device must internally provide a hold time of
at least 300 ns for the SDA signal (with respect to the V IH(min) of the
SCL signal) to bridge the undefined region of the falling edge of SCL."
Some HDMI-to-VGA converters apparently fail to adhere to this requirement
and latch SDA at the falling clock edge, so instead of an ACK
sometimes a NACK is read and the slave (i.e. the EDID ROM) ends the
transfer.
The bitbanging releases the data line for the ACK only 1/4 bit time after
the falling clock edge, so a slave will see the correct value no matter
if it samples at the rising or the falling clock edge or in the center.
Fallback to bitbanging is already done for the CRT connector.
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=92685
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/a39f080b-81a5-4c93-b3f7-7cb0a58daca3@rwthex-w2-a.rwth-ad.de
(cherry picked from commit
|
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| firmware | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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.