137655d1ed
On some panels hooked up to the ti-sn65dsi86 bridge chip we found that link training was failing. Specifically, we'd see: ti_sn65dsi86 2-002d: [drm:ti_sn_bridge_enable] *ERROR* Link training failed, link is off (-5) The panel was hooked up to a logic analyzer and it was found that, as part of link training, the bridge chip was writing a 0x1 to DPCD address 00600h and the panel responded NACK. As can be seen in header files, the write of 0x1 to DPCD address 0x600h means we were trying to write the value DP_SET_POWER_D0 to the register DP_SET_POWER. The panel vendor says that a NACK in this case is not unexpected and means "not ready, try again". In testing, we found that this panel would respond with a NACK in about 1/25 times. Adding the retry logic worked fine and the most number of tries needed was 3. Just to be safe, we'll add 10 tries here and we'll add a little blurb to the logs if we ever need more than 5. Signed-off-by: Douglas Anderson <dianders@chromium.org> Tested-By: Steev Klimaszewski <steev@kali.org> Signed-off-by: Sam Ravnborg <sam@ravnborg.org> Link: https://patchwork.freedesktop.org/patch/msgid/20201002135920.1.I2adbc90b2db127763e2444bd5a4e5bf30e1db8e5@changeid
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.