mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-12-27 11:06:41 -05:00
d6d458d42e
Sometimes setting up a DisplayPort tunnel may take quite long time. The reason is that the graphics driver (DPRX) is expected to issue read of certain monitor capabilities over the AUX channel and the "suggested" timeout from VESA is 5 seconds. If there is no graphics driver loaded this does not happen and currently we timeout and tear the tunnel down. The reason for this is that at least Intel discrete USB4 controllers do not send plug/unplug events about whether the DisplayPort cable from the GPU to the controller is connected or not, so in order to "release" the DisplayPort OUT adapter (the one that has monitor connected) we must tear the tunnel down after this timeout has been elapsed. In typical cases there is always graphics driver loaded, and also all the cables are connected but for instance in Intel graphics CI they only load the graphics driver after the system is fully booted up. This makes the driver to tear down the DisplayPort tunnel. To help this case we allow passing bigger or indefinite timeout through a new module parameter (dprx_timeout). To keep the driver bit more responsive during that time we change the way DisplayPort tunnels get activated. We first do the normal tunnel setup and then run the polling of DPRX capabilities read completion in a separate worker. This also makes the driver to accept bandwidth requests to already established DisplayPort tunnels more responsive. If the tunnel still fails to establish we will tear it down and remove the DisplayPort IN adapter from the dp_resource list to avoid using it again (unless we get hotplug to that adapter). Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
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 reStructuredText 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.