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If protocol tunnels are already up when the driver is loaded, for instance if the boot firmware implements connection manager of its own, runtime PM reference count of the consumer devices behind the tunnel might have been increased already before the device link is created but the supplier device runtime PM reference count is not. This leads to a situation where the supplier (the Thunderbolt driver) can runtime suspend even if it should not because the corresponding protocol tunnel needs to be up causing the devices to be removed from the corresponding native bus. Prevent this from happening by making both sides of the link runtime PM active briefly. The pm_runtime_put() for the consumer (PCIe root/downstream port, xHCI) then allows it to runtime suspend again but keeps the supplier runtime resumed the whole time it is runtime active. Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@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 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.