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commit aa86f1a388 upstream.
The tmio_mmc_host_probe() calls pm_runtime_set_active() to update the
runtime PM status of the device, as to make it reflect the current status
of the HW. This works fine for most cases, but unfortunate not for all.
Especially, there is a generic problem when the device has a genpd attached
and that genpd have the ->start|stop() callbacks assigned.
More precisely, if the driver calls pm_runtime_set_active() during
->probe(), genpd does not get to invoke the ->start() callback for it,
which means the HW isn't really fully powered on. Furthermore, in the next
phase, when the device becomes runtime suspended, genpd will invoke the
->stop() callback for it, potentially leading to usage count imbalance
problems, depending on what's implemented behind the callbacks of course.
To fix this problem, convert to call pm_runtime_get_sync() from
tmio_mmc_host_probe() rather than pm_runtime_set_active(). Additionally, to
avoid bumping usage counters and unnecessary re-initializing the HW the
first time the tmio driver's ->runtime_resume() callback is called,
introduce a state flag to keeping track of this.
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Tested-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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.