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In order to prepare the GPU for sleeping, we may want to submit commands to it. This is a complicated process that may even require some swapping in from shmemfs, if the GPU was in the wrong state. As such, we need to do this preparation step synchronously before the rest of the system has started to turn off (e.g. swapin fails if scsi is suspended). Fortunately, we are provided with a such a hook, pm_ops.prepare(). v2: Compile cleanup v3: Fewer asserts, fewer problems? v4: Ville pointed out that in some circumstances (such as switching off the overlay) the display code may issue a GPU request. This is unexpected, and will result in us going to sleep with us believing the GPU is still awake (though all user work has been saved). Add a comment to remind our future selves of what trouble brews. Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=106640 Testcase: igt/drv_suspend after igt/gem_tiled_swapping Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> Link: https://patchwork.freedesktop.org/patch/msgid/20180525092629.1456-1-chris@chris-wilson.co.uk Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Reviewed-by: Mika Kuoppala <mika.kuoppala@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.
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.