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One some systems the P-Unit accesses the PMIC to change various voltages through the same bus as other kernel drivers use for e.g. battery monitoring. If a driver sends requests to the P-Unit which require the P-Unit to access the PMIC bus while another driver is also accessing the PMIC bus various bad things happen. This commit adds a mutex to protect the P-Unit against simultaneous accesses and 2 functions to lock / unlock this mutex. Note on these systems the i2c-bus driver will request a sempahore from the P-Unit for exclusive access to the PMIC bus when i2c drivers are accessing it, but this does not appear to be sufficient, we still need to avoid making certain P-Unit requests during the access window to avoid problems. BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=155241 Signed-off-by: Hans de Goede <hdegoede@redhat.com> Tested-by: tagorereddy <tagore.chandan@gmail.com> Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch> Link: http://patchwork.freedesktop.org/patch/msgid/20170210102802.20898-2-hdegoede@redhat.com
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. 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.