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We would like to reset the Group-0 Active Priority Registers at boot time if they are available to us. They would be available if SCR_EL3.FIQ was not set, but we cannot directly probe this bit, and short of checking, we may end-up trapping to EL3, and the firmware may not be please to get such an exception. Yes, this is dumb. Instead, let's use PMR to find out if its value gets affected by SCR_EL3.FIQ being set. We use the fact that when SCR_EL3.FIQ is set, the LSB of the priority is lost due to the shifting back and forth of the actual priority. If we read back a 0, we know that Group0 is unavailable. In case we read a non-zero value, we can safely reset the AP0Rn register. Signed-off-by: Marc Zyngier <marc.zyngier@arm.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.