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Some of the SPR values (HID0, MSR, SPRG0) don't change during the run time of a booted kernel, once they have been initialized. The contents of these SPRs are lost when the CPUs enter deep stop states. So instead saving and restoring SPRs from the kernel, use the stop-api provided by the firmware by which the firmware can restore the contents of these SPRs to their initialized values after wakeup from a deep stop state. Apart from these, program the PSSCR value to that of the deepest stop state via the stop-api. This will be used to indicate to the underlying firmware as to what stop state to put the threads that have been woken up by a special-wakeup. And while we are at programming SPRs via stop-api, ensure that HID1, HID4 and HID5 registers which are only available on POWER8 are not requested to be restored by the firware on POWER9. Signed-off-by: Akshay Adiga <akshay.adiga@linux.vnet.ibm.com> Signed-off-by: Gautham R. Shenoy <ego@linux.vnet.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
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.