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authorLorenzo Pieralisi <lorenzo.pieralisi@arm.com>2014-08-07 14:54:50 +0100
committerCatalin Marinas <catalin.marinas@arm.com>2014-09-12 10:48:55 +0100
commit714f59925595b9c2ea9c22b107b340d38e3b3bc9 (patch)
tree58bc72f8fe0d4bf979e9a712a40cdfe2a89b8c5b /arch/arm64/include/asm/suspend.h
parent3f8161b260cb9232bb926a5d6c1cc2672fea07c7 (diff)
downloadlinux-714f59925595b9c2ea9c22b107b340d38e3b3bc9.tar.bz2
arm64: kernel: refactor the CPU suspend API for retention states
CPU suspend is the standard kernel interface to be used to enter low-power states on ARM64 systems. Current cpu_suspend implementation by default assumes that all low power states are losing the CPU context, so the CPU registers must be saved and cleaned to DRAM upon state entry. Furthermore, the current cpu_suspend() implementation assumes that if the CPU suspend back-end method returns when called, this has to be considered an error regardless of the return code (which can be successful) since the CPU was not expected to return from a code path that is different from cpu_resume code path - eg returning from the reset vector. All in all this means that the current API does not cope well with low-power states that preserve the CPU context when entered (ie retention states), since first of all the context is saved for nothing on state entry for those states and a successful state entry can return as a normal function return, which is considered an error by the current CPU suspend implementation. This patch refactors the cpu_suspend() API so that it can be split in two separate functionalities. The arm64 cpu_suspend API just provides a wrapper around CPU suspend operation hook. A new function is introduced (for architecture code use only) for states that require context saving upon entry: __cpu_suspend(unsigned long arg, int (*fn)(unsigned long)) __cpu_suspend() saves the context on function entry and calls the so called suspend finisher (ie fn) to complete the suspend operation. The finisher is not expected to return, unless it fails in which case the error is propagated back to the __cpu_suspend caller. The API refactoring results in the following pseudo code call sequence for a suspending CPU, when triggered from a kernel subsystem: /* * int cpu_suspend(unsigned long idx) * @idx: idle state index */ { -> cpu_suspend(idx) |---> CPU operations suspend hook called, if present |--> if (retention_state) |--> direct suspend back-end call (eg PSCI suspend) else |--> __cpu_suspend(idx, &back_end_finisher); } By refactoring the cpu_suspend API this way, the CPU operations back-end has a chance to detect whether idle states require state saving or not and can call the required suspend operations accordingly either through simple function call or indirectly through __cpu_suspend() which carries out state saving and suspend finisher dispatching to complete idle state entry. Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Reviewed-by: Hanjun Guo <hanjun.guo@linaro.org> Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/include/asm/suspend.h')
-rw-r--r--arch/arm64/include/asm/suspend.h1
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/suspend.h b/arch/arm64/include/asm/suspend.h
index e9c149c042e0..456d67c1f0fa 100644
--- a/arch/arm64/include/asm/suspend.h
+++ b/arch/arm64/include/asm/suspend.h
@@ -21,6 +21,7 @@ struct sleep_save_sp {
phys_addr_t save_ptr_stash_phys;
};
+extern int __cpu_suspend(unsigned long arg, int (*fn)(unsigned long));
extern void cpu_resume(void);
extern int cpu_suspend(unsigned long);