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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/kernel/suspend.c
parent3f8161b260cb9232bb926a5d6c1cc2672fea07c7 (diff)
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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/kernel/suspend.c')
-rw-r--r--arch/arm64/kernel/suspend.c48
1 files changed, 29 insertions, 19 deletions
diff --git a/arch/arm64/kernel/suspend.c b/arch/arm64/kernel/suspend.c
index 55a99b9a97e0..13ad4dbb1615 100644
--- a/arch/arm64/kernel/suspend.c
+++ b/arch/arm64/kernel/suspend.c
@@ -9,22 +9,19 @@
#include <asm/suspend.h>
#include <asm/tlbflush.h>
-extern int __cpu_suspend(unsigned long);
+extern int __cpu_suspend_enter(unsigned long arg, int (*fn)(unsigned long));
/*
- * This is called by __cpu_suspend() to save the state, and do whatever
+ * This is called by __cpu_suspend_enter() to save the state, and do whatever
* flushing is required to ensure that when the CPU goes to sleep we have
* the necessary data available when the caches are not searched.
*
- * @arg: Argument to pass to suspend operations
- * @ptr: CPU context virtual address
- * @save_ptr: address of the location where the context physical address
- * must be saved
+ * ptr: CPU context virtual address
+ * save_ptr: address of the location where the context physical address
+ * must be saved
*/
-int __cpu_suspend_finisher(unsigned long arg, struct cpu_suspend_ctx *ptr,
- phys_addr_t *save_ptr)
+void notrace __cpu_suspend_save(struct cpu_suspend_ctx *ptr,
+ phys_addr_t *save_ptr)
{
- int cpu = smp_processor_id();
-
*save_ptr = virt_to_phys(ptr);
cpu_do_suspend(ptr);
@@ -35,8 +32,6 @@ int __cpu_suspend_finisher(unsigned long arg, struct cpu_suspend_ctx *ptr,
*/
__flush_dcache_area(ptr, sizeof(*ptr));
__flush_dcache_area(save_ptr, sizeof(*save_ptr));
-
- return cpu_ops[cpu]->cpu_suspend(arg);
}
/*
@@ -56,15 +51,15 @@ void __init cpu_suspend_set_dbg_restorer(void (*hw_bp_restore)(void *))
}
/**
- * cpu_suspend
+ * cpu_suspend() - function to enter a low-power state
+ * @arg: argument to pass to CPU suspend operations
*
- * @arg: argument to pass to the finisher function
+ * Return: 0 on success, -EOPNOTSUPP if CPU suspend hook not initialized, CPU
+ * operations back-end error code otherwise.
*/
int cpu_suspend(unsigned long arg)
{
- struct mm_struct *mm = current->active_mm;
- int ret, cpu = smp_processor_id();
- unsigned long flags;
+ int cpu = smp_processor_id();
/*
* If cpu_ops have not been registered or suspend
@@ -72,6 +67,21 @@ int cpu_suspend(unsigned long arg)
*/
if (!cpu_ops[cpu] || !cpu_ops[cpu]->cpu_suspend)
return -EOPNOTSUPP;
+ return cpu_ops[cpu]->cpu_suspend(arg);
+}
+
+/*
+ * __cpu_suspend
+ *
+ * arg: argument to pass to the finisher function
+ * fn: finisher function pointer
+ *
+ */
+int __cpu_suspend(unsigned long arg, int (*fn)(unsigned long))
+{
+ struct mm_struct *mm = current->active_mm;
+ int ret;
+ unsigned long flags;
/*
* From this point debug exceptions are disabled to prevent
@@ -86,7 +96,7 @@ int cpu_suspend(unsigned long arg)
* page tables, so that the thread address space is properly
* set-up on function return.
*/
- ret = __cpu_suspend(arg);
+ ret = __cpu_suspend_enter(arg, fn);
if (ret == 0) {
cpu_switch_mm(mm->pgd, mm);
flush_tlb_all();
@@ -95,7 +105,7 @@ int cpu_suspend(unsigned long arg)
* Restore per-cpu offset before any kernel
* subsystem relying on it has a chance to run.
*/
- set_my_cpu_offset(per_cpu_offset(cpu));
+ set_my_cpu_offset(per_cpu_offset(smp_processor_id()));
/*
* Restore HW breakpoint registers to sane values