[PATCH 3/3] ARM: vfp: Use cpu pm notifiers to save vfp state

Colin Cross
2011-06-13T00:44:20Z

When the cpu is powered down in a low power mode, the vfp
registers may be reset.

This patch uses CPU_PM_ENTER and CPU_PM_EXIT notifiers to save
and restore the cpu's vfp registers.

Signed-off-by: Colin Cross <ccross@android.com>
---
arch/arm/vfp/vfpmodule.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 files changed, 40 insertions(+), 0 deletions(-)

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index f25e7ec..6f08dbe 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -21,6 +21,7 @@
#include <asm/cputype.h>
#include <asm/thread_notify.h>
#include <asm/vfp.h>
+#include <asm/cpu_pm.h>

#include "vfpinstr.h"
#include "vfp.h"
@@ -169,6 +170,44 @@ static struct notifier_block vfp_notifier_block = {
.notifier_call = vfp_notifier,
};

+#ifdef CONFIG_CPU_PM
+static int vfp_cpu_pm_notifier(struct notifier_block *self, unsigned long cmd,
+ void *v)
+{
+ u32 fpexc = fmrx(FPEXC);
+ unsigned int cpu = smp_processor_id();
+
+ switch (cmd) {
+ case CPU_PM_ENTER:
+ if (last_VFP_context[cpu]) {
+ fmxr(FPEXC, fpexc | FPEXC_EN);
+ vfp_save_state(last_VFP_context[cpu], fpexc);
+ /* force a reload when coming back from idle */
+ last_VFP_context[cpu] = NULL;
+ fmxr(FPEXC, fpexc & ~FPEXC_EN);
+ }
+ break;
+ case CPU_PM_ENTER_FAILED:
+ case CPU_PM_EXIT:
+ /* make sure VFP is disabled when leaving idle */
+ fmxr(FPEXC, fpexc & ~FPEXC_EN);
+ break;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block vfp_cpu_pm_notifier_block = {
+ .notifier_call = vfp_cpu_pm_notifier,
+};
+
+static void vfp_cpu_pm_init(void)
+{
+ cpu_pm_register_notifier(&vfp_cpu_pm_notifier_block);
+}
+#else
+static inline void vfp_cpu_pm_init(void) { }
+#endif
+
/*
* Raise a SIGFPE for the current process.
* sicode describes the signal being raised.
@@ -563,6 +602,7 @@ static int __init vfp_init(void)
vfp_vector = vfp_support_entry;

thread_register_notifier(&vfp_notifier_block);
+ vfp_cpu_pm_init();
vfp_pm_init();

/*
--
1.7.4.1