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Commit fb1ab1ab authored by Lorenzo Pieralisi's avatar Lorenzo Pieralisi
Browse files

arm64: kernel: implement fpsimd CPU PM notifier 



When a CPU enters a low power state, its FP register content is lost.
This patch adds a notifier to save the FP context on CPU shutdown
and restore it on CPU resume. The context is saved and restored only
if the suspending thread is not a kernel thread, mirroring the current
context switch behaviour.

Signed-off-by: default avatarLorenzo Pieralisi <lorenzo.pieralisi@arm.com>
parent 95322526

arch/arm64/kernel/fpsimd.c

+36 −0
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.

 */



#include <linux/cpu_pm.h>

#include <linux/kernel.h>

#include <linux/init.h>

#include <linux/sched.h>
@@ -113,6 +114,39 @@ EXPORT_SYMBOL(kernel_neon_end); 


#endif /* CONFIG_KERNEL_MODE_NEON */



#ifdef CONFIG_CPU_PM

static int fpsimd_cpu_pm_notifier(struct notifier_block *self,

				  unsigned long cmd, void *v)

{

	switch (cmd) {

	case CPU_PM_ENTER:

		if (current->mm)

			fpsimd_save_state(&current->thread.fpsimd_state);

		break;

	case CPU_PM_EXIT:

		if (current->mm)

			fpsimd_load_state(&current->thread.fpsimd_state);

		break;

	case CPU_PM_ENTER_FAILED:

	default:

		return NOTIFY_DONE;

	}

	return NOTIFY_OK;

}



static struct notifier_block fpsimd_cpu_pm_notifier_block = {

	.notifier_call = fpsimd_cpu_pm_notifier,

};



static void fpsimd_pm_init(void)

{

	cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block);

}



#else

static inline void fpsimd_pm_init(void) { }

#endif /* CONFIG_CPU_PM */



/*

 * FP/SIMD support code initialisation.

 */
@@ -131,6 +165,8 @@ static int __init fpsimd_init(void) 
	else

		elf_hwcap |= HWCAP_ASIMD;



	fpsimd_pm_init();



	return 0;

}

late_initcall(fpsimd_init);