arm64: Convert cpu_do_idle() to using cpuidle context helpers

Now that we have helpers that are aware of the pseudo-NMI
feature, introduce them to cpu_do_idle(). This allows for
some nice cleanup.

No functional change intended.

Tested-by: Valentin Schneider <valentin.schneider@arm.com>
Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20210615111227.2454465-3-maz@kernel.org
Signed-off-by: Will Deacon <will@kernel.org>

Author: Marc Zyngier

arch/arm64/kernel/process.c

@@ -46,9 +46,9 @@
 #include <linux/prctl.h>
 
 #include <asm/alternative.h>
-#include <asm/arch_gicv3.h>
 #include <asm/compat.h>
 #include <asm/cpufeature.h>
+#include <asm/cpuidle.h>
 #include <asm/cacheflush.h>
 #include <asm/exec.h>
 #include <asm/fpsimd.h>
@@ -74,33 +74,6 @@ EXPORT_SYMBOL_GPL(pm_power_off);
 
 void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
 
-static void noinstr __cpu_do_idle(void)
-{
-	dsb(sy);
-	wfi();
-}
-
-static void noinstr __cpu_do_idle_irqprio(void)
-{
-	unsigned long pmr;
-	unsigned long daif_bits;
-
-	daif_bits = read_sysreg(daif);
-	write_sysreg(daif_bits | PSR_I_BIT | PSR_F_BIT, daif);
-
-	/*
-	 * Unmask PMR before going idle to make sure interrupts can
-	 * be raised.
-	 */
-	pmr = gic_read_pmr();
-	gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET);
-
-	__cpu_do_idle();
-
-	gic_write_pmr(pmr);
-	write_sysreg(daif_bits, daif);
-}
-
 /*
  *	cpu_do_idle()
  *
@@ -112,10 +85,14 @@ static void noinstr __cpu_do_idle_irqprio(void)
  */
 void noinstr cpu_do_idle(void)
 {
-	if (system_uses_irq_prio_masking())
-		__cpu_do_idle_irqprio();
-	else
-		__cpu_do_idle();
+	struct arm_cpuidle_irq_context context;
+
+	arm_cpuidle_save_irq_context(&context);
+
+	dsb(sy);
+	wfi();
+
+	arm_cpuidle_restore_irq_context(&context);
 }
 
 /*