arm64: Add cpuidle context save/restore helpers

As we need to start doing some additional work on all idle
paths, let's introduce a set of macros that will perform
the work related to the GICv3 pseudo-NMI idle entry exit.

Stubs are introduced to 32bit ARM for compatibility.
As these helpers are currently unused, there is no functional
change.

Tested-by: Valentin Schneider <[e-mail]>
Reviewed-by: Lorenzo Pieralisi <[e-mail]>
Signed-off-by: Marc Zyngier <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Will Deacon <[e-mail]>

arch/arm/include/asm/cpuidle.h

···
 
 extern int arm_cpuidle_init(int cpu);
 
+struct arm_cpuidle_irq_context { };
+
+#define arm_cpuidle_save_irq_context(c)		(void)c
+#define arm_cpuidle_restore_irq_context(c)	(void)c
+
 #endif

arch/arm64/include/asm/cpuidle.h

···
 	return -EOPNOTSUPP;
 }
 #endif
+
+#ifdef CONFIG_ARM64_PSEUDO_NMI
+#include <asm/arch_gicv3.h>
+
+struct arm_cpuidle_irq_context {
+	unsigned long pmr;
+	unsigned long daif_bits;
+};
+
+#define arm_cpuidle_save_irq_context(__c)				\
+	do {								\
+		struct arm_cpuidle_irq_context *c = __c;		\
+		if (system_uses_irq_prio_masking()) {			\
+			c->daif_bits = read_sysreg(daif);		\
+			write_sysreg(c->daif_bits | PSR_I_BIT | PSR_F_BIT, \
+				     daif);				\
+			c->pmr = gic_read_pmr();			\
+			gic_write_pmr(GIC_PRIO_IRQON | GIC_PRIO_PSR_I_SET); \
+		}							\
+	} while (0)
+
+#define arm_cpuidle_restore_irq_context(__c)				\
+	do {								\
+		struct arm_cpuidle_irq_context *c = __c;		\
+		if (system_uses_irq_prio_masking()) {			\
+			gic_write_pmr(c->pmr);				\
+			write_sysreg(c->daif_bits, daif);		\
+		}							\
+	} while (0)
+#else
+struct arm_cpuidle_irq_context { };
+
+#define arm_cpuidle_save_irq_context(c)		(void)c
+#define arm_cpuidle_restore_irq_context(c)	(void)c
+#endif
 #endif