[PATCH v3 3/4] irqchip/apple-aic: Add a new "Global fast IPIs only" feature level

[Nick Chan <towinchenmi@gmail.com>]

Starting with the A11 (T8015) SoC, Apple began using arm64 sysregs for
fast IPIs. However, on A11, there is no such things as "Local" fast IPIs,
as the SYS_IMP_APL_IPI_RR_LOCAL_EL1 register does not seem to exist.

Add a new feature level, used by the compatible "apple,t8015-aic",
controlled by a static branch key named use_local_fast_ipi. When
use_fast_ipi is true and use_local_fast_ipi is false, fast IPIs are used
but all IPIs goes through the register SYS_IMP_APL_IPI_RR_GLOBAL_EL1, as
"global" IPIs.

Reviewed-by: Sven Peter <sven@svenpeter.dev>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 drivers/irqchip/irq-apple-aic.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
index 8d81d5fb3c50..01a3c79054f5 100644
--- a/drivers/irqchip/irq-apple-aic.c
+++ b/drivers/irqchip/irq-apple-aic.c
@@ -235,6 +235,8 @@ enum fiq_hwirq {
 };
 
 static DEFINE_STATIC_KEY_TRUE(use_fast_ipi);
+/* True if SYS_IMP_APL_IPI_RR_LOCAL_EL1 exists for local fast IPIs (M1+) */
+static DEFINE_STATIC_KEY_TRUE(use_local_fast_ipi);
 
 struct aic_info {
 	int version;
@@ -252,6 +254,7 @@ struct aic_info {
 
 	/* Features */
 	bool fast_ipi;
+	bool local_fast_ipi;
 };
 
 static const struct aic_info aic1_info __initconst = {
@@ -270,17 +273,32 @@ static const struct aic_info aic1_fipi_info __initconst = {
 	.fast_ipi	= true,
 };
 
+static const struct aic_info aic1_local_fipi_info __initconst = {
+	.version	= 1,
+
+	.event		= AIC_EVENT,
+	.target_cpu	= AIC_TARGET_CPU,
+
+	.fast_ipi	= true,
+	.local_fast_ipi = true,
+};
+
 static const struct aic_info aic2_info __initconst = {
 	.version	= 2,
 
 	.irq_cfg	= AIC2_IRQ_CFG,
 
 	.fast_ipi	= true,
+	.local_fast_ipi = true,
 };
 
 static const struct of_device_id aic_info_match[] = {
 	{
 		.compatible = "apple,t8103-aic",
+		.data = &aic1_local_fipi_info,
+	},
+	{
+		.compatible = "apple,t8015-aic",
 		.data = &aic1_fipi_info,
 	},
 	{
@@ -750,7 +768,8 @@ static void aic_ipi_send_fast(int cpu)
 	u64 cluster = MPIDR_CLUSTER(mpidr);
 	u64 idx = MPIDR_CPU(mpidr);
 
-	if (MPIDR_CLUSTER(my_mpidr) == cluster)
+	if (static_branch_likely(&use_local_fast_ipi) &&
+	    MPIDR_CLUSTER(my_mpidr) == cluster)
 		write_sysreg_s(FIELD_PREP(IPI_RR_CPU, idx),
 			       SYS_IMP_APL_IPI_RR_LOCAL_EL1);
 	else
@@ -990,6 +1009,9 @@ static int __init aic_of_ic_init(struct device_node *node, struct device_node *p
 	if (!irqc->info.fast_ipi)
 		static_branch_disable(&use_fast_ipi);
 
+	if (!irqc->info.local_fast_ipi)
+		static_branch_disable(&use_local_fast_ipi);
+
 	irqc->info.die_stride = off - start_off;
 
 	irqc->hw_domain = irq_domain_create_tree(of_node_to_fwnode(node),
-- 
2.46.0