[PATCH v3 4/4] irqchip/apple-aic: Only access system registers on SoCs which provide them

[Nick Chan <towinchenmi@gmail.com>]

From: Konrad Dybcio <konrad.dybcio@somainline.org>

Starting from the A11 (T8015) SoC, Apple introuced system registers for
fast IPI and UNCORE PMC control. These sysregs do not exist on earlier
A7-A10 SoCs and trying to access them results in an instant crash.

Restrict sysreg access within the AIC driver to configurations where
use_fast_ipi is true to allow AIC to function properly on A7-A10 SoCs.

Reviewed-by: Sven Peter <sven@svenpeter.dev>
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Co-developed-by: Nick Chan <towinchenmi@gmail.com>
Signed-off-by: Nick Chan <towinchenmi@gmail.com>
---
 drivers/irqchip/irq-apple-aic.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/drivers/irqchip/irq-apple-aic.c b/drivers/irqchip/irq-apple-aic.c
index 01a3c79054f5..a6d812afb10d 100644
--- a/drivers/irqchip/irq-apple-aic.c
+++ b/drivers/irqchip/irq-apple-aic.c
@@ -234,6 +234,7 @@ enum fiq_hwirq {
 	AIC_NR_FIQ
 };
 
+/* True if UNCORE/UNCORE2 and Sn_... IPI registers are present and used (A11+) */
 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);
@@ -550,14 +551,9 @@ static void __exception_irq_entry aic_handle_fiq(struct pt_regs *regs)
 	 * we check for everything here, even things we don't support yet.
 	 */
 
-	if (read_sysreg_s(SYS_IMP_APL_IPI_SR_EL1) & IPI_SR_PENDING) {
-		if (static_branch_likely(&use_fast_ipi)) {
-			aic_handle_ipi(regs);
-		} else {
-			pr_err_ratelimited("Fast IPI fired. Acking.\n");
-			write_sysreg_s(IPI_SR_PENDING, SYS_IMP_APL_IPI_SR_EL1);
-		}
-	}
+	if (static_branch_likely(&use_fast_ipi) &&
+	    (read_sysreg_s(SYS_IMP_APL_IPI_SR_EL1) & IPI_SR_PENDING))
+		aic_handle_ipi(regs);
 
 	if (TIMER_FIRING(read_sysreg(cntp_ctl_el0)))
 		generic_handle_domain_irq(aic_irqc->hw_domain,
@@ -592,8 +588,9 @@ static void __exception_irq_entry aic_handle_fiq(struct pt_regs *regs)
 					  AIC_FIQ_HWIRQ(irq));
 	}
 
-	if (FIELD_GET(UPMCR0_IMODE, read_sysreg_s(SYS_IMP_APL_UPMCR0_EL1)) == UPMCR0_IMODE_FIQ &&
-			(read_sysreg_s(SYS_IMP_APL_UPMSR_EL1) & UPMSR_IACT)) {
+	if (static_branch_likely(&use_fast_ipi) &&
+	    (FIELD_GET(UPMCR0_IMODE, read_sysreg_s(SYS_IMP_APL_UPMCR0_EL1)) == UPMCR0_IMODE_FIQ) &&
+	    (read_sysreg_s(SYS_IMP_APL_UPMSR_EL1) & UPMSR_IACT)) {
 		/* Same story with uncore PMCs */
 		pr_err_ratelimited("Uncore PMC FIQ fired. Masking.\n");
 		sysreg_clear_set_s(SYS_IMP_APL_UPMCR0_EL1, UPMCR0_IMODE,
@@ -830,7 +827,8 @@ static int aic_init_cpu(unsigned int cpu)
 	/* Mask all hard-wired per-CPU IRQ/FIQ sources */
 
 	/* Pending Fast IPI FIQs */
-	write_sysreg_s(IPI_SR_PENDING, SYS_IMP_APL_IPI_SR_EL1);
+	if (static_branch_likely(&use_fast_ipi))
+		write_sysreg_s(IPI_SR_PENDING, SYS_IMP_APL_IPI_SR_EL1);
 
 	/* Timer FIQs */
 	sysreg_clear_set(cntp_ctl_el0, 0, ARCH_TIMER_CTRL_IT_MASK);
@@ -851,8 +849,9 @@ static int aic_init_cpu(unsigned int cpu)
 			   FIELD_PREP(PMCR0_IMODE, PMCR0_IMODE_OFF));
 
 	/* Uncore PMC FIQ */
-	sysreg_clear_set_s(SYS_IMP_APL_UPMCR0_EL1, UPMCR0_IMODE,
-			   FIELD_PREP(UPMCR0_IMODE, UPMCR0_IMODE_OFF));
+	if (static_branch_likely(&use_fast_ipi))
+		sysreg_clear_set_s(SYS_IMP_APL_UPMCR0_EL1, UPMCR0_IMODE,
+				   FIELD_PREP(UPMCR0_IMODE, UPMCR0_IMODE_OFF));
 
 	/* Commit all of the above */
 	isb();
-- 
2.46.0