Subject: [PATCH RFC 2/2] irqchip/gic: Allow the use of SGI interrupts

From: Florian Fainelli <[email-masked]>
Date: Tue, 22 Oct 2019 17:05:47 -0700

SGI interrupts are a convenient way for trusted firmware to target a
specific set of CPUs. Update the ARM GIC code to allow the translation
and mapping of SGI interrupts.

Since the kernel already uses SGIs for various inter-processor interrupt
activities, we specifically make sure that we do not let users of the
IRQ API to even try to map those.

Internal IPIs remain dispatched through handle_IPI() while public SGIs
get promoted to a normal interrupt flow management.

Signed-off-by: Florian Fainelli <[email-masked]>
---
 drivers/irqchip/irq-gic.c | 41 +++++++++++++++++++++++++++------------
 1 file changed, 29 insertions(+), 12 deletions(-)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index 30ab623343d3..dcfdbaacdd64 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -385,7 +385,10 @@ static void __exception_irq_entry gic_handle_irq(struct pt_regs *regs)
 			 * Pairs with the write barrier in gic_raise_softirq
 			 */
 			smp_rmb();
-			handle_IPI(irqnr, regs);
+			if (irqnr < NR_IPI)
+				handle_IPI(irqnr, regs);
+			else
+				handle_domain_irq(gic->domain, irqnr, regs);
 #endif
 			continue;
 		}
@@ -1005,20 +1008,34 @@ static int gic_irq_domain_translate(struct irq_domain *d,
 		if (fwspec->param_count < 3)
 			return -EINVAL;
 
-		/* Get the interrupt number and add 16 to skip over SGIs */
-		*hwirq = fwspec->param[1] + 16;
-
-		/*
-		 * For SPIs, we need to add 16 more to get the GIC irq
-		 * ID number
-		 */
-		if (!fwspec->param[0])
+		*hwirq = fwspec->param[1];
+		switch (fwspec->param[0]) {
+		case 0:
+			/*
+			 * For SPIs, we need to add 16 more to get the GIC irq
+			 * ID number
+			 */
+			*hwirq += 16;
+			/* fall through */
+		case 1:
+			/* Add 16 to skip over SGIs */
 			*hwirq += 16;
+			*type = fwspec->param[2] & IRQ_TYPE_SENSE_MASK;
 
-		*type = fwspec->param[2] & IRQ_TYPE_SENSE_MASK;
+			/* Make it clear that broken DTs are... broken */
+			WARN_ON(*type == IRQ_TYPE_NONE);
+			break;
+		case 2:
+			/* Refuse to map internal IPIs */
+			if (*hwirq < NR_IPI)
+				return -EPERM;
+
+			*type = IRQ_TYPE_NONE;
+			break;
+		default:
+			break;
+		}
 
-		/* Make it clear that broken DTs are... broken */
-		WARN_ON(*type == IRQ_TYPE_NONE);
 		return 0;
 	}
 
-- 
2.17.1

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