irqchip/irq-pruss-intc: Add logic for handling reserved interrupts

The PRUSS INTC has a fixed number of output interrupt lines that are
connected to a number of processors or other PRUSS instances or other
devices (like DMA) on the SoC. The output interrupt lines 2 through 9
are usually connected to the main Arm host processor and are referred
to as host interrupts 0 through 7 from ARM/MPU perspective.

All of these 8 host interrupts are not always exclusively connected
to the Arm interrupt controller. Some SoCs have some interrupt lines
not connected to the Arm interrupt controller at all, while a few others
have the interrupt lines connected to multiple processors in which they
need to be partitioned as per SoC integration needs. For example, AM437x
and 66AK2G SoCs have 2 PRUSS instances each and have the host interrupt 5
connected to the other PRUSS, while AM335x has host interrupt 0 shared
between MPU and TSC_ADC and host interrupts 6 & 7 shared between MPU and
a DMA controller.

Add logic to the PRUSS INTC driver to ignore both these shared and
invalid interrupts.

Co-developed-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: Suman Anna <s-anna@ti.com>
Signed-off-by: Grzegorz Jaszczyk <grzegorz.jaszczyk@linaro.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>

drivers/irqchip/irq-pruss-intc.c

@@ -484,7 +484,7 @@ static int pruss_intc_probe(struct platform_device *pdev)
 	struct pruss_intc *intc;
 	struct pruss_host_irq_data *host_data;
 	int i, irq, ret;
-	u8 max_system_events;
+	u8 max_system_events, irqs_reserved = 0;
 
 	data = of_device_get_match_data(dev);
 	if (!data)
@@ -504,6 +504,16 @@ static int pruss_intc_probe(struct platform_device *pdev)
 	if (IS_ERR(intc->base))
 		return PTR_ERR(intc->base);
 
+	ret = of_property_read_u8(dev->of_node, "ti,irqs-reserved",
+				  &irqs_reserved);
+
+	/*
+	 * The irqs-reserved is used only for some SoC's therefore not having
+	 * this property is still valid
+	 */
+	if (ret < 0 && ret != -EINVAL)
+		return ret;
+
 	pruss_intc_init(intc);
 
 	mutex_init(&intc->lock);
@@ -514,6 +524,9 @@ static int pruss_intc_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	for (i = 0; i < MAX_NUM_HOST_IRQS; i++) {
+		if (irqs_reserved & BIT(i))
+			continue;
+
 		irq = platform_get_irq_byname(pdev, irq_names[i]);
 		if (irq <= 0) {
 			ret = (irq == 0) ? -EINVAL : irq;
@@ -538,8 +551,11 @@ static int pruss_intc_probe(struct platform_device *pdev)
 	return 0;
 
 fail_irq:
-	while (--i >= 0)
-		irq_set_chained_handler_and_data(intc->irqs[i], NULL, NULL);
+	while (--i >= 0) {
+		if (intc->irqs[i])
+			irq_set_chained_handler_and_data(intc->irqs[i], NULL,
+							 NULL);
+	}
 
 	irq_domain_remove(intc->domain);
 
@@ -553,8 +569,11 @@ static int pruss_intc_remove(struct platform_device *pdev)
 	unsigned int hwirq;
 	int i;
 
-	for (i = 0; i < MAX_NUM_HOST_IRQS; i++)
-		irq_set_chained_handler_and_data(intc->irqs[i], NULL, NULL);
+	for (i = 0; i < MAX_NUM_HOST_IRQS; i++) {
+		if (intc->irqs[i])
+			irq_set_chained_handler_and_data(intc->irqs[i], NULL,
+							 NULL);
+	}
 
 	for (hwirq = 0; hwirq < max_system_events; hwirq++)
 		irq_dispose_mapping(irq_find_mapping(intc->domain, hwirq));