bcm2835-aux: Add aux interrupt controller

The AUX block has a shared interrupt line with a register indicating
which devices have active IRQs. Expose this as a nested interrupt
controller to avoid sharing problems.

See: #1484
     #1573

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

drivers/clk/bcm/clk-bcm2835-aux.c

@@ -17,17 +17,107 @@
 #include <linux/clk/bcm2835.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/interrupt.h>
+#include <linux/irqdomain.h>
+#include <linux/of_irq.h>
 #include <dt-bindings/clock/bcm2835-aux.h>
 
 #define BCM2835_AUXIRQ		0x00
 #define BCM2835_AUXENB		0x04
 
+#define BCM2835_AUXIRQ_NUM_IRQS  3
+
+#define BCM2835_AUXIRQ_UART_IRQ  0
+#define BCM2835_AUXIRQ_SPI1_IRQ  1
+#define BCM2835_AUXIRQ_SPI2_IRQ  2
+
+#define BCM2835_AUXIRQ_UART_MASK 0x01
+#define BCM2835_AUXIRQ_SPI1_MASK 0x02
+#define BCM2835_AUXIRQ_SPI2_MASK 0x04
+
+#define BCM2835_AUXIRQ_ALL_MASK \
+	(BCM2835_AUXIRQ_UART_MASK | \
+	 BCM2835_AUXIRQ_SPI1_MASK | \
+	 BCM2835_AUXIRQ_SPI2_MASK)
+
+struct auxirq_state {
+	void __iomem      *status;
+	u32                enables;
+	struct irq_domain *domain;
+	struct regmap     *local_regmap;
+};
+
+static struct auxirq_state auxirq __read_mostly;
+
+static irqreturn_t bcm2835_auxirq_handler(int irq, void *dev_id)
+{
+	u32 stat = readl_relaxed(auxirq.status);
+	u32 masked = stat & auxirq.enables;
+
+	if (masked & BCM2835_AUXIRQ_UART_MASK)
+		generic_handle_irq(irq_linear_revmap(auxirq.domain,
+						     BCM2835_AUXIRQ_UART_IRQ));
+
+	if (masked & BCM2835_AUXIRQ_SPI1_MASK)
+		generic_handle_irq(irq_linear_revmap(auxirq.domain,
+						     BCM2835_AUXIRQ_SPI1_IRQ));
+
+	if (masked & BCM2835_AUXIRQ_SPI2_MASK)
+		generic_handle_irq(irq_linear_revmap(auxirq.domain,
+						     BCM2835_AUXIRQ_SPI2_IRQ));
+
+	return (masked & BCM2835_AUXIRQ_ALL_MASK) ? IRQ_HANDLED : IRQ_NONE;
+}
+
+static int bcm2835_auxirq_xlate(struct irq_domain *d,
+				 struct device_node *ctrlr,
+				 const u32 *intspec, unsigned int intsize,
+				 unsigned long *out_hwirq,
+				 unsigned int *out_type)
+{
+	if (WARN_ON(intsize != 1))
+		return -EINVAL;
+
+	if (WARN_ON(intspec[0] >= BCM2835_AUXIRQ_NUM_IRQS))
+		return -EINVAL;
+
+	*out_hwirq = intspec[0];
+	*out_type = IRQ_TYPE_NONE;
+	return 0;
+}
+
+static void bcm2835_auxirq_mask(struct irq_data *data)
+{
+	irq_hw_number_t hwirq = irqd_to_hwirq(data);
+
+	auxirq.enables &= ~(1 << hwirq);
+}
+
+static void bcm2835_auxirq_unmask(struct irq_data *data)
+{
+	irq_hw_number_t hwirq = irqd_to_hwirq(data);
+
+	auxirq.enables |= (1 << hwirq);
+}
+
+static struct irq_chip bcm2835_auxirq_chip = {
+	.name = "bcm2835-auxirq",
+	.irq_mask = bcm2835_auxirq_mask,
+	.irq_unmask = bcm2835_auxirq_unmask,
+};
+
+static const struct irq_domain_ops bcm2835_auxirq_ops = {
+	.xlate = bcm2835_auxirq_xlate//irq_domain_xlate_onecell
+};
+
 static int bcm2835_aux_clk_probe(struct platform_device *pdev)
 {
 	struct device *dev = &pdev->dev;
+	struct device_node *node = dev->of_node;
 	struct clk_hw_onecell_data *onecell;
 	const char *parent;
 	struct clk *parent_clk;
+	int parent_irq;
 	struct resource *res;
 	void __iomem *reg, *gate;
 
@@ -41,6 +131,36 @@ static int bcm2835_aux_clk_probe(struct platform_device *pdev)
 	if (IS_ERR(reg))
 		return PTR_ERR(reg);
 
+	parent_irq = irq_of_parse_and_map(node, 0);
+	if (parent_irq) {
+		int ret;
+		int i;
+
+		/* Manage the AUX irq as well */
+		auxirq.status = reg + BCM2835_AUXIRQ;
+		auxirq.domain = irq_domain_add_linear(node,
+						      BCM2835_AUXIRQ_NUM_IRQS,
+						      &bcm2835_auxirq_ops,
+						      NULL);
+		if (!auxirq.domain)
+			return -ENXIO;
+
+		for (i = 0; i < BCM2835_AUXIRQ_NUM_IRQS; i++) {
+			unsigned int irq = irq_create_mapping(auxirq.domain, i);
+
+			if (irq == 0)
+				return -ENXIO;
+
+			irq_set_chip_and_handler(irq, &bcm2835_auxirq_chip,
+						 handle_level_irq);
+		}
+
+		ret = devm_request_irq(dev, parent_irq, bcm2835_auxirq_handler,
+				       0, "bcm2835-auxirq", NULL);
+		if (ret)
+			return ret;
+	}
+
 	onecell = devm_kmalloc(dev, sizeof(*onecell) + sizeof(*onecell->hws) *
 			       BCM2835_AUX_CLOCK_COUNT, GFP_KERNEL);
 	if (!onecell)