irqchip: armada-370-xp: implement MSI support

This commit introduces the support for the MSI interrupts in the
armada-370-xp interrupt controller driver. It registers an MSI chip to
the MSI chip registry, which will be used by the Marvell PCIe host
controller driver.

The MSI interrupts use the 16 high doorbells, and are therefore
notified using IRQ1 of the main interrupt controller.

Signed-off-by: Thomas Petazzoni <[e-mail]>
Acked-by: Gregory CLEMENT <[e-mail]>
Signed-off-by: Jason Cooper <[e-mail]>

Documentation/devicetree/bindings/arm/armada-370-xp-mpic.txt

···
 Required properties:
 - compatible: Should be "marvell,mpic"
 - interrupt-controller: Identifies the node as an interrupt controller.
+- msi-controller: Identifies the node as an PCI Message Signaled
+  Interrupt controller.
 - #interrupt-cells: The number of cells to define the interrupts. Should be 1.
   The cell is the IRQ number
 
···
               #address-cells = <1>;
               #size-cells = <1>;
               interrupt-controller;
+              msi-controller;
               reg = <0xd0020a00 0x1d0>,
                     <0xd0021070 0x58>;
         };

drivers/irqchip/irq-armada-370-xp.c

···
 #include <linux/io.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#include <linux/of_pci.h>
 #include <linux/irqdomain.h>
+#include <linux/slab.h>
+#include <linux/msi.h>
 #include <asm/mach/arch.h>
 #include <asm/exception.h>
 #include <asm/smp_plat.h>
···
 #define IPI_DOORBELL_START                      (0)
 #define IPI_DOORBELL_END                        (8)
 #define IPI_DOORBELL_MASK                       0xFF
+#define PCI_MSI_DOORBELL_START                  (16)
+#define PCI_MSI_DOORBELL_NR                     (16)
+#define PCI_MSI_DOORBELL_END                    (32)
+#define PCI_MSI_DOORBELL_MASK                   0xFFFF0000
 
 static DEFINE_RAW_SPINLOCK(irq_controller_lock);
 
 static void __iomem *per_cpu_int_base;
 static void __iomem *main_int_base;
 static struct irq_domain *armada_370_xp_mpic_domain;
+#ifdef CONFIG_PCI_MSI
+static struct irq_domain *armada_370_xp_msi_domain;
+static DECLARE_BITMAP(msi_used, PCI_MSI_DOORBELL_NR);
+static DEFINE_MUTEX(msi_used_lock);
+static phys_addr_t msi_doorbell_addr;
+#endif
 
 /*
  * In SMP mode:
···
 		writel(hwirq, per_cpu_int_base +
 				ARMADA_370_XP_INT_CLEAR_MASK_OFFS);
 }
+
+#ifdef CONFIG_PCI_MSI
+
+static int armada_370_xp_alloc_msi(void)
+{
+	int hwirq;
+
+	mutex_lock(&msi_used_lock);
+	hwirq = find_first_zero_bit(&msi_used, PCI_MSI_DOORBELL_NR);
+	if (hwirq >= PCI_MSI_DOORBELL_NR)
+		hwirq = -ENOSPC;
+	else
+		set_bit(hwirq, msi_used);
+	mutex_unlock(&msi_used_lock);
+
+	return hwirq;
+}
+
+static void armada_370_xp_free_msi(int hwirq)
+{
+	mutex_lock(&msi_used_lock);
+	if (!test_bit(hwirq, msi_used))
+		pr_err("trying to free unused MSI#%d\n", hwirq);
+	else
+		clear_bit(hwirq, msi_used);
+	mutex_unlock(&msi_used_lock);
+}
+
+static int armada_370_xp_setup_msi_irq(struct msi_chip *chip,
+				       struct pci_dev *pdev,
+				       struct msi_desc *desc)
+{
+	struct msi_msg msg;
+	irq_hw_number_t hwirq;
+	int virq;
+
+	hwirq = armada_370_xp_alloc_msi();
+	if (hwirq < 0)
+		return hwirq;
+
+	virq = irq_create_mapping(armada_370_xp_msi_domain, hwirq);
+	if (!virq) {
+		armada_370_xp_free_msi(hwirq);
+		return -EINVAL;
+	}
+
+	irq_set_msi_desc(virq, desc);
+
+	msg.address_lo = msi_doorbell_addr;
+	msg.address_hi = 0;
+	msg.data = 0xf00 | (hwirq + 16);
+
+	write_msi_msg(virq, &msg);
+	return 0;
+}
+
+static void armada_370_xp_teardown_msi_irq(struct msi_chip *chip,
+					   unsigned int irq)
+{
+	struct irq_data *d = irq_get_irq_data(irq);
+	irq_dispose_mapping(irq);
+	armada_370_xp_free_msi(d->hwirq);
+}
+
+static struct irq_chip armada_370_xp_msi_irq_chip = {
+	.name = "armada_370_xp_msi_irq",
+	.irq_enable = unmask_msi_irq,
+	.irq_disable = mask_msi_irq,
+	.irq_mask = mask_msi_irq,
+	.irq_unmask = unmask_msi_irq,
+};
+
+static int armada_370_xp_msi_map(struct irq_domain *domain, unsigned int virq,
+				 irq_hw_number_t hw)
+{
+	irq_set_chip_and_handler(virq, &armada_370_xp_msi_irq_chip,
+				 handle_simple_irq);
+	set_irq_flags(virq, IRQF_VALID);
+
+	return 0;
+}
+
+static const struct irq_domain_ops armada_370_xp_msi_irq_ops = {
+	.map = armada_370_xp_msi_map,
+};
+
+static int armada_370_xp_msi_init(struct device_node *node,
+				  phys_addr_t main_int_phys_base)
+{
+	struct msi_chip *msi_chip;
+	u32 reg;
+	int ret;
+
+	msi_doorbell_addr = main_int_phys_base +
+		ARMADA_370_XP_SW_TRIG_INT_OFFS;
+
+	msi_chip = kzalloc(sizeof(*msi_chip), GFP_KERNEL);
+	if (!msi_chip)
+		return -ENOMEM;
+
+	msi_chip->setup_irq = armada_370_xp_setup_msi_irq;
+	msi_chip->teardown_irq = armada_370_xp_teardown_msi_irq;
+	msi_chip->of_node = node;
+
+	armada_370_xp_msi_domain =
+		irq_domain_add_linear(NULL, PCI_MSI_DOORBELL_NR,
+				      &armada_370_xp_msi_irq_ops,
+				      NULL);
+	if (!armada_370_xp_msi_domain) {
+		kfree(msi_chip);
+		return -ENOMEM;
+	}
+
+	ret = of_pci_msi_chip_add(msi_chip);
+	if (ret < 0) {
+		irq_domain_remove(armada_370_xp_msi_domain);
+		kfree(msi_chip);
+		return ret;
+	}
+
+	reg = readl(per_cpu_int_base + ARMADA_370_XP_IN_DRBEL_MSK_OFFS)
+		| PCI_MSI_DOORBELL_MASK;
+
+	writel(reg, per_cpu_int_base +
+	       ARMADA_370_XP_IN_DRBEL_MSK_OFFS);
+
+	/* Unmask IPI interrupt */
+	writel(1, per_cpu_int_base + ARMADA_370_XP_INT_CLEAR_MASK_OFFS);
+
+	return 0;
+}
+#else
+static inline int armada_370_xp_msi_init(struct device_node *node,
+					 phys_addr_t main_int_phys_base)
+{
+	return 0;
+}
+#endif
 
 #ifdef CONFIG_SMP
 static int armada_xp_set_affinity(struct irq_data *d,
···
 		if (irqnr > 1022)
 			break;
 
-		if (irqnr > 0) {
+		if (irqnr > 1) {
 			irqnr =	irq_find_mapping(armada_370_xp_mpic_domain,
 					irqnr);
 			handle_IRQ(irqnr, regs);
 			continue;
 		}
+
+#ifdef CONFIG_PCI_MSI
+		/* MSI handling */
+		if (irqnr == 1) {
+			u32 msimask, msinr;
+
+			msimask = readl_relaxed(per_cpu_int_base +
+						ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS)
+				& PCI_MSI_DOORBELL_MASK;
+
+			writel(~PCI_MSI_DOORBELL_MASK, per_cpu_int_base +
+			       ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS);
+
+			for (msinr = PCI_MSI_DOORBELL_START;
+			     msinr < PCI_MSI_DOORBELL_END; msinr++) {
+				int irq;
+
+				if (!(msimask & BIT(msinr)))
+					continue;
+
+				irq = irq_find_mapping(armada_370_xp_msi_domain,
+						       msinr - 16);
+				handle_IRQ(irq, regs);
+			}
+		}
+#endif
+
 #ifdef CONFIG_SMP
 		/* IPI Handling */
 		if (irqnr == 0) {
···
 	cpumask_set_cpu(smp_processor_id(), irq_default_affinity);
 
 #endif
+
+	armada_370_xp_msi_init(node, main_int_res.start);
 
 	set_handle_irq(armada_370_xp_handle_irq);