arm: mvebu: Add IPI support via doorbells

This patch enhances the IRQ controller driver to add support for
Inter-Processor-Interrupts that are needed to enable SMP support.
Signed-off-by: Yehuda Yitschak <yehuday@marvell.com>
Signed-off-by: Gregory CLEMENT <gregory.clement@free-electrons.com>

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

@@ -6,9 +6,15 @@ Required properties:
 - interrupt-controller: Identifies the node as an interrupt controller.
 - #interrupt-cells: The number of cells to define the interrupts. Should be 1.
   The cell is the IRQ number
+
 - reg: Should contain PMIC registers location and length. First pair
   for the main interrupt registers, second pair for the per-CPU
-  interrupt registers
+  interrupt registers. For this last pair, to be compliant with SMP
+  support, the "virtual" must be use (For the record, these registers
+  automatically map to the interrupt controller registers of the
+  current CPU)
+
+
 
 Example:
 
@@ -18,6 +24,6 @@ Example:
               #address-cells = <1>;
               #size-cells = <1>;
               interrupt-controller;
-              reg = <0xd0020000 0x1000>,
-                    <0xd0021000 0x1000>;
+              reg = <0xd0020a00 0x1d0>,
+                    <0xd0021070 0x58>;
         };

arch/arm/boot/dts/armada-xp.dtsi

@@ -24,7 +24,7 @@ / {
 
 	mpic: interrupt-controller@d0020000 {
 	      reg = <0xd0020a00 0x1d0>,
-		    <0xd0021870 0x58>;
+		    <0xd0021070 0x58>;
 	};
 
 	armada-370-xp-pmsu@d0022000 {

arch/arm/mach-mvebu/armada-370-xp.h

@@ -19,4 +19,11 @@
 #define ARMADA_370_XP_REGS_VIRT_BASE	IOMEM(0xfeb00000)
 #define ARMADA_370_XP_REGS_SIZE		SZ_1M
 
+#ifdef CONFIG_SMP
+#include <linux/cpumask.h>
+
+void armada_mpic_send_doorbell(const struct cpumask *mask, unsigned int irq);
+void armada_xp_mpic_smp_cpu_init(void);
+#endif
+
 #endif /* __MACH_ARMADA_370_XP_H */

arch/arm/mach-mvebu/irq-armada-370-xp.c

@@ -24,6 +24,7 @@
 #include <linux/irqdomain.h>
 #include <asm/mach/arch.h>
 #include <asm/exception.h>
+#include <asm/smp_plat.h>
 
 /* Interrupt Controller Registers Map */
 #define ARMADA_370_XP_INT_SET_MASK_OFFS		(0x48)
@@ -35,6 +36,12 @@
 
 #define ARMADA_370_XP_CPU_INTACK_OFFS		(0x44)
 
+#define ARMADA_370_XP_SW_TRIG_INT_OFFS           (0x4)
+#define ARMADA_370_XP_IN_DRBEL_MSK_OFFS          (0xc)
+#define ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS        (0x8)
+
+#define ACTIVE_DOORBELLS			(8)
+
 static void __iomem *per_cpu_int_base;
 static void __iomem *main_int_base;
 static struct irq_domain *armada_370_xp_mpic_domain;
@@ -51,11 +58,22 @@ static void armada_370_xp_irq_unmask(struct irq_data *d)
 	       per_cpu_int_base + ARMADA_370_XP_INT_CLEAR_MASK_OFFS);
 }
 
+#ifdef CONFIG_SMP
+static int armada_xp_set_affinity(struct irq_data *d,
+				  const struct cpumask *mask_val, bool force)
+{
+	return 0;
+}
+#endif
+
 static struct irq_chip armada_370_xp_irq_chip = {
 	.name		= "armada_370_xp_irq",
 	.irq_mask       = armada_370_xp_irq_mask,
 	.irq_mask_ack   = armada_370_xp_irq_mask,
 	.irq_unmask     = armada_370_xp_irq_unmask,
+#ifdef CONFIG_SMP
+	.irq_set_affinity = armada_xp_set_affinity,
+#endif
 };
 
 static int armada_370_xp_mpic_irq_map(struct irq_domain *h,
@@ -72,6 +90,41 @@ static int armada_370_xp_mpic_irq_map(struct irq_domain *h,
 	return 0;
 }
 
+#ifdef CONFIG_SMP
+void armada_mpic_send_doorbell(const struct cpumask *mask, unsigned int irq)
+{
+	int cpu;
+	unsigned long map = 0;
+
+	/* Convert our logical CPU mask into a physical one. */
+	for_each_cpu(cpu, mask)
+		map |= 1 << cpu_logical_map(cpu);
+
+	/*
+	 * Ensure that stores to Normal memory are visible to the
+	 * other CPUs before issuing the IPI.
+	 */
+	dsb();
+
+	/* submit softirq */
+	writel((map << 8) | irq, main_int_base +
+		ARMADA_370_XP_SW_TRIG_INT_OFFS);
+}
+
+void armada_xp_mpic_smp_cpu_init(void)
+{
+	/* Clear pending IPIs */
+	writel(0, per_cpu_int_base + ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS);
+
+	/* Enable first 8 IPIs */
+	writel((1 << ACTIVE_DOORBELLS) - 1, per_cpu_int_base +
+		ARMADA_370_XP_IN_DRBEL_MSK_OFFS);
+
+	/* Unmask IPI interrupt */
+	writel(0, per_cpu_int_base + ARMADA_370_XP_INT_CLEAR_MASK_OFFS);
+}
+#endif /* CONFIG_SMP */
+
 static struct irq_domain_ops armada_370_xp_mpic_irq_ops = {
 	.map = armada_370_xp_mpic_irq_map,
 	.xlate = irq_domain_xlate_onecell,
@@ -98,6 +151,11 @@ static int __init armada_370_xp_mpic_of_init(struct device_node *node,
 		panic("Unable to add Armada_370_Xp MPIC irq domain (DT)\n");
 
 	irq_set_default_host(armada_370_xp_mpic_domain);
+
+#ifdef CONFIG_SMP
+	armada_xp_mpic_smp_cpu_init();
+#endif
+
 	return 0;
 }
 
@@ -111,14 +169,36 @@ asmlinkage void __exception_irq_entry armada_370_xp_handle_irq(struct pt_regs
 					ARMADA_370_XP_CPU_INTACK_OFFS);
 		irqnr = irqstat & 0x3FF;
 
-		if (irqnr < 1023) {
-			irqnr =
-			    irq_find_mapping(armada_370_xp_mpic_domain, irqnr);
+		if (irqnr > 1022)
+			break;
+
+		if (irqnr >= 8) {
+			irqnr =	irq_find_mapping(armada_370_xp_mpic_domain,
+					irqnr);
 			handle_IRQ(irqnr, regs);
 			continue;
 		}
+#ifdef CONFIG_SMP
+		/* IPI Handling */
+		if (irqnr == 0) {
+			u32 ipimask, ipinr;
+
+			ipimask = readl_relaxed(per_cpu_int_base +
+						ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS)
+				& 0xFF;
+
+			writel(0x0, per_cpu_int_base +
+				ARMADA_370_XP_IN_DRBEL_CAUSE_OFFS);
+
+			/* Handle all pending doorbells */
+			for (ipinr = 0; ipinr < ACTIVE_DOORBELLS; ipinr++) {
+				if (ipimask & (0x1 << ipinr))
+					handle_IPI(ipinr, regs);
+			}
+			continue;
+		}
+#endif
 
-		break;
 	} while (1);
 }