ARM: GIC: Convert GIC library to use the IO relaxed operations

The GIC register accesses today make use of readl()/writel()
which prove to be very expensive when used along with mandatory
barriers. This mandatory barriers also introduces an un-necessary
and expensive l2x0_sync() operation. On Cortex-A9 MP cores, GIC
IO accesses from CPU are direct and doesn't go through L2X0 write
buffer.

A DSB before writel_relaxed() in gic_raise_softirq() is added to be
compliant with the Barrier Litmus document - the mailbox scenario.

Signed-off-by: Santosh Shilimkar <[e-mail]>
Acked-by: Catalin Marinas <[e-mail]>
Cc: Will Deacon <[e-mail]>

arch/arm/common/gic.c

···
 	u32 mask = 1 << (d->irq % 32);
 
 	spin_lock(&irq_controller_lock);
-	writel(mask, gic_dist_base(d) + GIC_DIST_ENABLE_CLEAR + (gic_irq(d) / 32) * 4);
+	writel_relaxed(mask, gic_dist_base(d) + GIC_DIST_ENABLE_CLEAR + (gic_irq(d) / 32) * 4);
 	if (gic_arch_extn.irq_mask)
 		gic_arch_extn.irq_mask(d);
 	spin_unlock(&irq_controller_lock);
···
 	spin_lock(&irq_controller_lock);
 	if (gic_arch_extn.irq_unmask)
 		gic_arch_extn.irq_unmask(d);
-	writel(mask, gic_dist_base(d) + GIC_DIST_ENABLE_SET + (gic_irq(d) / 32) * 4);
+	writel_relaxed(mask, gic_dist_base(d) + GIC_DIST_ENABLE_SET + (gic_irq(d) / 32) * 4);
 	spin_unlock(&irq_controller_lock);
 }
 
···
 		spin_unlock(&irq_controller_lock);
 	}
 
-	writel(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
+	writel_relaxed(gic_irq(d), gic_cpu_base(d) + GIC_CPU_EOI);
 }
 
 static int gic_set_type(struct irq_data *d, unsigned int type)
···
 	if (gic_arch_extn.irq_set_type)
 		gic_arch_extn.irq_set_type(d, type);
 
-	val = readl(base + GIC_DIST_CONFIG + confoff);
+	val = readl_relaxed(base + GIC_DIST_CONFIG + confoff);
 	if (type == IRQ_TYPE_LEVEL_HIGH)
 		val &= ~confmask;
 	else if (type == IRQ_TYPE_EDGE_RISING)
···
 	 * As recommended by the spec, disable the interrupt before changing
 	 * the configuration
 	 */
-	if (readl(base + GIC_DIST_ENABLE_SET + enableoff) & enablemask) {
-		writel(enablemask, base + GIC_DIST_ENABLE_CLEAR + enableoff);
+	if (readl_relaxed(base + GIC_DIST_ENABLE_SET + enableoff) & enablemask) {
+		writel_relaxed(enablemask, base + GIC_DIST_ENABLE_CLEAR + enableoff);
 		enabled = true;
 	}
 
-	writel(val, base + GIC_DIST_CONFIG + confoff);
+	writel_relaxed(val, base + GIC_DIST_CONFIG + confoff);
 
 	if (enabled)
-		writel(enablemask, base + GIC_DIST_ENABLE_SET + enableoff);
+		writel_relaxed(enablemask, base + GIC_DIST_ENABLE_SET + enableoff);
 
 	spin_unlock(&irq_controller_lock);
 
···
 
 	spin_lock(&irq_controller_lock);
 	d->node = cpu;
-	val = readl(reg) & ~mask;
-	writel(val | bit, reg);
+	val = readl_relaxed(reg) & ~mask;
+	writel_relaxed(val | bit, reg);
 	spin_unlock(&irq_controller_lock);
 
 	return 0;
···
 	chained_irq_enter(chip, desc);
 
 	spin_lock(&irq_controller_lock);
-	status = readl(chip_data->cpu_base + GIC_CPU_INTACK);
+	status = readl_relaxed(chip_data->cpu_base + GIC_CPU_INTACK);
 	spin_unlock(&irq_controller_lock);
 
 	gic_irq = (status & 0x3ff);
···
 	cpumask |= cpumask << 8;
 	cpumask |= cpumask << 16;
 
-	writel(0, base + GIC_DIST_CTRL);
+	writel_relaxed(0, base + GIC_DIST_CTRL);
 
 	/*
 	 * Find out how many interrupts are supported.
 	 * The GIC only supports up to 1020 interrupt sources.
 	 */
-	gic_irqs = readl(base + GIC_DIST_CTR) & 0x1f;
+	gic_irqs = readl_relaxed(base + GIC_DIST_CTR) & 0x1f;
 	gic_irqs = (gic_irqs + 1) * 32;
 	if (gic_irqs > 1020)
 		gic_irqs = 1020;
···
 	 * Set all global interrupts to be level triggered, active low.
 	 */
 	for (i = 32; i < gic_irqs; i += 16)
-		writel(0, base + GIC_DIST_CONFIG + i * 4 / 16);
+		writel_relaxed(0, base + GIC_DIST_CONFIG + i * 4 / 16);
 
 	/*
 	 * Set all global interrupts to this CPU only.
 	 */
 	for (i = 32; i < gic_irqs; i += 4)
-		writel(cpumask, base + GIC_DIST_TARGET + i * 4 / 4);
+		writel_relaxed(cpumask, base + GIC_DIST_TARGET + i * 4 / 4);
 
 	/*
 	 * Set priority on all global interrupts.
 	 */
 	for (i = 32; i < gic_irqs; i += 4)
-		writel(0xa0a0a0a0, base + GIC_DIST_PRI + i * 4 / 4);
+		writel_relaxed(0xa0a0a0a0, base + GIC_DIST_PRI + i * 4 / 4);
 
 	/*
 	 * Disable all interrupts.  Leave the PPI and SGIs alone
 	 * as these enables are banked registers.
 	 */
 	for (i = 32; i < gic_irqs; i += 32)
-		writel(0xffffffff, base + GIC_DIST_ENABLE_CLEAR + i * 4 / 32);
+		writel_relaxed(0xffffffff, base + GIC_DIST_ENABLE_CLEAR + i * 4 / 32);
 
 	/*
 	 * Limit number of interrupts registered to the platform maximum
···
 		set_irq_flags(i, IRQF_VALID | IRQF_PROBE);
 	}
 
-	writel(1, base + GIC_DIST_CTRL);
+	writel_relaxed(1, base + GIC_DIST_CTRL);
 }
 
 static void __cpuinit gic_cpu_init(struct gic_chip_data *gic)
···
 	 * Deal with the banked PPI and SGI interrupts - disable all
 	 * PPI interrupts, ensure all SGI interrupts are enabled.
 	 */
-	writel(0xffff0000, dist_base + GIC_DIST_ENABLE_CLEAR);
-	writel(0x0000ffff, dist_base + GIC_DIST_ENABLE_SET);
+	writel_relaxed(0xffff0000, dist_base + GIC_DIST_ENABLE_CLEAR);
+	writel_relaxed(0x0000ffff, dist_base + GIC_DIST_ENABLE_SET);
 
 	/*
 	 * Set priority on PPI and SGI interrupts
 	 */
 	for (i = 0; i < 32; i += 4)
-		writel(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4 / 4);
+		writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4 / 4);
 
-	writel(0xf0, base + GIC_CPU_PRIMASK);
-	writel(1, base + GIC_CPU_CTRL);
+	writel_relaxed(0xf0, base + GIC_CPU_PRIMASK);
+	writel_relaxed(1, base + GIC_CPU_CTRL);
 }
 
 void __init gic_init(unsigned int gic_nr, unsigned int irq_start,
···
 {
 	unsigned long map = *cpus_addr(*mask);
 
+	/*
+	 * Ensure that stores to Normal memory are visible to the
+	 * other CPUs before issuing the IPI.
+	 */
+	dsb();
+
 	/* this always happens on GIC0 */
-	writel(map << 16 | irq, gic_data[0].dist_base + GIC_DIST_SOFTINT);
+	writel_relaxed(map << 16 | irq, gic_data[0].dist_base + GIC_DIST_SOFTINT);
 }
 #endif