irqchip: gic: Preserve gic V2 bypass bits in cpu ctrl register

This change is made to preserve the GIC v2 bypass bits in the
GIC_CPU_CTRL register (also known as the GICC_CTLR register in spec).
This code will preserve all bits configured by the bootloader regarding
v2 bypass group bits. In the X-Gene platform, the bypass functionality
is not used and bypass bits should not be changed by the kernel gic
code as it could lead to incorrect behavior.

Signed-off-by: Feng Kan <fkan@apm.com>
Reviewed-by: Vinayak Kale <vkale@apm.com>
Reviewed-by: Anup Patel <apatel@apm.com>
Link: https://lkml.kernel.org/r/1406757419-18729-3-git-send-email-fkan@apm.com
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

drivers/irqchip/irq-gic.c

@@ -353,6 +353,21 @@ static u8 gic_get_cpumask(struct gic_chip_data *gic)
 	return mask;
 }
 
+static void gic_cpu_if_up(void)
+{
+	void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
+	u32 bypass = 0;
+
+	/*
+	* Preserve bypass disable bits to be written back later
+	*/
+	bypass = readl(cpu_base + GIC_CPU_CTRL);
+	bypass &= GICC_DIS_BYPASS_MASK;
+
+	writel_relaxed(bypass | GICC_ENABLE, cpu_base + GIC_CPU_CTRL);
+}
+
+
 static void __init gic_dist_init(struct gic_chip_data *gic)
 {
 	unsigned int i;
@@ -401,13 +416,17 @@ static void gic_cpu_init(struct gic_chip_data *gic)
 	gic_cpu_config(dist_base, NULL);
 
 	writel_relaxed(GICC_INT_PRI_THRESHOLD, base + GIC_CPU_PRIMASK);
-	writel_relaxed(GICC_ENABLE, base + GIC_CPU_CTRL);
+	gic_cpu_if_up();
 }
 
 void gic_cpu_if_down(void)
 {
 	void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
-	writel_relaxed(0, cpu_base + GIC_CPU_CTRL);
+	u32 val = 0;
+
+	val = readl(cpu_base + GIC_CPU_CTRL);
+	val &= ~GICC_ENABLE;
+	writel_relaxed(val, cpu_base + GIC_CPU_CTRL);
 }
 
 #ifdef CONFIG_CPU_PM
@@ -543,7 +562,7 @@ static void gic_cpu_restore(unsigned int gic_nr)
 					dist_base + GIC_DIST_PRI + i * 4);
 
 	writel_relaxed(GICC_INT_PRI_THRESHOLD, cpu_base + GIC_CPU_PRIMASK);
-	writel_relaxed(GICC_ENABLE, cpu_base + GIC_CPU_CTRL);
+	gic_cpu_if_up();
 }
 
 static int gic_notifier(struct notifier_block *self, unsigned long cmd,	void *v)

include/linux/irqchip/arm-gic.h

@@ -25,6 +25,7 @@
 #define GICC_INT_PRI_THRESHOLD		0xf0
 #define GICC_IAR_INT_ID_MASK		0x3ff
 #define GICC_INT_SPURIOUS		1023
+#define GICC_DIS_BYPASS_MASK		0x1e0
 
 #define GIC_DIST_CTRL			0x000
 #define GIC_DIST_CTR			0x004