[PATCH V4] gic: preserve gic V2 bypass bits in cpu ctrl register

[Feng Kan <fkan@apm.com>]

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 bootload regarding
v2 bypass group bits. In the X-Gene platform (as well others), the
bypass functionality is not generally used and bypass bits should not
be changed by the kernel gic code as it could lead to incorrect behavior.
Tested on X-Gene mustang board.

Signed-off-by: Vinayak Kale <vkale@apm.com>
Acked-by: Anup Patel <apatel@apm.com>
Signed-off-by: Feng Kan <fkan@apm.com>
---
 V4: Change to use bypass mask, change to use more suitable variable name.
 V3: Fix code not touch other bits other than bypass bits.

 drivers/irqchip/irq-gic.c |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index 4300b66..50a7bb2 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -97,6 +97,8 @@ struct irq_chip gic_arch_extn = {
 #define MAX_GIC_NR	1
 #endif
 
+#define GIC_BYPASS_MASK		0x1e0
+
 static struct gic_chip_data gic_data[MAX_GIC_NR] __read_mostly;
 
 #ifdef CONFIG_GIC_NON_BANKED
@@ -418,6 +420,7 @@ static void gic_cpu_init(struct gic_chip_data *gic)
 	void __iomem *dist_base = gic_data_dist_base(gic);
 	void __iomem *base = gic_data_cpu_base(gic);
 	unsigned int cpu_mask, cpu = smp_processor_id();
+	unsigned int bypass;
 	int i;
 
 	/*
@@ -449,13 +452,20 @@ static void gic_cpu_init(struct gic_chip_data *gic)
 		writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4 / 4);
 
 	writel_relaxed(0xf0, base + GIC_CPU_PRIMASK);
-	writel_relaxed(1, base + GIC_CPU_CTRL);
+
+	bypass = readl(base + GIC_CPU_CTRL);
+	bypass &= GIC_BYPASS_MASK;
+	writel_relaxed(bypass | 0x1, base + GIC_CPU_CTRL);
 }
 
 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);
+	unsigned int bypass;
+
+	bypass = readl(cpu_base + GIC_CPU_CTRL);
+	bypass &= GIC_BYPASS_MASK;
+	writel_relaxed(bypass, cpu_base + GIC_CPU_CTRL);
 }
 
 #ifdef CONFIG_CPU_PM
@@ -566,6 +576,7 @@ static void gic_cpu_restore(unsigned int gic_nr)
 {
 	int i;
 	u32 *ptr;
+	unsigned int bypass;
 	void __iomem *dist_base;
 	void __iomem *cpu_base;
 
@@ -590,7 +601,10 @@ static void gic_cpu_restore(unsigned int gic_nr)
 		writel_relaxed(0xa0a0a0a0, dist_base + GIC_DIST_PRI + i * 4);
 
 	writel_relaxed(0xf0, cpu_base + GIC_CPU_PRIMASK);
-	writel_relaxed(1, cpu_base + GIC_CPU_CTRL);
+
+	bypass = readl(cpu_base + GIC_CPU_CTRL);
+	bypass &= GIC_BYPASS_MASK;
+	writel_relaxed(bypass | 0x1, cpu_base + GIC_CPU_CTRL);
 }
 
 static int gic_notifier(struct notifier_block *self, unsigned long cmd,	void *v)
-- 
1.7.6.1