linux-kernel - [PATCH 1/1] gic: change access of gicc_ctrl register to read modify write.

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Date:	Sun,  8 Dec 2013 12:22:37 -0800
From:	Feng Kan <fkan@....com>
To:	patches@....com, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Cc:	Feng Kan <fkan@....com>, Vinayak Kale <vkale@....com>
Subject: [PATCH 1/1] gic: change access of gicc_ctrl register to read modify write.

This change is made to preserve the GIC v2 releated bits in the
GIC_CPU_CTRL register (also known as the GICC_CTLR register in spec).
The original code only set the enable/disable group bit in this register.
This code will preserve all other bits configured by the bootload except
the enable/disable bit. The main reason for this change is to allow the
bypass bits specified in the v2 spec to remain untouched by the current
GIC code. In the X-Gene platform, the bypass functionality is not used
and bypass must be disabled at all time.

Signed-off-by: Vinayak Kale <vkale@....com>
Acked-by: Anup Patel <apatel@....com>
Signed-off-by: Feng Kan <fkan@....com>
---
 drivers/irqchip/irq-gic.c |   19 ++++++++++++++++---
 1 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
index d0e9480..6550ac9 100644
--- a/drivers/irqchip/irq-gic.c
+++ b/drivers/irqchip/irq-gic.c
@@ -419,6 +419,7 @@ 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 ctrl_mask;
 	int i;
 
 	/*
@@ -450,13 +451,21 @@ 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);
+
+	ctrl_mask = readl(base + GIC_CPU_CTRL);
+	ctrl_mask |= 0x1;
+	writel_relaxed(ctrl_mask, base + GIC_CPU_CTRL);
 }
 
 void gic_cpu_if_down(void)
 {
+	unsigned int ctrl_mask;
+
 	void __iomem *cpu_base = gic_data_cpu_base(&gic_data[0]);
-	writel_relaxed(0, cpu_base + GIC_CPU_CTRL);
+
+	ctrl_mask = readl(base + GIC_CPU_CTRL);
+	ctrl_mask &= 0xfffffffe;
+	writel_relaxed(ctrl_mask, cpu_base + GIC_CPU_CTRL);
 }
 
 #ifdef CONFIG_CPU_PM
@@ -567,6 +576,7 @@ static void gic_cpu_restore(unsigned int gic_nr)
 {
 	int i;
 	u32 *ptr;
+	unsigned int ctrl_mask;
 	void __iomem *dist_base;
 	void __iomem *cpu_base;
 
@@ -591,7 +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);
+
+	ctrl_mask = readl(base + GIC_CPU_CTRL);
+	ctrl_mask |= 0x1;
+	writel_relaxed(ctrl_mask, cpu_base + GIC_CPU_CTRL);
 }
 
 static int gic_notifier(struct notifier_block *self, unsigned long cmd,	void *v)
-- 
1.7.6.1

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