[RFC PATCH 12/17] ARM: kernel: add SCU reset hook

[Lorenzo Pieralisi]

When a CLUSTER is powered down the SCU must be reinitialized on
warm-boot.
This patch adds a hook to reset the SCU, which implies invalidating
TAG RAMs and renabling it.

The scu virtual address is saved in a static variable when the SCU
is first enabled at boot; this allows common idle code to be
generic and avoid relying on platform code to get the address at
run-time.
On warm-boot the SCU TAG RAM is invalidated and the SCU enabled if
it is not already enabled.

The reset can be skipped altogether thanks to save/restore
framework flags.

Flushing D$ cache is cumbersome since the system just comes out of
reset, which invalidates caches in the process if needed (A9), that
is why the scu_enable function is not reused as it is to reset the SCU.

If the init function is extended, there might not be a need for
a SCU specific hook, since the init function can be reused to
reinitialize the SCU at boot provided it is removed from the init
section and kept in memory.

Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi at arm.com>
---
 arch/arm/include/asm/smp_scu.h |    3 ++-
 arch/arm/kernel/smp_scu.c      |   33 ++++++++++++++++++++++++++++++---
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/arch/arm/include/asm/smp_scu.h b/arch/arm/include/asm/smp_scu.h
index 4eb6d00..cfaa68e 100644
--- a/arch/arm/include/asm/smp_scu.h
+++ b/arch/arm/include/asm/smp_scu.h
@@ -8,7 +8,8 @@
 #ifndef __ASSEMBLER__
 unsigned int scu_get_core_count(void __iomem *);
 void scu_enable(void __iomem *);
-int scu_power_mode(void __iomem *, unsigned int);
+int scu_power_mode(unsigned int);
+void scu_reset(void);
 #endif
 
 #endif
diff --git a/arch/arm/kernel/smp_scu.c b/arch/arm/kernel/smp_scu.c
index a1e757c..980ced9 100644
--- a/arch/arm/kernel/smp_scu.c
+++ b/arch/arm/kernel/smp_scu.c
@@ -20,6 +20,7 @@
 #define SCU_INVALIDATE		0x0c
 #define SCU_FPGA_REVISION	0x10
 
+static void __iomem *scu_va;
 /*
  * Get the number of CPU cores from the SCU configuration
  */
@@ -36,6 +37,7 @@ void __init scu_enable(void __iomem *scu_base)
 {
 	u32 scu_ctrl;
 
+	scu_va = scu_base;
 	scu_ctrl = __raw_readl(scu_base + SCU_CTRL);
 	/* already enabled? */
 	if (scu_ctrl & 1)
@@ -59,7 +61,7 @@ void __init scu_enable(void __iomem *scu_base)
  * has the side effect of disabling coherency, caches must have been
  * flushed.  Interrupts must also have been disabled.
  */
-int scu_power_mode(void __iomem *scu_base, unsigned int mode)
+int scu_power_mode(unsigned int mode)
 {
 	unsigned int val;
 	int cpu = smp_processor_id();
@@ -67,9 +69,34 @@ int scu_power_mode(void __iomem *scu_base, unsigned int mode)
 	if (mode > 3 || mode == 1 || cpu > 3)
 		return -EINVAL;
 
-	val = __raw_readb(scu_base + SCU_CPU_STATUS + cpu) & ~0x03;
+	val = __raw_readb(scu_va + SCU_CPU_STATUS + cpu) & ~0x03;
 	val |= mode;
-	__raw_writeb(val, scu_base + SCU_CPU_STATUS + cpu);
+	__raw_writeb(val, scu_va + SCU_CPU_STATUS + cpu);
 
 	return 0;
 }
+
+/*
+ * Reinitialise the SCU after power-down
+ */
+
+void scu_reset(void)
+{
+	u32 scu_ctrl;
+
+	scu_ctrl = __raw_readl(scu_va + SCU_CTRL);
+	/* already enabled? */
+	if (scu_ctrl & 1)
+		return;
+	/*
+	 * SCU TAGS should be invalidated on boot-up
+	 */
+	__raw_writel(0xffff, scu_va + SCU_INVALIDATE);
+	/*
+	 *  Coming out of reset, dcache invalidated
+	 *  no need to go through the whole hog again
+	 *  just enable the SCU and pop out
+	 */
+	scu_ctrl |= 1;
+	__raw_writel(scu_ctrl, scu_va + SCU_CTRL);
+}
-- 
1.7.4.4