ARM: imx: add shared gate clock support

It's quite common on i.MX that one gate bit controls the gating of
multiple clocks, i.e. this is a shared gate.  The patch adds the
function imx_clk_gate2_shared() for such case.  The clocks controlled
by the same gate bits should call this function with a pointer to a
single share count variable, so that the gate bits will only be
operated on the first enabling and the last disabling of these shared
gate clocks.

Thanks to Gerhard Sittig <gsi@denx.de> for this idea.

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>

2 files changed, 23 insertions, 3 deletions

diff --git a/arch/arm/mach-imx/clk-gate2.c b/arch/arm/mach-imx/clk-gate2.c
index 0803df9d9c7e..4ba587da89d2 100644
--- a/arch/arm/mach-imx/clk-gate2.c
+++ b/arch/arm/mach-imx/clk-gate2.c
@@ -33,6 +33,7 @@ struct clk_gate2 {
         u8              bit_idx;
         u8              flags;
         spinlock_t      *lock;
+        unsigned int    *share_count;
 };
 
 #define to_clk_gate2(_hw) container_of(_hw, struct clk_gate2, hw)
@@ -45,10 +46,14 @@ static int clk_gate2_enable(struct clk_hw *hw)
 
         spin_lock_irqsave(gate->lock, flags);
 
+        if (gate->share_count && (*gate->share_count)++ > 0)
+                goto out;
+
         reg = readl(gate->reg);
         reg |= 3 << gate->bit_idx;
         writel(reg, gate->reg);
 
+out:
         spin_unlock_irqrestore(gate->lock, flags);
 
         return 0;
@@ -62,10 +67,14 @@ static void clk_gate2_disable(struct clk_hw *hw)
 
         spin_lock_irqsave(gate->lock, flags);
 
+        if (gate->share_count && --(*gate->share_count) > 0)
+                goto out;
+
         reg = readl(gate->reg);
         reg &= ~(3 << gate->bit_idx);
         writel(reg, gate->reg);
 
+out:
         spin_unlock_irqrestore(gate->lock, flags);
 }
 
@@ -91,7 +100,8 @@ static struct clk_ops clk_gate2_ops = {
 struct clk *clk_register_gate2(struct device *dev, const char *name,
                 const char *parent_name, unsigned long flags,
                 void __iomem *reg, u8 bit_idx,
-                u8 clk_gate2_flags, spinlock_t *lock)
+                u8 clk_gate2_flags, spinlock_t *lock,
+                unsigned int *share_count)
 {
         struct clk_gate2 *gate;
         struct clk *clk;
@@ -106,6 +116,7 @@ struct clk *clk_register_gate2(struct device *dev, const char *name,
         gate->bit_idx = bit_idx;
         gate->flags = clk_gate2_flags;
         gate->lock = lock;
+        gate->share_count = share_count;
 
         init.name = name;
         init.ops = &clk_gate2_ops;
diff --git a/arch/arm/mach-imx/clk.h b/arch/arm/mach-imx/clk.h
index 048c5ad8a80b..e29f6ebe9f39 100644
--- a/arch/arm/mach-imx/clk.h
+++ b/arch/arm/mach-imx/clk.h
@@ -28,7 +28,8 @@ struct clk *imx_clk_pllv3(enum imx_pllv3_type type, const char *name,
 struct clk *clk_register_gate2(struct device *dev, const char *name,
                 const char *parent_name, unsigned long flags,
                 void __iomem *reg, u8 bit_idx,
-                u8 clk_gate_flags, spinlock_t *lock);
+                u8 clk_gate_flags, spinlock_t *lock,
+                unsigned int *share_count);
 
 struct clk * imx_obtain_fixed_clock(
                         const char *name, unsigned long rate);
@@ -37,7 +38,15 @@ static inline struct clk *imx_clk_gate2(const char *name, const char *parent,
                 void __iomem *reg, u8 shift)
 {
         return clk_register_gate2(NULL, name, parent, CLK_SET_RATE_PARENT, reg,
-                        shift, 0, &imx_ccm_lock);
+                        shift, 0, &imx_ccm_lock, NULL);
+}
+
+static inline struct clk *imx_clk_gate2_shared(const char *name,
+                const char *parent, void __iomem *reg, u8 shift,
+                unsigned int *share_count)
+{
+        return clk_register_gate2(NULL, name, parent, CLK_SET_RATE_PARENT, reg,
+                        shift, 0, &imx_ccm_lock, share_count);
 }
 
 struct clk *imx_clk_pfd(const char *name, const char *parent_name,