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ARM: imx: fix shared gate clock 

Let's say clock A and B are two gate clocks that share the same register
bit in hardware.  Therefore they are registered as shared gate clocks
with imx_clk_gate2_shared().

In a scenario that only clock A is enabled by clk_enable(A) while B is
not used, the shared gate will be unexpectedly disabled in hardware.
It happens because clk_enable(A) increments the share_count from 0 to 1,
while clock B is unused to clock core, and therefore the core function
will just disable B by calling clk->ops->disable() directly.  The
consequence of that call is share_count is decremented to 0 and the gate
is disabled in hardware, even though clock A is still in use.

The patch fixes the issue by initializing the share_count per hardware
state and returns enable state per share_count from .is_enabled() hook,
in case it's a shared gate.

While at it, add a check in clk_gate2_disable() to ensure it's never
called with a zero share_count.

Reported-by: Fabio Estevam <fabio.estevam@freescale.com>
Fixes: f9f28cdf21 ("ARM: imx: add shared gate clock support")
Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: Olof Johansson <olof@lixom.net>
This commit is contained in:
Shawn Guo 2014-07-07 10:53:51 +08:00 committed by Olof Johansson
parent 069c70cb07
commit 63288b721a
1 changed files with 23 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
arch/arm/mach-imx/clk-gate2.c
View File

@ -67,8 +67,12 @@ static void clk_gate2_disable(struct clk_hw *hw)
spin_lock_irqsave(gate->lock, flags);
if (gate->share_count && --(*gate->share_count) > 0)
if (gate->share_count) {
if (WARN_ON(*gate->share_count == 0))
goto out;
else if (--(*gate->share_count) > 0)
goto out;
}
reg = readl(gate->reg);
reg &= ~(3 << gate->bit_idx);
@ -78,19 +82,26 @@ static void clk_gate2_disable(struct clk_hw *hw)
spin_unlock_irqrestore(gate->lock, flags);
}
static int clk_gate2_is_enabled(struct clk_hw *hw)
static int clk_gate2_reg_is_enabled(void __iomem *reg, u8 bit_idx)
{
u32 reg;
struct clk_gate2 *gate = to_clk_gate2(hw);
u32 val = readl(reg);
reg = readl(gate->reg);
if (((reg >> gate->bit_idx) & 1) == 1)
if (((val >> bit_idx) & 1) == 1)
return 1;
return 0;
}
static int clk_gate2_is_enabled(struct clk_hw *hw)
{
struct clk_gate2 *gate = to_clk_gate2(hw);
if (gate->share_count)
return !!(*gate->share_count);
else
return clk_gate2_reg_is_enabled(gate->reg, gate->bit_idx);
}
static struct clk_ops clk_gate2_ops = {
.enable = clk_gate2_enable,
.disable = clk_gate2_disable,
@ -116,6 +127,10 @@ struct clk *clk_register_gate2(struct device *dev, const char *name,
gate->bit_idx = bit_idx;
gate->flags = clk_gate2_flags;
gate->lock = lock;
/* Initialize share_count per hardware state */
if (share_count)
*share_count = clk_gate2_reg_is_enabled(reg, bit_idx) ? 1 : 0;
gate->share_count = share_count;
init.name = name;