From 63288b721a80fb58c00cd47e61a90bc8b33ba588 Mon Sep 17 00:00:00 2001 From: Shawn Guo Date: Mon, 7 Jul 2014 10:53:51 +0800 Subject: [PATCH] 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 Fixes: f9f28cdf2167 ("ARM: imx: add shared gate clock support") Signed-off-by: Shawn Guo Tested-by: Fabio Estevam Signed-off-by: Olof Johansson --- arch/arm/mach-imx/clk-gate2.c | 31 +++++++++++++++++++++++-------- 1 file changed, 23 insertions(+), 8 deletions(-) diff --git a/arch/arm/mach-imx/clk-gate2.c b/arch/arm/mach-imx/clk-gate2.c index 4ba587da89d2..84acdfd1d715 100644 --- a/arch/arm/mach-imx/clk-gate2.c +++ b/arch/arm/mach-imx/clk-gate2.c @@ -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) - goto out; + 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;