ARM: OMAP: clockdomain: Fix locking on _clkdm_clk_hwmod_enable / disable

Previously the code only acquired spinlock after increasing / decreasing
the usecount value, which is wrong. This leaves a small window where
a task switch may occur between the check of the usecount and the actual
wakeup / sleep of the domain. Fixed by moving the spinlock locking before
the usecount access. Left the usecount as atomic_t if someone wants an
easy access to the parameter through atomic_read.

Signed-off-by: Tero Kristo <t-kristo@ti.com>
Acked-by: Paul Walmsley <paul@pwsan.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/mach-omap2/clockdomain.c

@@ -925,15 +925,18 @@ static int _clkdm_clk_hwmod_enable(struct clockdomain *clkdm)
 	if (!clkdm || !arch_clkdm || !arch_clkdm->clkdm_clk_enable)
 		return -EINVAL;
 
+	spin_lock_irqsave(&clkdm->lock, flags);
+
 	/*
 	 * For arch's with no autodeps, clkcm_clk_enable
 	 * should be called for every clock instance or hwmod that is
 	 * enabled, so the clkdm can be force woken up.
 	 */
-	if ((atomic_inc_return(&clkdm->usecount) > 1) && autodeps)
+	if ((atomic_inc_return(&clkdm->usecount) > 1) && autodeps) {
+		spin_unlock_irqrestore(&clkdm->lock, flags);
 		return 0;
+	}
 
-	spin_lock_irqsave(&clkdm->lock, flags);
 	arch_clkdm->clkdm_clk_enable(clkdm);
 	pwrdm_state_switch(clkdm->pwrdm.ptr);
 	spin_unlock_irqrestore(&clkdm->lock, flags);
@@ -950,15 +953,19 @@ static int _clkdm_clk_hwmod_disable(struct clockdomain *clkdm)
 	if (!clkdm || !arch_clkdm || !arch_clkdm->clkdm_clk_disable)
 		return -EINVAL;
 
+	spin_lock_irqsave(&clkdm->lock, flags);
+
 	if (atomic_read(&clkdm->usecount) == 0) {
+		spin_unlock_irqrestore(&clkdm->lock, flags);
 		WARN_ON(1); /* underflow */
 		return -ERANGE;
 	}
 
-	if (atomic_dec_return(&clkdm->usecount) > 0)
+	if (atomic_dec_return(&clkdm->usecount) > 0) {
+		spin_unlock_irqrestore(&clkdm->lock, flags);
 		return 0;
+	}
 
-	spin_lock_irqsave(&clkdm->lock, flags);
 	arch_clkdm->clkdm_clk_disable(clkdm);
 	pwrdm_state_switch(clkdm->pwrdm.ptr);
 	spin_unlock_irqrestore(&clkdm->lock, flags);