ENGR00221975 Fix race condition in clock code.

Need to ensure that check for usecount in clk_set_parent
occurs within the protection of the clock mutex. Else
there is a chance that the usecount can be decremented
(and the clock disabled) after the check.
Also add back the code to maintain the correct usecount
for pll2_pfd_400.

Signed-off-by: Ranjani Vaidyanathan <ra5478@freescale.com>

3 files changed, 20 insertions, 6 deletions

diff --git a/arch/arm/mach-mx6/clock.c b/arch/arm/mach-mx6/clock.c
index 81b63a55c529..c2bf20177909 100644
--- a/arch/arm/mach-mx6/clock.c
+++ b/arch/arm/mach-mx6/clock.c
@@ -1262,6 +1262,7 @@ static int _clk_arm_set_rate(struct clk *clk, unsigned long rate)
 		  */
 		if (pll1_sw_clk.parent != &pll2_pfd_400M) {
 			pll2_pfd_400M.enable(&pll2_pfd_400M);
+			pll2_pfd_400M.usecount++;
 			arm_needs_pll2_400 = true;
 			pll1_sw_clk.set_parent(&pll1_sw_clk, &pll2_pfd_400M);
 			pll1_sw_clk.parent = &pll2_pfd_400M;
@@ -1287,6 +1288,8 @@ static int _clk_arm_set_rate(struct clk *clk, unsigned long rate)
 		/* Make sure pll1_sw_clk is from pll1_sys_main_clk */
 		pll1_sw_clk.set_parent(&pll1_sw_clk, &pll1_sys_main_clk);
 		pll1_sw_clk.parent = &pll1_sys_main_clk;
+		if (arm_needs_pll2_400)
+			pll2_pfd_400M.usecount--;
 		arm_needs_pll2_400 = false;
 		if (pll2_pfd_400M.usecount == 0)
 			pll2_pfd_400M.disable(&pll2_pfd_400M);
diff --git a/arch/arm/mach-mx6/clock_mx6sl.c b/arch/arm/mach-mx6/clock_mx6sl.c
index 7a66d10c3aab..43b2bd1baac2 100755
--- a/arch/arm/mach-mx6/clock_mx6sl.c
+++ b/arch/arm/mach-mx6/clock_mx6sl.c
@@ -1169,6 +1169,7 @@ static int _clk_arm_set_rate(struct clk *clk, unsigned long rate)
 		if (pll1_sw_clk.parent != &pll2_pfd2_400M) {
 			pll2_pfd2_400M.enable(&pll2_pfd2_400M);
 			arm_needs_pll2_400 = true;
+			pll2_pfd2_400M.usecount++;
 			pll1_sw_clk.set_parent(&pll1_sw_clk, &pll2_pfd2_400M);
 			pll1_sw_clk.parent = &pll2_pfd2_400M;
 		}
@@ -1191,6 +1192,8 @@ static int _clk_arm_set_rate(struct clk *clk, unsigned long rate)
 		pll1_sw_clk.set_parent(&pll1_sw_clk, &pll1_sys_main_clk);
 		pll1_sw_clk.parent = &pll1_sys_main_clk;
 
+		if (arm_needs_pll2_400)
+			pll2_pfd2_400M.usecount--;
 		arm_needs_pll2_400 = false;
 		if (pll2_pfd2_400M.usecount == 0)
 			pll2_pfd2_400M.disable(&pll2_pfd2_400M);
diff --git a/arch/arm/plat-mxc/clock.c b/arch/arm/plat-mxc/clock.c
index ee4ea63d9fdc..93347eb14c69 100755
--- a/arch/arm/plat-mxc/clock.c
+++ b/arch/arm/plat-mxc/clock.c
@@ -225,10 +225,18 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 	    IS_ERR(parent) || clk->set_parent == NULL)
 		return ret;
 
-	if (clk->usecount)
-		clk_enable(parent);
-
 	mutex_lock(&clocks_mutex);
+
+	if (clk->usecount) {
+		if (in_interrupt()) {
+			printk(KERN_ERR " clk_enable cannot be called in an interrupt context\n");
+			dump_stack();
+			mutex_unlock(&clocks_mutex);
+			BUG();
+		}
+		__clk_enable(parent);
+	}
+
 	ret = clk->set_parent(clk, parent);
 	if (ret == 0) {
 		old = clk->parent;
@@ -236,10 +244,10 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 	} else {
 		old = parent;
 	}
-	mutex_unlock(&clocks_mutex);
-
 	if (clk->usecount)
-		clk_disable(old);
+		__clk_disable(old);
+
+	mutex_unlock(&clocks_mutex);
 
 	return ret;
 }