MIPS: Lantiq: Add locking for PMU register and check status afterwards

The PMU register are accessed in a non atomic way and they could be
accessed by different threads simultaneously, which could cause
problems this patch adds locking around the PMU registers. In
addition we now also wait till the PMU is actually deactivated.

[ralf@linux-mips.org: Fix spelling mistake in commit message as noticed
by Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>.]
Signed-off-by: Hauke Mehrtens <hauke.mehrtens@lantiq.com>
Acked-by: John Crispin <blogic@openwrt.org>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/11381/
Patchwork: https://patchwork.linux-mips.org/patch/11396/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/lantiq/xway/sysctrl.c

@@ -4,6 +4,7 @@
  *  by the Free Software Foundation.
  *
  *  Copyright (C) 2011-2012 John Crispin <blogic@openwrt.org>
+ *  Copyright (C) 2013-2015 Lantiq Beteiligungs-GmbH & Co.KG
  */
 
 #include <linux/ioport.h>
@@ -85,15 +86,19 @@ void __iomem *ltq_ebu_membase;
 static u32 ifccr = CGU_IFCCR;
 static u32 pcicr = CGU_PCICR;
 
+static DEFINE_SPINLOCK(g_pmu_lock);
+
 /* legacy function kept alive to ease clkdev transition */
 void ltq_pmu_enable(unsigned int module)
 {
-	int err = 1000000;
+	int retry = 1000000;
 
+	spin_lock(&g_pmu_lock);
 	pmu_w32(pmu_r32(PMU_PWDCR) & ~module, PMU_PWDCR);
-	do {} while (--err && (pmu_r32(PMU_PWDSR) & module));
+	do {} while (--retry && (pmu_r32(PMU_PWDSR) & module));
+	spin_unlock(&g_pmu_lock);
 
-	if (!err)
+	if (!retry)
 		panic("activating PMU module failed!");
 }
 EXPORT_SYMBOL(ltq_pmu_enable);
@@ -101,7 +106,15 @@ EXPORT_SYMBOL(ltq_pmu_enable);
 /* legacy function kept alive to ease clkdev transition */
 void ltq_pmu_disable(unsigned int module)
 {
+	int retry = 1000000;
+
+	spin_lock(&g_pmu_lock);
 	pmu_w32(pmu_r32(PMU_PWDCR) | module, PMU_PWDCR);
+	do {} while (--retry && (!(pmu_r32(PMU_PWDSR) & module)));
+	spin_unlock(&g_pmu_lock);
+
+	if (!retry)
+		pr_warn("deactivating PMU module failed!");
 }
 EXPORT_SYMBOL(ltq_pmu_disable);
 
@@ -123,9 +136,11 @@ static int pmu_enable(struct clk *clk)
 {
 	int retry = 1000000;
 
+	spin_lock(&g_pmu_lock);
 	pmu_w32(pmu_r32(PWDCR(clk->module)) & ~clk->bits,
 		PWDCR(clk->module));
 	do {} while (--retry && (pmu_r32(PWDSR(clk->module)) & clk->bits));
+	spin_unlock(&g_pmu_lock);
 
 	if (!retry)
 		panic("activating PMU module failed!");
@@ -136,8 +151,15 @@ static int pmu_enable(struct clk *clk)
 /* disable a clock gate */
 static void pmu_disable(struct clk *clk)
 {
-	pmu_w32(pmu_r32(PWDCR(clk->module)) | clk->bits,
-		PWDCR(clk->module));
+	int retry = 1000000;
+
+	spin_lock(&g_pmu_lock);
+	pmu_w32(pmu_r32(PWDCR(clk->module)) | clk->bits, PWDCR(clk->module));
+	do {} while (--retry && (!(pmu_r32(PWDSR(clk->module)) & clk->bits)));
+	spin_unlock(&g_pmu_lock);
+
+	if (!retry)
+		pr_warn("deactivating PMU module failed!");
 }
 
 /* the pci enable helper */