rtc: rtc-mv: Add support for clk to avoid lockups

The Marvell RTC on Kirkwood makes use of the runit clock. Ensure the
driver clk_prepare_enable() this clock, otherwise there is a danger
the SoC will lockup when accessing RTC registers with the clock
disabled.

Reported-by: Simon Baatz <gmbnomis@gmail.com>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Tested-by: Simon Baatz <gmbnomis@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>

2 files changed, 25 insertions, 4 deletions

diff --git a/arch/arm/boot/dts/kirkwood.dtsi b/arch/arm/boot/dts/kirkwood.dtsi
index cf8e8926a034..fada7e6d24d8 100644
--- a/arch/arm/boot/dts/kirkwood.dtsi
+++ b/arch/arm/boot/dts/kirkwood.dtsi
@@ -75,6 +75,7 @@
                         compatible = "marvell,kirkwood-rtc", "marvell,orion-rtc";
                         reg = <0x10300 0x20>;
                         interrupts = <53>;
+                        clocks = <&gate_clk 7>;
                 };
 
                 spi@10600 {
diff --git a/drivers/rtc/rtc-mv.c b/drivers/rtc/rtc-mv.c
index 57233c885998..8f87fec27ce7 100644
--- a/drivers/rtc/rtc-mv.c
+++ b/drivers/rtc/rtc-mv.c
@@ -14,6 +14,7 @@
 #include <linux/platform_device.h>
 #include <linux/of.h>
 #include <linux/delay.h>
+#include <linux/clk.h>
 #include <linux/gfp.h>
 #include <linux/module.h>
 
@@ -41,6 +42,7 @@ struct rtc_plat_data {
         struct rtc_device *rtc;
         void __iomem *ioaddr;
         int             irq;
+        struct clk      *clk;
 };
 
 static int mv_rtc_set_time(struct device *dev, struct rtc_time *tm)
@@ -221,6 +223,7 @@ static int mv_rtc_probe(struct platform_device *pdev)
         struct rtc_plat_data *pdata;
         resource_size_t size;
         u32 rtc_time;
+        int ret = 0;
 
         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
         if (!res)
@@ -239,11 +242,17 @@ static int mv_rtc_probe(struct platform_device *pdev)
         if (!pdata->ioaddr)
                 return -ENOMEM;
 
+        pdata->clk = devm_clk_get(&pdev->dev, NULL);
+        /* Not all SoCs require a clock.*/
+        if (!IS_ERR(pdata->clk))
+                clk_prepare_enable(pdata->clk);
+
         /* make sure the 24 hours mode is enabled */
         rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
         if (rtc_time & RTC_HOURS_12H_MODE) {
                 dev_err(&pdev->dev, "24 Hours mode not supported.\n");
-                return -EINVAL;
+                ret = -EINVAL;
+                goto out;
         }
 
         /* make sure it is actually functional */
@@ -252,7 +261,8 @@ static int mv_rtc_probe(struct platform_device *pdev)
                 rtc_time = readl(pdata->ioaddr + RTC_TIME_REG_OFFS);
                 if (rtc_time == 0x01000000) {
                         dev_err(&pdev->dev, "internal RTC not ticking\n");
-                        return -ENODEV;
+                        ret = -ENODEV;
+                        goto out;
                 }
         }
 
@@ -268,8 +278,10 @@ static int mv_rtc_probe(struct platform_device *pdev)
         } else
                 pdata->rtc = rtc_device_register(pdev->name, &pdev->dev,
                                                  &mv_rtc_ops, THIS_MODULE);
-        if (IS_ERR(pdata->rtc))
-                return PTR_ERR(pdata->rtc);
+        if (IS_ERR(pdata->rtc)) {
+                ret = PTR_ERR(pdata->rtc);
+                goto out;
+        }
 
         if (pdata->irq >= 0) {
                 writel(0, pdata->ioaddr + RTC_ALARM_INTERRUPT_MASK_REG_OFFS);
@@ -282,6 +294,11 @@ static int mv_rtc_probe(struct platform_device *pdev)
         }
 
         return 0;
+out:
+        if (!IS_ERR(pdata->clk))
+                clk_disable_unprepare(pdata->clk);
+
+        return ret;
 }
 
 static int __exit mv_rtc_remove(struct platform_device *pdev)
@@ -292,6 +309,9 @@ static int __exit mv_rtc_remove(struct platform_device *pdev)
                 device_init_wakeup(&pdev->dev, 0);
 
         rtc_device_unregister(pdata->rtc);
+        if (!IS_ERR(pdata->clk))
+                clk_disable_unprepare(pdata->clk);
+
         return 0;
 }