1 files changed, 24 insertions, 4 deletions

diff --git a/drivers/rtc/rtc-at91sam9.c b/drivers/rtc/rtc-at91sam9.c
index be9c28b9d057..abac38abd38e 100644
--- a/drivers/rtc/rtc-at91sam9.c
+++ b/drivers/rtc/rtc-at91sam9.c
@@ -23,6 +23,7 @@
 #include <linux/io.h>
 #include <linux/mfd/syscon.h>
 #include <linux/regmap.h>
+#include <linux/clk.h>
 
 /*
  * This driver uses two configurable hardware resources that live in the
@@ -61,8 +62,6 @@
 #define AT91_RTT_ALMS           (1 << 0)                /* Real-time Alarm Status */
 #define AT91_RTT_RTTINC         (1 << 1)                /* Real-time Timer Increment */
 
-#define AT91_SLOW_CLOCK         32768
-
 /*
  * We store ALARM_DISABLED in ALMV to record that no alarm is set.
  * It's also the reset value for that field.
@@ -77,6 +76,7 @@ struct sam9_rtc {
         struct regmap           *gpbr;
         unsigned int            gpbr_offset;
         int                     irq;
+        struct clk              *sclk;
 };
 
 #define rtt_readl(rtc, field) \
@@ -328,6 +328,7 @@ static int at91_rtc_probe(struct platform_device *pdev)
         struct sam9_rtc *rtc;
         int             ret, irq;
         u32             mr;
+        unsigned int    sclk_rate;
 
         irq = platform_get_irq(pdev, 0);
         if (irq < 0) {
@@ -385,11 +386,27 @@ static int at91_rtc_probe(struct platform_device *pdev)
                 return -ENOMEM;
         }
 
+        rtc->sclk = devm_clk_get(&pdev->dev, NULL);
+        if (IS_ERR(rtc->sclk))
+                return PTR_ERR(rtc->sclk);
+
+        sclk_rate = clk_get_rate(rtc->sclk);
+        if (!sclk_rate || sclk_rate > AT91_RTT_RTPRES) {
+                dev_err(&pdev->dev, "Invalid slow clock rate\n");
+                return -EINVAL;
+        }
+
+        ret = clk_prepare_enable(rtc->sclk);
+        if (ret) {
+                dev_err(&pdev->dev, "Could not enable slow clock\n");
+                return ret;
+        }
+
         mr = rtt_readl(rtc, MR);
 
         /* unless RTT is counting at 1 Hz, re-initialize it */
-        if ((mr & AT91_RTT_RTPRES) != AT91_SLOW_CLOCK) {
-                mr = AT91_RTT_RTTRST | (AT91_SLOW_CLOCK & AT91_RTT_RTPRES);
+        if ((mr & AT91_RTT_RTPRES) != sclk_rate) {
+                mr = AT91_RTT_RTTRST | (sclk_rate & AT91_RTT_RTPRES);
                 gpbr_writel(rtc, 0);
         }
 
@@ -434,6 +451,9 @@ static int at91_rtc_remove(struct platform_device *pdev)
         /* disable all interrupts */
         rtt_writel(rtc, MR, mr & ~(AT91_RTT_ALMIEN | AT91_RTT_RTTINCIEN));
 
+        if (!IS_ERR(rtc->sclk))
+                clk_disable_unprepare(rtc->sclk);
+
         return 0;
 }