2 files changed, 65 insertions, 6 deletions

diff --git a/Documentation/devicetree/bindings/rtc/stmp3xxx-rtc.txt b/Documentation/devicetree/bindings/rtc/stmp3xxx-rtc.txt
index b800070fe6e9..fa6a94226669 100644
--- a/Documentation/devicetree/bindings/rtc/stmp3xxx-rtc.txt
+++ b/Documentation/devicetree/bindings/rtc/stmp3xxx-rtc.txt
@@ -7,6 +7,11 @@ Required properties:
   region.
 - interrupts: rtc alarm interrupt
 
+Optional properties:
+- stmp,crystal-freq: override crystal frequency as determined from fuse bits.
+  Only <32000> and <32768> are possible for the hardware.  Use <0> for
+  "no crystal".
+
 Example:
 
 rtc@80056000 {
diff --git a/drivers/rtc/rtc-stmp3xxx.c b/drivers/rtc/rtc-stmp3xxx.c
index 2939cdcb2688..eb09eddf39b8 100644
--- a/drivers/rtc/rtc-stmp3xxx.c
+++ b/drivers/rtc/rtc-stmp3xxx.c
@@ -42,6 +42,8 @@
 #define STMP3XXX_RTC_STAT                       0x10
 #define STMP3XXX_RTC_STAT_STALE_SHIFT           16
 #define STMP3XXX_RTC_STAT_RTC_PRESENT           0x80000000
+#define STMP3XXX_RTC_STAT_XTAL32000_PRESENT     0x10000000
+#define STMP3XXX_RTC_STAT_XTAL32768_PRESENT     0x08000000
 
 #define STMP3XXX_RTC_SECONDS                    0x30
 
@@ -52,9 +54,13 @@
 #define STMP3XXX_RTC_PERSISTENT0                0x60
 #define STMP3XXX_RTC_PERSISTENT0_SET            0x64
 #define STMP3XXX_RTC_PERSISTENT0_CLR            0x68
-#define STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN  0x00000002
-#define STMP3XXX_RTC_PERSISTENT0_ALARM_EN       0x00000004
-#define STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE     0x00000080
+#define STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE            (1 << 0)
+#define STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN          (1 << 1)
+#define STMP3XXX_RTC_PERSISTENT0_ALARM_EN               (1 << 2)
+#define STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP        (1 << 4)
+#define STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP        (1 << 5)
+#define STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ            (1 << 6)
+#define STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE             (1 << 7)
 
 #define STMP3XXX_RTC_PERSISTENT1                0x70
 /* missing bitmask in headers */
@@ -248,6 +254,9 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
 {
         struct stmp3xxx_rtc_data *rtc_data;
         struct resource *r;
+        u32 rtc_stat;
+        u32 pers0_set, pers0_clr;
+        u32 crystalfreq = 0;
         int err;
 
         rtc_data = devm_kzalloc(&pdev->dev, sizeof(*rtc_data), GFP_KERNEL);
@@ -268,8 +277,8 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
 
         rtc_data->irq_alarm = platform_get_irq(pdev, 0);
 
-        if (!(readl(STMP3XXX_RTC_STAT + rtc_data->io) &
-                        STMP3XXX_RTC_STAT_RTC_PRESENT)) {
+        rtc_stat = readl(rtc_data->io + STMP3XXX_RTC_STAT);
+        if (!(rtc_stat & STMP3XXX_RTC_STAT_RTC_PRESENT)) {
                 dev_err(&pdev->dev, "no device onboard\n");
                 return -ENODEV;
         }
@@ -282,9 +291,54 @@ static int stmp3xxx_rtc_probe(struct platform_device *pdev)
                 return err;
         }
 
+        /*
+         * Obviously the rtc needs a clock input to be able to run.
+         * This clock can be provided by an external 32k crystal. If that one is
+         * missing XTAL must not be disabled in suspend which consumes a
+         * lot of power. Normally the presence and exact frequency (supported
+         * are 32000 Hz and 32768 Hz) is detectable from fuses, but as reality
+         * proves these fuses are not blown correctly on all machines, so the
+         * frequency can be overridden in the device tree.
+         */
+        if (rtc_stat & STMP3XXX_RTC_STAT_XTAL32000_PRESENT)
+                crystalfreq = 32000;
+        else if (rtc_stat & STMP3XXX_RTC_STAT_XTAL32768_PRESENT)
+                crystalfreq = 32768;
+
+        of_property_read_u32(pdev->dev.of_node, "stmp,crystal-freq",
+                             &crystalfreq);
+
+        switch (crystalfreq) {
+        case 32000:
+                /* keep 32kHz crystal running in low-power mode */
+                pers0_set = STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ |
+                        STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
+                        STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE;
+                pers0_clr = STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP;
+                break;
+        case 32768:
+                /* keep 32.768kHz crystal running in low-power mode */
+                pers0_set = STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
+                        STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE;
+                pers0_clr = STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP |
+                        STMP3XXX_RTC_PERSISTENT0_XTAL32_FREQ;
+                break;
+        default:
+                dev_warn(&pdev->dev,
+                         "invalid crystal-freq specified in device-tree. Assuming no crystal\n");
+                /* fall-through */
+        case 0:
+                /* keep XTAL on in low-power mode */
+                pers0_set = STMP3XXX_RTC_PERSISTENT0_XTAL24MHZ_PWRUP;
+                pers0_clr = STMP3XXX_RTC_PERSISTENT0_XTAL32KHZ_PWRUP |
+                        STMP3XXX_RTC_PERSISTENT0_CLOCKSOURCE;
+        }
+
+        writel(pers0_set, rtc_data->io + STMP3XXX_RTC_PERSISTENT0_SET);
+
         writel(STMP3XXX_RTC_PERSISTENT0_ALARM_EN |
                         STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE_EN |
-                        STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE,
+                        STMP3XXX_RTC_PERSISTENT0_ALARM_WAKE | pers0_clr,
                         rtc_data->io + STMP3XXX_RTC_PERSISTENT0_CLR);
 
         writel(STMP3XXX_RTC_CTRL_ONEMSEC_IRQ_EN |