4 files changed, 88 insertions, 0 deletions

diff --git a/Documentation/devicetree/bindings/rtc/rtc-cmos.txt b/Documentation/devicetree/bindings/rtc/rtc-cmos.txt
new file mode 100644
index 00000000000..7382989b305
--- /dev/null
+++ b/Documentation/devicetree/bindings/rtc/rtc-cmos.txt
@@ -0,0 +1,28 @@
+ Motorola mc146818 compatible RTC
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Required properties:
+  - compatible : "motorola,mc146818"
+  - reg : should contain registers location and length.
+
+Optional properties:
+  - interrupts : should contain interrupt.
+  - interrupt-parent : interrupt source phandle.
+  - ctrl-reg : Contains the initial value of the control register also
+    called "Register B".
+  - freq-reg : Contains the initial value of the frequency register also
+    called "Regsiter A".
+
+"Register A" and "B" are usually initialized by the firmware (BIOS for
+instance). If this is not done, it can be performed by the driver.
+
+ISA Example:
+
+        rtc@70 {
+                 compatible = "motorola,mc146818";
+                 interrupts = <8 3>;
+                 interrupt-parent = <&ioapic1>;
+                 ctrl-reg = <2>;
+                 freq-reg = <0x26>;
+                 reg = <1 0x70 2>;
+         };
diff --git a/arch/x86/kernel/rtc.c b/arch/x86/kernel/rtc.c
index 6f39cab052d..3f2ad2640d8 100644
--- a/arch/x86/kernel/rtc.c
+++ b/arch/x86/kernel/rtc.c
@@ -6,6 +6,7 @@
 #include <linux/acpi.h>
 #include <linux/bcd.h>
 #include <linux/pnp.h>
+#include <linux/of.h>
 
 #include <asm/vsyscall.h>
 #include <asm/x86_init.h>
@@ -236,6 +237,8 @@ static __init int add_rtc_cmos(void)
                 }
         }
 #endif
+        if (of_have_populated_dt())
+                return 0;
 
         platform_device_register(&rtc_device);
         dev_info(&rtc_device.dev,
diff --git a/drivers/rtc/rtc-cmos.c b/drivers/rtc/rtc-cmos.c
index c7ff8df347e..159b95e4b42 100644
--- a/drivers/rtc/rtc-cmos.c
+++ b/drivers/rtc/rtc-cmos.c
@@ -37,6 +37,8 @@
 #include <linux/mod_devicetable.h>
 #include <linux/log2.h>
 #include <linux/pm.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
 
 /* this is for "generic access to PC-style RTC" using CMOS_READ/CMOS_WRITE */
 #include <asm-generic/rtc.h>
@@ -1123,6 +1125,47 @@ static struct pnp_driver cmos_pnp_driver = {
 
 #endif  /* CONFIG_PNP */
 
+#ifdef CONFIG_OF
+static const struct of_device_id of_cmos_match[] = {
+        {
+                .compatible = "motorola,mc146818",
+        },
+        { },
+};
+MODULE_DEVICE_TABLE(of, of_cmos_match);
+
+static __init void cmos_of_init(struct platform_device *pdev)
+{
+        struct device_node *node = pdev->dev.of_node;
+        struct rtc_time time;
+        int ret;
+        const __be32 *val;
+
+        if (!node)
+                return;
+
+        val = of_get_property(node, "ctrl-reg", NULL);
+        if (val)
+                CMOS_WRITE(be32_to_cpup(val), RTC_CONTROL);
+
+        val = of_get_property(node, "freq-reg", NULL);
+        if (val)
+                CMOS_WRITE(be32_to_cpup(val), RTC_FREQ_SELECT);
+
+        get_rtc_time(&time);
+        ret = rtc_valid_tm(&time);
+        if (ret) {
+                struct rtc_time def_time = {
+                        .tm_year = 1,
+                        .tm_mday = 1,
+                };
+                set_rtc_time(&def_time);
+        }
+}
+#else
+static inline void cmos_of_init(struct platform_device *pdev) {}
+#define of_cmos_match NULL
+#endif
 /*----------------------------------------------------------------*/
 
 /* Platform setup should have set up an RTC device, when PNP is
@@ -1131,6 +1174,7 @@ static struct pnp_driver cmos_pnp_driver = {
 
 static int __init cmos_platform_probe(struct platform_device *pdev)
 {
+        cmos_of_init(pdev);
         cmos_wake_setup(&pdev->dev);
         return cmos_do_probe(&pdev->dev,
                         platform_get_resource(pdev, IORESOURCE_IO, 0),
@@ -1162,6 +1206,7 @@ static struct platform_driver cmos_platform_driver = {
 #ifdef CONFIG_PM
                 .pm             = &cmos_pm_ops,
 #endif
+                .of_match_table = of_cmos_match,
         }
 };
 
diff --git a/include/linux/of.h b/include/linux/of.h
index d9dd664a6a9..266db1d0baa 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -70,6 +70,11 @@ extern struct device_node *allnodes;
 extern struct device_node *of_chosen;
 extern rwlock_t devtree_lock;
 
+static inline bool of_have_populated_dt(void)
+{
+        return allnodes != NULL;
+}
+
 static inline bool of_node_is_root(const struct device_node *node)
 {
         return node && (node->parent == NULL);
@@ -222,5 +227,12 @@ extern void of_attach_node(struct device_node *);
 extern void of_detach_node(struct device_node *);
 #endif
 
+#else
+
+static inline bool of_have_populated_dt(void)
+{
+        return false;
+}
+
 #endif /* CONFIG_OF */
 #endif /* _LINUX_OF_H */