clocksource: dw_apb_timer_of: add clock-handling

Add the possibility to get the clock-frequency from a timer clock instead
of specifying it as dt property. Additionally also add the possibility
to also define a controlling periphal clock for the timer block.

The clock-frequency property is kept to act as fallback if no clocks
are specified.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Jamie Iles <jamie@jamieiles.com>

2 files changed, 44 insertions, 1 deletions

diff --git a/Documentation/devicetree/bindings/rtc/dw-apb.txt b/Documentation/devicetree/bindings/rtc/dw-apb.txt
index 93e2b0f048e6..eb2327b2bdb3 100644
--- a/Documentation/devicetree/bindings/rtc/dw-apb.txt
+++ b/Documentation/devicetree/bindings/rtc/dw-apb.txt
@@ -5,9 +5,20 @@ Required properties:
 - reg: physical base address of the controller and length of memory mapped
   region.
 - interrupts: IRQ line for the timer.
+- either clocks+clock-names or clock-frequency properties
+
+Optional properties:
+- clocks        : list of clock specifiers, corresponding to entries in
+                  the clock-names property;
+- clock-names   : should contain "timer" and "pclk" entries, matching entries
+                  in the clocks property.
 - clock-frequency: The frequency in HZ of the timer.
 - clock-freq: For backwards compatibility with picoxcell
 
+If using the clock specifiers, the pclk clock is optional, as not all
+systems may use one.
+
+
 Example:
 
                 timer1: timer@ffc09000 {
@@ -23,3 +34,11 @@ Example:
                                 clock-frequency = <200000000>;
                                 reg = <0xffd00000 0x1000>;
                         };
+
+                timer3: timer@ffe00000 {
+                                compatible = "snps,dw-apb-timer-osc";
+                                interrupts = <0 170 4>;
+                                reg = <0xffe00000 0x1000>;
+                                clocks = <&timer_clk>, <&timer_pclk>;
+                                clock-names = "timer", "pclk";
+                        };
diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
index d6c0fda76a7e..1964f8716966 100644
--- a/drivers/clocksource/dw_apb_timer_of.c
+++ b/drivers/clocksource/dw_apb_timer_of.c
@@ -20,6 +20,7 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
+#include <linux/clk.h>
 
 #include <asm/mach/time.h>
 #include <asm/sched_clock.h>
@@ -27,14 +28,37 @@
 static void timer_get_base_and_rate(struct device_node *np,
                                     void __iomem **base, u32 *rate)
 {
+        struct clk *timer_clk;
+        struct clk *pclk;
+
         *base = of_iomap(np, 0);
 
         if (!*base)
                 panic("Unable to map regs for %s", np->name);
 
+        /*
+         * Not all implementations use a periphal clock, so don't panic
+         * if it's not present
+         */
+        pclk = of_clk_get_by_name(np, "pclk");
+        if (!IS_ERR(pclk))
+                if (clk_prepare_enable(pclk))
+                        pr_warn("pclk for %s is present, but could not be activated\n",
+                                np->name);
+
+        timer_clk = of_clk_get_by_name(np, "timer");
+        if (IS_ERR(timer_clk))
+                goto try_clock_freq;
+
+        if (!clk_prepare_enable(timer_clk)) {
+                *rate = clk_get_rate(timer_clk);
+                return;
+        }
+
+try_clock_freq:
         if (of_property_read_u32(np, "clock-freq", rate) &&
                 of_property_read_u32(np, "clock-frequency", rate))
-                panic("No clock-frequency property for %s", np->name);
+                panic("No clock nor clock-frequency property for %s", np->name);
 }
 
 static void add_clockevent(struct device_node *event_timer)