clocksource: dw_apb_timer_of: enable the use the clocksource as sched clock

Currently the dw_apb_timer always expects a separate special timer to be
availbable for the sched_clock. Some devices using dw_apb_timers do not
have this sptimer but can use the clocksource as sched_clock instead.

Therefore enable the driver to distiguish between devices with and without
sptimer based on the devicetree data and select the correct timer as
sched_clock.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Jamie Iles <jamie@jamieiles.com>

1 files changed, 17 insertions, 9 deletions

diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
index ab09ed3742ee..d6c0fda76a7e 100644
--- a/drivers/clocksource/dw_apb_timer_of.c
+++ b/drivers/clocksource/dw_apb_timer_of.c
@@ -57,6 +57,9 @@ static void add_clockevent(struct device_node *event_timer)
         dw_apb_clockevent_register(ced);
 }
 
+static void __iomem *sched_io_base;
+static u32 sched_rate;
+
 static void add_clocksource(struct device_node *source_timer)
 {
         void __iomem *iobase;
@@ -71,9 +74,15 @@ static void add_clocksource(struct device_node *source_timer)
 
         dw_apb_clocksource_start(cs);
         dw_apb_clocksource_register(cs);
-}
 
-static void __iomem *sched_io_base;
+        /*
+         * Fallback to use the clocksource as sched_clock if no separate
+         * timer is found. sched_io_base then points to the current_value
+         * register of the clocksource timer.
+         */
+        sched_io_base = iobase + 0x04;
+        sched_rate = rate;
+}
 
 static u32 read_sched_clock(void)
 {
@@ -89,16 +98,15 @@ static const struct of_device_id sptimer_ids[] __initconst = {
 static void init_sched_clock(void)
 {
         struct device_node *sched_timer;
-        u32 rate;
 
         sched_timer = of_find_matching_node(NULL, sptimer_ids);
-        if (!sched_timer)
-                panic("No RTC for sched clock to use");
-
-        timer_get_base_and_rate(sched_timer, &sched_io_base, &rate);
-        of_node_put(sched_timer);
+        if (sched_timer) {
+                timer_get_base_and_rate(sched_timer, &sched_io_base,
+                                        &sched_rate);
+                of_node_put(sched_timer);
+        }
 
-        setup_sched_clock(read_sched_clock, 32, rate);
+        setup_sched_clock(read_sched_clock, 32, sched_rate);
 }
 
 static const struct of_device_id osctimer_ids[] __initconst = {