clocksource/drivers/dw_apb: Add reset control

Add code to retrieve the reset property from the dw-apb timers and if
the property is available, the safe operation is to assert the timer
into reset, and followed by a deassert of the timer reset (brings the
timer out of reset).

This patch is needed for systems where the bootloader has left the timer
not used in reset.

 - Trivial conflict with commit a74bd1ad7a:
    "Convert to using %pOFn instead of device_node.name"

Reported-by: Marek Vasut <marex@denx.de>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/clocksource/dw_apb_timer_of.c b/drivers/clocksource/dw_apb_timer_of.c
index fabaa29cc3a4fbd6c2c47d94100dc3200ac20557..db410acd8964cf25008573a2b267cf933aaff3ac 100644 (file)
--- a/drivers/clocksource/dw_apb_timer_of.c
+++ b/drivers/clocksource/dw_apb_timer_of.c
@@ -22,6 +22,7 @@
 #include <linux/of_address.h>
 #include <linux/of_irq.h>
 #include <linux/clk.h>
+#include <linux/reset.h>
 #include <linux/sched_clock.h>
 
 static void __init timer_get_base_and_rate(struct device_node *np,
@@ -29,12 +30,23 @@ static void __init timer_get_base_and_rate(struct device_node *np,
 {
        struct clk *timer_clk;
        struct clk *pclk;
+       struct reset_control *rstc;
 
        *base = of_iomap(np, 0);
 
        if (!*base)
                panic("Unable to map regs for %pOFn", np);
 
+       /*
+        * Reset the timer if the reset control is available, wiping
+        * out the state the firmware may have left it
+        */
+       rstc = of_reset_control_get(np, NULL);
+       if (!IS_ERR(rstc)) {
+               reset_control_assert(rstc);
+               reset_control_deassert(rstc);
+       }
+
        /*
         * Not all implementations use a periphal clock, so don't panic
         * if it's not present