clocksource: atmel-st: get and use slow clock

The current slow clock rate is hardcoded. Properly get the slow clock
and use its rate.

Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>

diff --git a/drivers/clocksource/timer-atmel-st.c b/drivers/clocksource/timer-atmel-st.c
index 41b7b6d..29d21d6 100644 (file)
--- a/drivers/clocksource/timer-atmel-st.c
+++ b/drivers/clocksource/timer-atmel-st.c
@@ -22,6 +22,7 @@
 #include <linux/kernel.h>
 #include <linux/interrupt.h>
 #include <linux/irq.h>
+#include <linux/clk.h>
 #include <linux/clockchips.h>
 #include <linux/export.h>
 #include <linux/mfd/syscon.h>
@@ -33,9 +34,7 @@ static unsigned long last_crtr;
 static u32 irqmask;
 static struct clock_event_device clkevt;
 static struct regmap *regmap_st;
-
-#define AT91_SLOW_CLOCK                32768
-#define RM9200_TIMER_LATCH     ((AT91_SLOW_CLOCK + HZ/2) / HZ)
+static int timer_latch;
 
 /*
  * The ST_CRTR is updated asynchronously to the master clock ... but
@@ -82,8 +81,8 @@ static irqreturn_t at91rm9200_timer_interrupt(int irq, void *dev_id)
        if (sr & AT91_ST_PITS) {
                u32     crtr = read_CRTR();
 
-               while (((crtr - last_crtr) & AT91_ST_CRTV) >= RM9200_TIMER_LATCH) {
-                       last_crtr += RM9200_TIMER_LATCH;
+               while (((crtr - last_crtr) & AT91_ST_CRTV) >= timer_latch) {
+                       last_crtr += timer_latch;
                        clkevt.event_handler(&clkevt);
                }
                return IRQ_HANDLED;
@@ -144,7 +143,7 @@ static int clkevt32k_set_periodic(struct clock_event_device *dev)
 
        /* PIT for periodic irqs; fixed rate of 1/HZ */
        irqmask = AT91_ST_PITS;
-       regmap_write(regmap_st, AT91_ST_PIMR, RM9200_TIMER_LATCH);
+       regmap_write(regmap_st, AT91_ST_PIMR, timer_latch);
        regmap_write(regmap_st, AT91_ST_IER, irqmask);
        return 0;
 }
@@ -197,7 +196,8 @@ static struct clock_event_device clkevt = {
  */
 static void __init atmel_st_timer_init(struct device_node *node)
 {
-       unsigned int val;
+       struct clk *sclk;
+       unsigned int sclk_rate, val;
        int irq, ret;
 
        regmap_st = syscon_node_to_regmap(node);
@@ -221,6 +221,19 @@ static void __init atmel_st_timer_init(struct device_node *node)
        if (ret)
                panic(pr_fmt("Unable to setup IRQ\n"));
 
+       sclk = of_clk_get(node, 0);
+       if (IS_ERR(sclk))
+               panic(pr_fmt("Unable to get slow clock\n"));
+
+       clk_prepare_enable(sclk);
+       if (ret)
+               panic(pr_fmt("Could not enable slow clock\n"));
+
+       sclk_rate = clk_get_rate(sclk);
+       if (!sclk_rate)
+               panic(pr_fmt("Invalid slow clock rate\n"));
+       timer_latch = (sclk_rate + HZ / 2) / HZ;
+
        /* The 32KiHz "Slow Clock" (tick every 30517.58 nanoseconds) is used
         * directly for the clocksource and all clockevents, after adjusting
         * its prescaler from the 1 Hz default.
@@ -229,11 +242,11 @@ static void __init atmel_st_timer_init(struct device_node *node)
 
        /* Setup timer clockevent, with minimum of two ticks (important!!) */
        clkevt.cpumask = cpumask_of(0);
-       clockevents_config_and_register(&clkevt, AT91_SLOW_CLOCK,
+       clockevents_config_and_register(&clkevt, sclk_rate,
                                        2, AT91_ST_ALMV);
 
        /* register clocksource */
-       clocksource_register_hz(&clk32k, AT91_SLOW_CLOCK);
+       clocksource_register_hz(&clk32k, sclk_rate);
 }
 CLOCKSOURCE_OF_DECLARE(atmel_st_timer, "atmel,at91rm9200-st",
                       atmel_st_timer_init);