clocksource/drivers/tcb_clksrc: Register delay timer

Implement and register delay timer to allow get_cycles() to work properly.
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>

drivers/clocksource/Kconfig

@@ -429,7 +429,7 @@ config ATMEL_ST
 
 config ATMEL_TCB_CLKSRC
 	bool "Atmel TC Block timer driver" if COMPILE_TEST
-	depends on HAS_IOMEM
+	depends on ARM && HAS_IOMEM
 	select TIMER_OF if OF
 	help
 	  Support for Timer Counter Blocks on Atmel SoCs.

drivers/clocksource/timer-atmel-tcb.c

@@ -6,6 +6,7 @@
 #include <linux/irq.h>
 
 #include <linux/clk.h>
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/ioport.h>
 #include <linux/io.h>
@@ -125,6 +126,18 @@ static u64 notrace tc_sched_clock_read32(void)
 	return tc_get_cycles32(&clksrc);
 }
 
+static struct delay_timer tc_delay_timer;
+
+static unsigned long tc_delay_timer_read(void)
+{
+	return tc_get_cycles(&clksrc);
+}
+
+static unsigned long notrace tc_delay_timer_read32(void)
+{
+	return tc_get_cycles32(&clksrc);
+}
+
 #ifdef CONFIG_GENERIC_CLOCKEVENTS
 
 struct tc_clkevt_device {
@@ -432,6 +445,7 @@ static int __init tcb_clksrc_init(struct device_node *node)
 		/* setup ony channel 0 */
 		tcb_setup_single_chan(&tc, best_divisor_idx);
 		tc_sched_clock = tc_sched_clock_read32;
+		tc_delay_timer.read_current_timer = tc_delay_timer_read32;
 	} else {
 		/* we have three clocks no matter what the
 		 * underlying platform supports.
@@ -444,6 +458,7 @@ static int __init tcb_clksrc_init(struct device_node *node)
 		/* setup both channel 0 & 1 */
 		tcb_setup_dual_chan(&tc, best_divisor_idx);
 		tc_sched_clock = tc_sched_clock_read;
+		tc_delay_timer.read_current_timer = tc_delay_timer_read;
 	}
 
 	/* and away we go! */
@@ -458,6 +473,9 @@ static int __init tcb_clksrc_init(struct device_node *node)
 
 	sched_clock_register(tc_sched_clock, 32, divided_rate);
 
+	tc_delay_timer.freq = divided_rate;
+	register_current_timer_delay(&tc_delay_timer);
+
 	return 0;
 
 err_unregister_clksrc: