[tip: timers/core] clocksource/drivers/exynos_mct: Support frc-shared property

[tip-bot2 for Vincent Whitchurch]

The following commit has been merged into the timers/core branch of tip:

Commit-ID:     e8550f0e7bde9bd31697e3c534d386f7f3b5787b
Gitweb:        https://git.kernel.org/tip/e8550f0e7bde9bd31697e3c534d386f7f3b5787b
Author:        Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
AuthorDate:    Thu, 09 Jun 2022 13:27:36 +02:00
Committer:     Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
CommitterDate: Tue, 20 Sep 2022 10:49:45 +02:00

clocksource/drivers/exynos_mct: Support frc-shared property

When the FRC is shared with another main processor, the other processor
is assumed to have started it and this processor should not write to the
global registers.

Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
Signed-off-by: Vincent Whitchurch <vincent.whitchurch@xxxxxxxx>
Link: https://lore.kernel.org/r/20220609112738.359385-3-vincent.whitchurch@xxxxxxxx
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
---
 drivers/clocksource/exynos_mct.c | 21 ++++++++++++++++++---
 1 file changed, 18 insertions(+), 3 deletions(-)

diff --git a/drivers/clocksource/exynos_mct.c b/drivers/clocksource/exynos_mct.c
index f29c812..1202383 100644
--- a/drivers/clocksource/exynos_mct.c
+++ b/drivers/clocksource/exynos_mct.c
@@ -233,9 +233,16 @@ static cycles_t exynos4_read_current_timer(void)
 }
 #endif
 
-static int __init exynos4_clocksource_init(void)
+static int __init exynos4_clocksource_init(bool frc_shared)
 {
-	exynos4_mct_frc_start();
+	/*
+	 * When the frc is shared, the main processer should have already
+	 * turned it on and we shouldn't be writing to TCON.
+	 */
+	if (frc_shared)
+		mct_frc.resume = NULL;
+	else
+		exynos4_mct_frc_start();
 
 #if defined(CONFIG_ARM)
 	exynos4_delay_timer.read_current_timer = &exynos4_read_current_timer;
@@ -605,6 +612,7 @@ out_irq:
 
 static int __init mct_init_dt(struct device_node *np, unsigned int int_type)
 {
+	bool frc_shared = of_property_read_bool(np, "samsung,frc-shared");
 	int ret;
 
 	ret = exynos4_timer_resources(np);
@@ -615,10 +623,17 @@ static int __init mct_init_dt(struct device_node *np, unsigned int int_type)
 	if (ret)
 		return ret;
 
-	ret = exynos4_clocksource_init();
+	ret = exynos4_clocksource_init(frc_shared);
 	if (ret)
 		return ret;
 
+	/*
+	 * When the FRC is shared with a main processor, this secondary
+	 * processor cannot use the global comparator.
+	 */
+	if (frc_shared)
+		return ret;
+
 	return exynos4_clockevent_init();
 }