clocksource/drivers/timer-ti-dm: Fix suspend and resume for am3 and am4

Carlos Hernandez <ceh@ti.com> reported that we now have a suspend and
resume regresssion on am3 and am4 compared to the earlier kernels. While
suspend and resume works with v5.8-rc3, we now get errors with rtcwake:

pm33xx pm33xx: PM: Could not transition all powerdomains to target state
...
rtcwake: write error

This is because we now fail to idle the system timer clocks that the
idle code checks and the error gets propagated to the rtcwake.

Turns out there are several issues that need to be fixed:

1. Ignore no-idle and no-reset configured timers for the ti-sysc
   interconnect target driver as otherwise it will keep the system timer
   clocks enabled

2. Toggle the system timer functional clock for suspend for am3 and am4
   (but not for clocksource on am3)

3. Only reconfigure type1 timers in dmtimer_systimer_disable()

4. Use of_machine_is_compatible() instead of of_device_is_compatible()
   for checking the SoC type

Fixes: 52762fbd1c47 ("clocksource/drivers/timer-ti-dm: Add clockevent and clocksource support")
Reported-by: Carlos Hernandez <ceh@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>
Tested-by: Carlos Hernandez <ceh@ti.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200713162601.6829-1-tony@atomide.com

1 files changed, 22 insertions, 0 deletions

diff --git a/drivers/bus/ti-sysc.c b/drivers/bus/ti-sysc.c
index bb54fb514e40..c6427d0bc94c 100644
--- a/drivers/bus/ti-sysc.c
+++ b/drivers/bus/ti-sysc.c
@@ -2864,6 +2864,24 @@ static int sysc_check_disabled_devices(struct sysc *ddata)
 	return error;
 }
 
+/*
+ * Ignore timers tagged with no-reset and no-idle. These are likely in use,
+ * for example by drivers/clocksource/timer-ti-dm-systimer.c. If more checks
+ * are needed, we could also look at the timer register configuration.
+ */
+static int sysc_check_active_timer(struct sysc *ddata)
+{
+	if (ddata->cap->type != TI_SYSC_OMAP2_TIMER &&
+	    ddata->cap->type != TI_SYSC_OMAP4_TIMER)
+		return 0;
+
+	if ((ddata->cfg.quirks & SYSC_QUIRK_NO_RESET_ON_INIT) &&
+	    (ddata->cfg.quirks & SYSC_QUIRK_NO_IDLE))
+		return -EBUSY;
+
+	return 0;
+}
+
 static const struct of_device_id sysc_match_table[] = {
 	{ .compatible = "simple-bus", },
 	{ /* sentinel */ },
@@ -2920,6 +2938,10 @@ static int sysc_probe(struct platform_device *pdev)
 	if (error)
 		return error;
 
+	error = sysc_check_active_timer(ddata);
+	if (error)
+		return error;
+
 	error = sysc_get_clocks(ddata);
 	if (error)
 		return error;