clocksource: timer-ti-dm: Fix pwm dmtimer usage of fck reparenting

[ Upstream commit 983a5a4 ]

Commit 84badc5 ("ARM: dts: omap4: Move l4 child devices to probe
them with ti-sysc") moved some omap4 timers to probe with ti-sysc
interconnect target module. Turns out this broke pwm-omap-dmtimer
where we now try to reparent the clock to itself with the following:

omap_dm_timer_of_set_source: failed to set parent

With ti-sysc, we can now configure the clock sources in the dts
with assigned-clocks and assigned-clock-parents. So we should be able
to remove omap_dm_timer_of_set_source with clean-up patches later on.
But for now, let's just fix it first by checking if parent and fck
are the same and bail out of so.

Fixes: 84badc5 ("ARM: dts: omap4: Move l4 child devices to probe them with ti-sysc")
Cc: Bartosz Golaszewski <[email protected]>
Cc: Daniel Lezcano <[email protected]>
Cc: H. Nikolaus Schaller <[email protected]>
Cc: Keerthy <[email protected]>
Cc: Ladislav Michl <[email protected]>
Cc: Pavel Machek <[email protected]>
Cc: Sebastian Reichel <[email protected]>
Cc: Tero Kristo <[email protected]>
Cc: Thierry Reding <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Reported-by: H. Nikolaus Schaller <[email protected]>
Tested-By: Andreas Kemnade <[email protected]>
Tested-By: H. Nikolaus Schaller <[email protected]>
Signed-off-by: Tony Lindgren <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>

drivers/clocksource/timer-ti-dm.c

@@ -154,6 +154,10 @@ static int omap_dm_timer_of_set_source(struct omap_dm_timer *timer)
 	if (IS_ERR(parent))
 		return -ENODEV;
 
+	/* Bail out if both clocks point to fck */
+	if (clk_is_match(parent, timer->fclk))
+		return 0;
+
 	ret = clk_set_parent(timer->fclk, parent);
 	if (ret < 0)
 		pr_err("%s: failed to set parent\n", __func__);