ARM: dts: Fix timer regression for beagleboard revision c

Commit e428e25 ("ARM: dts: Configure system timers for omap3")
caused a timer regression for beagleboard revision c where the system
clockevent stops working if omap3isp module is unloaded.

Turns out we still have beagleboard revisions a-b4 capacitor c70 quirks
applied that limit the usable timers for no good reason. This also affects
the power management as we use the system clock instead of the 32k clock
source.

Let's fix the issue by adding a new omap3-beagle-ab4.dts for the old timer
quirks. This allows us to remove the timer quirks for later beagleboard
revisions. We also need to update the related timer quirk check for the
correct compatible property.

Fixes: e428e25 ("ARM: dts: Configure system timers for omap3")
Cc: linux-kernel@vger.kernel.org
Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rob Herring <robh+dt@kernel.org>
Reported-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Tested-by: Jarkko Nikula <jarkko.nikula@bitmer.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

Documentation/devicetree/bindings/arm/omap/omap.txt

@@ -119,6 +119,9 @@ Boards (incomplete list of examples):
 - OMAP3 BeagleBoard : Low cost community board
   compatible = "ti,omap3-beagle", "ti,omap3430", "ti,omap3"
 
+- OMAP3 BeagleBoard A to B4 : Early BeagleBoard revisions A to B4 with a timer quirk
+  compatible = "ti,omap3-beagle-ab4", "ti,omap3-beagle", "ti,omap3430", "ti,omap3"
+
 - OMAP3 Tobi with Overo : Commercial expansion board with daughter board
   compatible = "gumstix,omap3-overo-tobi", "gumstix,omap3-overo", "ti,omap3430", "ti,omap3"
 

arch/arm/boot/dts/Makefile

@@ -794,6 +794,7 @@ dtb-$(CONFIG_ARCH_OMAP3) += \
 	logicpd-som-lv-37xx-devkit.dtb \
 	omap3430-sdp.dtb \
 	omap3-beagle.dtb \
+	omap3-beagle-ab4.dtb \
 	omap3-beagle-xm.dtb \
 	omap3-beagle-xm-ab.dtb \
 	omap3-cm-t3517.dtb \

arch/arm/boot/dts/omap3-beagle-ab4.dts

@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/dts-v1/;
+
+#include "omap3-beagle.dts"
+
+/ {
+	model = "TI OMAP3 BeagleBoard A to B4";
+	compatible = "ti,omap3-beagle-ab4", "ti,omap3-beagle", "ti,omap3430", "ti,omap3";
+};
+
+/*
+ * Workaround for capacitor C70 issue, see "Boards revision A and < B5"
+ * section at https://elinux.org/BeagleBoard_Community
+ */
+
+/* Unusable as clocksource because of unreliable oscillator */
+&counter32k {
+	status = "disabled";
+};
+
+/* Unusable as clockevent because of unreliable oscillator, allow to idle */
+&timer1_target {
+	/delete-property/ti,no-reset-on-init;
+	/delete-property/ti,no-idle;
+	timer@0 {
+		/delete-property/ti,timer-alwon;
+	};
+};
+
+/* Preferred always-on timer for clocksource */
+&timer12_target {
+	ti,no-reset-on-init;
+	ti,no-idle;
+	timer@0 {
+		/* Always clocked by secure_32k_fck */
+	};
+};
+
+/* Preferred timer for clockevent */
+&timer2_target {
+	ti,no-reset-on-init;
+	ti,no-idle;
+	timer@0 {
+		assigned-clocks = <&gpt2_fck>;
+		assigned-clock-parents = <&sys_ck>;
+	};
+};

arch/arm/boot/dts/omap3-beagle.dts

@@ -304,39 +304,6 @@
 	phys = <0 &hsusb2_phy>;
 };
 
-/* Unusable as clocksource because of unreliable oscillator */
-&counter32k {
-	status = "disabled";
-};
-
-/* Unusable as clockevent because if unreliable oscillator, allow to idle */
-&timer1_target {
-	/delete-property/ti,no-reset-on-init;
-	/delete-property/ti,no-idle;
-	timer@0 {
-		/delete-property/ti,timer-alwon;
-	};
-};
-
-/* Preferred always-on timer for clocksource */
-&timer12_target {
-	ti,no-reset-on-init;
-	ti,no-idle;
-	timer@0 {
-		/* Always clocked by secure_32k_fck */
-	};
-};
-
-/* Preferred timer for clockevent */
-&timer2_target {
-	ti,no-reset-on-init;
-	ti,no-idle;
-	timer@0 {
-		assigned-clocks = <&gpt2_fck>;
-		assigned-clock-parents = <&sys_ck>;
-	};
-};
-
 &twl_gpio {
 	ti,use-leds;
 	/* pullups: BIT(1) */

drivers/clocksource/timer-ti-dm-systimer.c

@@ -241,7 +241,7 @@ static void __init dmtimer_systimer_assign_alwon(void)
 	bool quirk_unreliable_oscillator = false;
 
 	/* Quirk unreliable 32 KiHz oscillator with incomplete dts */
-	if (of_machine_is_compatible("ti,omap3-beagle") ||
+	if (of_machine_is_compatible("ti,omap3-beagle-ab4") ||
 	    of_machine_is_compatible("timll,omap3-devkit8000")) {
 		quirk_unreliable_oscillator = true;
 		counter_32k = -ENODEV;