clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940

commit 25de4ce5ed02994aea8bc111d133308f6fd62566 upstream.

There is a timer wrap issue on dra7 for the ARM architected timer.
In a typical clock configuration the timer fails to wrap after 388 days.

To work around the issue, we need to use timer-ti-dm percpu timers instead.

Let's configure dmtimer3 and 4 as percpu timers by default, and warn about
the issue if the dtb is not configured properly.

For more information, please see the errata for "AM572x Sitara Processors
Silicon Revisions 1.1, 2.0":

https://www.ti.com/lit/er/sprz429m/sprz429m.pdf

The concept is based on earlier reference patches done by Tero Kristo and
Keerthy.

Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
Cc: Keerthy <j-keerthy@ti.com>
Cc: Tero Kristo <kristo@kernel.org>
[tony@atomide.com: backported to 5.4.y]
Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 54 insertions, 3 deletions

diff --git a/arch/arm/mach-omap2/board-generic.c b/arch/arm/mach-omap2/board-generic.c
index ff992f8895ee..ad512f07d568 100644
--- a/arch/arm/mach-omap2/board-generic.c
+++ b/arch/arm/mach-omap2/board-generic.c
@@ -327,7 +327,7 @@ DT_MACHINE_START(DRA74X_DT, "Generic DRA74X (Flattened Device Tree)")
 	.init_late	= dra7xx_init_late,
 	.init_irq	= omap_gic_of_init,
 	.init_machine	= omap_generic_init,
-	.init_time	= omap5_realtime_timer_init,
+	.init_time	= omap3_gptimer_timer_init,
 	.dt_compat	= dra74x_boards_compat,
 	.restart	= omap44xx_restart,
 MACHINE_END
@@ -350,7 +350,7 @@ DT_MACHINE_START(DRA72X_DT, "Generic DRA72X (Flattened Device Tree)")
 	.init_late	= dra7xx_init_late,
 	.init_irq	= omap_gic_of_init,
 	.init_machine	= omap_generic_init,
-	.init_time	= omap5_realtime_timer_init,
+	.init_time	= omap3_gptimer_timer_init,
 	.dt_compat	= dra72x_boards_compat,
 	.restart	= omap44xx_restart,
 MACHINE_END
diff --git a/arch/arm/mach-omap2/timer.c b/arch/arm/mach-omap2/timer.c
index b92cb1e60358..1defb838eae3 100644
--- a/arch/arm/mach-omap2/timer.c
+++ b/arch/arm/mach-omap2/timer.c
@@ -42,6 +42,7 @@
 #include <linux/platform_device.h>
 #include <linux/platform_data/dmtimer-omap.h>
 #include <linux/sched_clock.h>
+#include <linux/cpu.h>
 
 #include <asm/mach/time.h>
 
@@ -420,6 +421,53 @@ static void __init dmtimer_clkevt_init_common(struct dmtimer_clockevent *clkevt,
 		timer->rate);
 }
 
+static DEFINE_PER_CPU(struct dmtimer_clockevent, dmtimer_percpu_timer);
+
+static int omap_gptimer_starting_cpu(unsigned int cpu)
+{
+	struct dmtimer_clockevent *clkevt = per_cpu_ptr(&dmtimer_percpu_timer, cpu);
+	struct clock_event_device *dev = &clkevt->dev;
+	struct omap_dm_timer *timer = &clkevt->timer;
+
+	clockevents_config_and_register(dev, timer->rate, 3, ULONG_MAX);
+	irq_force_affinity(dev->irq, cpumask_of(cpu));
+
+	return 0;
+}
+
+static int __init dmtimer_percpu_quirk_init(void)
+{
+	struct dmtimer_clockevent *clkevt;
+	struct clock_event_device *dev;
+	struct device_node *arm_timer;
+	struct omap_dm_timer *timer;
+	int cpu = 0;
+
+	arm_timer = of_find_compatible_node(NULL, NULL, "arm,armv7-timer");
+	if (of_device_is_available(arm_timer)) {
+		pr_warn_once("ARM architected timer wrap issue i940 detected\n");
+		return 0;
+	}
+
+	for_each_possible_cpu(cpu) {
+		clkevt = per_cpu_ptr(&dmtimer_percpu_timer, cpu);
+		dev = &clkevt->dev;
+		timer = &clkevt->timer;
+
+		dmtimer_clkevt_init_common(clkevt, 0, "timer_sys_ck",
+					   CLOCK_EVT_FEAT_ONESHOT,
+					   cpumask_of(cpu),
+					   "assigned-clock-parents",
+					   500, "percpu timer");
+	}
+
+	cpuhp_setup_state(CPUHP_AP_OMAP_DM_TIMER_STARTING,
+			  "clockevents/omap/gptimer:starting",
+			  omap_gptimer_starting_cpu, NULL);
+
+	return 0;
+}
+
 /* Clocksource code */
 static struct omap_dm_timer clksrc;
 static bool use_gptimer_clksrc __initdata;
@@ -564,6 +612,9 @@ static void __init __omap_sync32k_timer_init(int clkev_nr, const char *clkev_src
 					3, /* Timer internal resynch latency */
 					0xffffffff);
 
+	if (soc_is_dra7xx())
+		dmtimer_percpu_quirk_init();
+
 	/* Enable the use of clocksource="gp_timer" kernel parameter */
 	if (use_gptimer_clksrc || gptimer)
 		omap2_gptimer_clocksource_init(clksrc_nr, clksrc_src,
@@ -591,7 +642,7 @@ void __init omap3_secure_sync32k_timer_init(void)
 #endif /* CONFIG_ARCH_OMAP3 */
 
 #if defined(CONFIG_ARCH_OMAP3) || defined(CONFIG_SOC_AM33XX) || \
-	defined(CONFIG_SOC_AM43XX)
+	defined(CONFIG_SOC_AM43XX) || defined(CONFIG_SOC_DRA7XX)
 void __init omap3_gptimer_timer_init(void)
 {
 	__omap_sync32k_timer_init(2, "timer_sys_ck", NULL,