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authorTony Lindgren <tony@atomide.com>2021-03-23 09:43:26 +0200
committerDaniel Lezcano <daniel.lezcano@linaro.org>2021-04-08 16:41:18 +0200
commit25de4ce5ed02994aea8bc111d133308f6fd62566 (patch)
tree74bd4c307d545f9caf89b26617d3b8c007bc392d /drivers/clocksource
parent3efe7a878a11c13b5297057bfc1e5639ce1241ce (diff)
clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940
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. Let's do this as a single patch so it can be backported to v5.8 and later kernels easily. Note that this patch depends on earlier timer-ti-dm systimer posted mode fixes, and a preparatory clockevent patch "clocksource/drivers/timer-ti-dm: Prepare to handle dra7 timer wrap issue". 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: Keerthy <j-keerthy@ti.com> Cc: Tero Kristo <kristo@kernel.org> Signed-off-by: Tony Lindgren <tony@atomide.com> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org> Link: https://lore.kernel.org/r/20210323074326.28302-3-tony@atomide.com
Diffstat (limited to 'drivers/clocksource')
-rw-r--r--drivers/clocksource/timer-ti-dm-systimer.c76
1 files changed, 76 insertions, 0 deletions
diff --git a/drivers/clocksource/timer-ti-dm-systimer.c b/drivers/clocksource/timer-ti-dm-systimer.c
index 330803150d85..b6f97960d8ee 100644
--- a/drivers/clocksource/timer-ti-dm-systimer.c
+++ b/drivers/clocksource/timer-ti-dm-systimer.c
@@ -2,6 +2,7 @@
#include <linux/clk.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>
+#include <linux/cpuhotplug.h>
#include <linux/interrupt.h>
#include <linux/io.h>
#include <linux/iopoll.h>
@@ -630,6 +631,78 @@ err_out_free:
return error;
}
+/* Dmtimer as percpu timer. See dra7 ARM architected timer wrap erratum i940 */
+static DEFINE_PER_CPU(struct dmtimer_clockevent, dmtimer_percpu_timer);
+
+static int __init dmtimer_percpu_timer_init(struct device_node *np, int cpu)
+{
+ struct dmtimer_clockevent *clkevt;
+ int error;
+
+ if (!cpu_possible(cpu))
+ return -EINVAL;
+
+ if (!of_property_read_bool(np->parent, "ti,no-reset-on-init") ||
+ !of_property_read_bool(np->parent, "ti,no-idle"))
+ pr_warn("Incomplete dtb for percpu dmtimer %pOF\n", np->parent);
+
+ clkevt = per_cpu_ptr(&dmtimer_percpu_timer, cpu);
+
+ error = dmtimer_clkevt_init_common(clkevt, np, CLOCK_EVT_FEAT_ONESHOT,
+ cpumask_of(cpu), "percpu-dmtimer",
+ 500);
+ if (error)
+ return error;
+
+ return 0;
+}
+
+/* See TRM for timer internal resynch latency */
+static int omap_dmtimer_starting_cpu(unsigned int cpu)
+{
+ struct dmtimer_clockevent *clkevt = per_cpu_ptr(&dmtimer_percpu_timer, cpu);
+ struct clock_event_device *dev = &clkevt->dev;
+ struct dmtimer_systimer *t = &clkevt->t;
+
+ clockevents_config_and_register(dev, t->rate, 3, ULONG_MAX);
+ irq_force_affinity(dev->irq, cpumask_of(cpu));
+
+ return 0;
+}
+
+static int __init dmtimer_percpu_timer_startup(void)
+{
+ struct dmtimer_clockevent *clkevt = per_cpu_ptr(&dmtimer_percpu_timer, 0);
+ struct dmtimer_systimer *t = &clkevt->t;
+
+ if (t->sysc) {
+ cpuhp_setup_state(CPUHP_AP_TI_GP_TIMER_STARTING,
+ "clockevents/omap/gptimer:starting",
+ omap_dmtimer_starting_cpu, NULL);
+ }
+
+ return 0;
+}
+subsys_initcall(dmtimer_percpu_timer_startup);
+
+static int __init dmtimer_percpu_quirk_init(struct device_node *np, u32 pa)
+{
+ struct device_node *arm_timer;
+
+ 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;
+ }
+
+ if (pa == 0x48034000) /* dra7 dmtimer3 */
+ return dmtimer_percpu_timer_init(np, 0);
+ else if (pa == 0x48036000) /* dra7 dmtimer4 */
+ return dmtimer_percpu_timer_init(np, 1);
+
+ return 0;
+}
+
/* Clocksource */
static struct dmtimer_clocksource *
to_dmtimer_clocksource(struct clocksource *cs)
@@ -763,6 +836,9 @@ static int __init dmtimer_systimer_init(struct device_node *np)
if (clockevent == pa)
return dmtimer_clockevent_init(np);
+ if (of_machine_is_compatible("ti,dra7"))
+ return dmtimer_percpu_quirk_init(np, pa);
+
return 0;
}