[Backport for linux-5.10.y PATCH 1/2] clocksource/drivers/timer-ti-dm: Prepare to handle dra7 timer wrap issue

[Backport for linux-5.10.y PATCH 1/2] clocksource/drivers/timer-ti-dm: Prepare to handle dra7 timer wrap issue

[Tony Lindgren]

Upstream commit 3efe7a878a11c13b5297057bfc1e5639ce1241ce. Updated to
apply to stable linux-5.10.y without need for upstream typo fix commit
4bf07f6562a01a488877e05267808da7147f44a5. Needed to avoid duplicate
code for upstream commit 25de4ce5ed02994aea8bc111d133308f6fd62566.

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 timers instead.

Let's prepare for adding support for percpu timers by adding a common
dmtimer_clkevt_init_common() and call it from dmtimer_clockevent_init().
This patch makes no intentional functional changes.

Signed-off-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20210323074326.28302-2-tony@atomide.com
---
 drivers/clocksource/timer-ti-dm-systimer.c | 68 ++++++++++++++--------
 1 file changed, 44 insertions(+), 24 deletions(-)

diff --git a/drivers/clocksource/timer-ti-dm-systimer.c b/drivers/clocksource/timer-ti-dm-systimer.c
--- a/drivers/clocksource/timer-ti-dm-systimer.c
+++ b/drivers/clocksource/timer-ti-dm-systimer.c
@@ -530,17 +530,17 @@ static void omap_clockevent_unidle(struct clock_event_device *evt)
 	writel_relaxed(OMAP_TIMER_INT_OVERFLOW, t->base + t->wakeup);
 }
 
-static int __init dmtimer_clockevent_init(struct device_node *np)
+static int __init dmtimer_clkevt_init_common(struct dmtimer_clockevent *clkevt,
+					     struct device_node *np,
+					     unsigned int features,
+					     const struct cpumask *cpumask,
+					     const char *name,
+					     int rating)
 {
-	struct dmtimer_clockevent *clkevt;
 	struct clock_event_device *dev;
 	struct dmtimer_systimer *t;
 	int error;
 
-	clkevt = kzalloc(sizeof(*clkevt), GFP_KERNEL);
-	if (!clkevt)
-		return -ENOMEM;
-
 	t = &clkevt->t;
 	dev = &clkevt->dev;
 
@@ -548,25 +548,23 @@ static int __init dmtimer_clockevent_init(struct device_node *np)
 	 * We mostly use cpuidle_coupled with ARM local timers for runtime,
 	 * so there's probably no use for CLOCK_EVT_FEAT_DYNIRQ here.
 	 */
-	dev->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
-	dev->rating = 300;
+	dev->features = features;
+	dev->rating = rating;
 	dev->set_next_event = dmtimer_set_next_event;
 	dev->set_state_shutdown = dmtimer_clockevent_shutdown;
 	dev->set_state_periodic = dmtimer_set_periodic;
 	dev->set_state_oneshot = dmtimer_clockevent_shutdown;
 	dev->set_state_oneshot_stopped = dmtimer_clockevent_shutdown;
 	dev->tick_resume = dmtimer_clockevent_shutdown;
-	dev->cpumask = cpu_possible_mask;
+	dev->cpumask = cpumask;
 
 	dev->irq = irq_of_parse_and_map(np, 0);
-	if (!dev->irq) {
-		error = -ENXIO;
-		goto err_out_free;
-	}
+	if (!dev->irq)
+		return -ENXIO;
 
 	error = dmtimer_systimer_setup(np, &clkevt->t);
 	if (error)
-		goto err_out_free;
+		return error;
 
 	clkevt->period = 0xffffffff - DIV_ROUND_CLOSEST(t->rate, HZ);
 
@@ -578,32 +576,54 @@ static int __init dmtimer_clockevent_init(struct device_node *np)
 	writel_relaxed(OMAP_TIMER_CTRL_POSTED, t->base + t->ifctrl);
 
 	error = request_irq(dev->irq, dmtimer_clockevent_interrupt,
-			    IRQF_TIMER, "clockevent", clkevt);
+			    IRQF_TIMER, name, clkevt);
 	if (error)
 		goto err_out_unmap;
 
 	writel_relaxed(OMAP_TIMER_INT_OVERFLOW, t->base + t->irq_ena);
 	writel_relaxed(OMAP_TIMER_INT_OVERFLOW, t->base + t->wakeup);
 
-	pr_info("TI gptimer clockevent: %s%lu Hz at %pOF\n",
-		of_find_property(np, "ti,timer-alwon", NULL) ?
+	pr_info("TI gptimer %s: %s%lu Hz at %pOF\n",
+		name, of_find_property(np, "ti,timer-alwon", NULL) ?
 		"always-on " : "", t->rate, np->parent);
 
-	clockevents_config_and_register(dev, t->rate,
-					3, /* Timer internal resynch latency */
+	return 0;
+
+err_out_unmap:
+	iounmap(t->base);
+
+	return error;
+}
+
+static int __init dmtimer_clockevent_init(struct device_node *np)
+{
+	struct dmtimer_clockevent *clkevt;
+	int error;
+
+	clkevt = kzalloc(sizeof(*clkevt), GFP_KERNEL);
+	if (!clkevt)
+		return -ENOMEM;
+
+	error = dmtimer_clkevt_init_common(clkevt, np,
+					   CLOCK_EVT_FEAT_PERIODIC |
+					   CLOCK_EVT_FEAT_ONESHOT,
+					   cpu_possible_mask, "clockevent",
+					   300);
+	if (error)
+		goto err_out_free;
+
+	clockevents_config_and_register(&clkevt->dev, clkevt->t.rate,
+					3, /* Timer internal resync latency */
 					0xffffffff);
 
 	if (of_machine_is_compatible("ti,am33xx") ||
 	    of_machine_is_compatible("ti,am43")) {
-		dev->suspend = omap_clockevent_idle;
-		dev->resume = omap_clockevent_unidle;
+		clkevt->dev.suspend = omap_clockevent_idle;
+		clkevt->dev.resume = omap_clockevent_unidle;
 	}
 
 	return 0;
 
-err_out_unmap:
-	iounmap(t->base);
-
 err_out_free:
 	kfree(clkevt);
 
-- 
2.31.1

[Backport for linux-5.10.y PATCH 2/2] clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940

[Tony Lindgren]

Upstream commit 25de4ce5ed02994aea8bc111d133308f6fd62566 for stable
linux-5.10.y. Depends on backported upstream commit
3efe7a878a11c13b5297057bfc1e5639ce1241ce.

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
---
 arch/arm/boot/dts/dra7-l4.dtsi             |  4 +-
 arch/arm/boot/dts/dra7.dtsi                | 20 ++++++
 drivers/clocksource/timer-ti-dm-systimer.c | 76 ++++++++++++++++++++++
 include/linux/cpuhotplug.h                 |  1 +
 4 files changed, 99 insertions(+), 2 deletions(-)

diff --git a/arch/arm/boot/dts/dra7-l4.dtsi b/arch/arm/boot/dts/dra7-l4.dtsi
--- a/arch/arm/boot/dts/dra7-l4.dtsi
+++ b/arch/arm/boot/dts/dra7-l4.dtsi
@@ -1168,7 +1168,7 @@ timer2: timer@0 {
 			};
 		};
 
-		target-module@34000 {			/* 0x48034000, ap 7 46.0 */
+		timer3_target: target-module@34000 {	/* 0x48034000, ap 7 46.0 */
 			compatible = "ti,sysc-omap4-timer", "ti,sysc";
 			reg = <0x34000 0x4>,
 			      <0x34010 0x4>;
@@ -1195,7 +1195,7 @@ timer3: timer@0 {
 			};
 		};
 
-		target-module@36000 {			/* 0x48036000, ap 9 4e.0 */
+		timer4_target: target-module@36000 {	/* 0x48036000, ap 9 4e.0 */
 			compatible = "ti,sysc-omap4-timer", "ti,sysc";
 			reg = <0x36000 0x4>,
 			      <0x36010 0x4>;
diff --git a/arch/arm/boot/dts/dra7.dtsi b/arch/arm/boot/dts/dra7.dtsi
--- a/arch/arm/boot/dts/dra7.dtsi
+++ b/arch/arm/boot/dts/dra7.dtsi
@@ -46,6 +46,7 @@ aliases {
 
 	timer {
 		compatible = "arm,armv7-timer";
+		status = "disabled";	/* See ARM architected timer wrap erratum i940 */
 		interrupts = <GIC_PPI 13 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>,
 			     <GIC_PPI 14 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>,
 			     <GIC_PPI 11 (GIC_CPU_MASK_SIMPLE(2) | IRQ_TYPE_LEVEL_LOW)>,
@@ -1090,3 +1091,22 @@ timer@0 {
 		assigned-clock-parents = <&sys_32k_ck>;
 	};
 };
+
+/* Local timers, see ARM architected timer wrap erratum i940 */
+&timer3_target {
+	ti,no-reset-on-init;
+	ti,no-idle;
+	timer@0 {
+		assigned-clocks = <&l4per_clkctrl DRA7_L4PER_TIMER3_CLKCTRL 24>;
+		assigned-clock-parents = <&timer_sys_clk_div>;
+	};
+};
+
+&timer4_target {
+	ti,no-reset-on-init;
+	ti,no-idle;
+	timer@0 {
+		assigned-clocks = <&l4per_clkctrl DRA7_L4PER_TIMER4_CLKCTRL 24>;
+		assigned-clock-parents = <&timer_sys_clk_div>;
+	};
+};
diff --git a/drivers/clocksource/timer-ti-dm-systimer.c b/drivers/clocksource/timer-ti-dm-systimer.c
--- 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 @@ static int __init dmtimer_clockevent_init(struct device_node *np)
 	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;
 }
 
diff --git a/include/linux/cpuhotplug.h b/include/linux/cpuhotplug.h
--- a/include/linux/cpuhotplug.h
+++ b/include/linux/cpuhotplug.h
@@ -135,6 +135,7 @@ enum cpuhp_state {
 	CPUHP_AP_RISCV_TIMER_STARTING,
 	CPUHP_AP_CLINT_TIMER_STARTING,
 	CPUHP_AP_CSKY_TIMER_STARTING,
+	CPUHP_AP_TI_GP_TIMER_STARTING,
 	CPUHP_AP_HYPERV_TIMER_STARTING,
 	CPUHP_AP_KVM_STARTING,
 	CPUHP_AP_KVM_ARM_VGIC_INIT_STARTING,
-- 
2.31.1

Re: [Backport for linux-5.10.y PATCH 2/2] clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940

[Tony Lindgren]

* Tony Lindgren <tony@atomide.com> [210517 08:23]:
> Upstream commit 25de4ce5ed02994aea8bc111d133308f6fd62566 for stable
> linux-5.10.y. Depends on backported upstream commit
> 3efe7a878a11c13b5297057bfc1e5639ce1241ce.
> 
> 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.

FYI, these patches also apply to linux-5.11.y and linux-5.12.y. This
patch applies with fuzz to the related device tree changes though,
so please let me know if separate patches are needed.

Regards,

Tony

Re: [Backport for linux-5.10.y PATCH 2/2] clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940

[Greg KH]

On Mon, May 17, 2021 at 11:42:26AM +0300, Tony Lindgren wrote:
> * Tony Lindgren <tony@atomide.com> [210517 08:23]:
> > Upstream commit 25de4ce5ed02994aea8bc111d133308f6fd62566 for stable
> > linux-5.10.y. Depends on backported upstream commit
> > 3efe7a878a11c13b5297057bfc1e5639ce1241ce.
> > 
> > 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.
> 
> FYI, these patches also apply to linux-5.11.y and linux-5.12.y. This
> patch applies with fuzz to the related device tree changes though,
> so please let me know if separate patches are needed.

All now queued up, thanks.

greg k-h