On 04/03/2021 08:37, Tony Lindgren wrote: > 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. Cc: <stable@xxxxxxxxxxxxxxx> # v5.8+ ?? > 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@xxxxxx> > Cc: Tero Kristo <kristo@xxxxxxxxxx> > Signed-off-by: Tony Lindgren <tony@xxxxxxxxxxx> > --- > 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)>, > @@ -1241,3 +1242,22 @@ 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> > @@ -634,6 +635,78 @@ 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) > @@ -767,6 +840,9 @@ 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, > -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
