Re: [PATCH v6 4/7] clocksource: Ingenic: Add high resolution timer support for SMP.

[Paul Cercueil <paul@xxxxxxxxxxxxxxx>]

Hi Zhou,


Le ven., févr. 21, 2020 at 00:24, 周琰杰 (Zhou Yanjie) 
<zhouyanjie@xxxxxxxxxxxxxx> a écrit :
> Enable clock event handling on per CPU core basis.
> Make sure that interrupts raised on the first core execute
> event handlers on the correct CPU core.
>
> Tested-by: H. Nikolaus Schaller <hns@xxxxxxxxxxxxx>
> Tested-by: Paul Boddie <paul@xxxxxxxxxxxxx>
> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@xxxxxxxxxxxxxx>
> ---
>
> Notes:
>     v1->v2:
>     1.Adjust function naming to make it more reasonable.
>     2.Replace function smp_call_function_single() with
>       smp_call_function_single_async() in order to resolve
>       the warning below:
>
>     [    0.350942] smp: Brought up 1 node, 2 CPUs
>     [    0.365497] ------------[ cut here ]------------
>     [    0.365522] WARNING: CPU: 0 PID: 1 at kernel/smp.c:300 
> smp_call_function_single+0x110/0x200
>     [    0.365533] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 
> 5.5.0-rc1+ #5
>     [    0.365537] Stack : 00000000 59c73bcd 00000037 80074e80 
> 80000000 80670000 805a0000 80620590
>     [    0.365557]         8065ce38 8fc0dc8c 806d0000 00000000 
> 80670000 00000001 8fc0dc20 59c73bcd
>     [    0.365574]         00000000 00000000 806f0000 80670000 
> 00000000 806dab00 00000000 2d302e35
>     [    0.365591]         203a6d6d 806e0000 806e0000 70617773 
> 80670000 00000000 00000000 00000009
>     [    0.365610]         00000000 8fc94e20 8fc0de30 80690000 
> 00000018 803592dc 00000000 806d0000
>     [    0.365627]         ...
>     [    0.365634] Call Trace:
>     [    0.365647] [<8001b9a0>] show_stack+0x6c/0x12c
>     [    0.365663] [<804aed20>] dump_stack+0x98/0xc8
>     [    0.365673] [<8003044c>] __warn+0xc4/0xe8
>     [    0.365682] [<800304f4>] warn_slowpath_fmt+0x84/0xb8
>     [    0.365690] [<800a886c>] smp_call_function_single+0x110/0x200
>     [    0.365703] ---[ end trace 5785856ca39c79d5 ]---
>     [    0.365557]         8065ce38 8fc0dc8c 806d0000 00000000 
> 80670000 00000001 8fc0dc20 59c73bcd
>     [    0.365574]         00000000 00000000 806f0000 80670000 
> 00000000 806dab00 00000000 2d302e35
>     [    0.365591]         203a6d6d 806e0000 806e0000 70617773 
> 80670000 00000000 00000000 00000009
>     [    0.365610]         00000000 8fc94e20 8fc0de30 80690000 
> 00000018 803592dc 00000000 806d0000
>     [    0.365627]         ...
>     [    0.365634] Call Trace:
>     [    0.365647] [<8001b9a0>] show_stack+0x6c/0x12c
>     [    0.365663] [<804aed20>] dump_stack+0x98/0xc8
>     [    0.365673] [<8003044c>] __warn+0xc4/0xe8
>     [    0.365682] [<800304f4>] warn_slowpath_fmt+0x84/0xb8
>     [    0.365690] [<800a886c>] smp_call_function_single+0x110/0x200
>     [    0.365703] ---[ end trace 5785856ca39c79d5 ]---
>
>     v2->v3:
>     No Change.
>
>     v3->v4:
>     Rebase on top of kernel 5.6-rc1.
>
>     v4->v5:
>     Move the check for (evt->event_handler) from 
> "ingenic_per_cpu_event_handler"
>     to "ingenic_tcu_cevt_cb".
>
>     v5->v6:
>     No change.
>
>  drivers/clocksource/ingenic-timer.c | 113 
> +++++++++++++++++++++++++++++-------
>  1 file changed, 91 insertions(+), 22 deletions(-)
>
> diff --git a/drivers/clocksource/ingenic-timer.c 
> b/drivers/clocksource/ingenic-timer.c
> index 4bbdb3d..e396326 100644
> --- a/drivers/clocksource/ingenic-timer.c
> +++ b/drivers/clocksource/ingenic-timer.c
> @@ -1,7 +1,8 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /*
> - * JZ47xx SoCs TCU IRQ driver
> + * XBurst SoCs TCU IRQ driver
>   * Copyright (C) 2019 Paul Cercueil <paul@xxxxxxxxxxxxxxx>
> + * Copyright (C) 2020 周琰杰 (Zhou Yanjie) 
> <zhouyanjie@xxxxxxxxxxxxxx>
>   */
>
>  #include <linux/bitops.h>
> @@ -21,18 +22,23 @@
>
>  #include <dt-bindings/clock/ingenic,tcu.h>
>
> +static DEFINE_PER_CPU(call_single_data_t, ingenic_cevt_csd);
> +
>  struct ingenic_soc_info {
>  	unsigned int num_channels;
>  };
>
>  struct ingenic_tcu {
>  	struct regmap *map;
> +	struct device_node *np;
>  	struct clk *timer_clk, *cs_clk;
> +	unsigned int timer_local[NR_CPUS];
>  	unsigned int timer_channel, cs_channel;
>  	struct clock_event_device cevt;
>  	struct clocksource cs;
> -	char name[4];
> +	char name[8];
>  	unsigned long pwm_channels_mask;
> +	int cpu;
>  };
>
>  static struct ingenic_tcu *ingenic_tcu;
> @@ -81,6 +87,24 @@ static int ingenic_tcu_cevt_set_next(unsigned long 
> next,
>  	return 0;
>  }
>
> +static void ingenic_per_cpu_event_handler(void *info)
> +{
> +	struct clock_event_device *cevt = (struct clock_event_device *) 
> info;
> +
> +	cevt->event_handler(cevt);
> +}
> +
> +static void ingenic_tcu_per_cpu_cb(struct clock_event_device *evt)
> +{
> +	struct ingenic_tcu *tcu = to_ingenic_tcu(evt);
> +	call_single_data_t *csd;
> +
> +	csd = &per_cpu(ingenic_cevt_csd, tcu->cpu);
> +	csd->info = (void *) evt;
> +	csd->func = ingenic_per_cpu_event_handler;
> +	smp_call_function_single_async(tcu->cpu, csd);
> +}
> +
>  static irqreturn_t ingenic_tcu_cevt_cb(int irq, void *dev_id)
>  {
>  	struct clock_event_device *evt = dev_id;
> @@ -89,7 +113,7 @@ static irqreturn_t ingenic_tcu_cevt_cb(int irq, 
> void *dev_id)
>  	regmap_write(tcu->map, TCU_REG_TECR, BIT(tcu->timer_channel));
>
>  	if (evt->event_handler)
> -		evt->event_handler(evt);
> +		ingenic_tcu_per_cpu_cb(evt);
>
>  	return IRQ_HANDLED;
>  }
> @@ -105,14 +129,21 @@ static struct clk * __init 
> ingenic_tcu_get_clock(struct device_node *np, int id)
>  	return of_clk_get_from_provider(&args);
>  }
>
> -static int __init ingenic_tcu_timer_init(struct device_node *np,
> -					 struct ingenic_tcu *tcu)
> +static int ingenic_tcu_setup_per_cpu_cevt(struct device_node *np,
> +				     unsigned int channel)
>  {
> -	unsigned int timer_virq, channel = tcu->timer_channel;
> +	unsigned int timer_virq;
>  	struct irq_domain *domain;
> +	struct ingenic_tcu *tcu;
>  	unsigned long rate;
>  	int err;
>
> +	tcu = kzalloc(sizeof(*tcu), GFP_KERNEL);
> +	if (!tcu)
> +		return -ENOMEM;
> +
> +	tcu->map = ingenic_tcu->map;
> +
>  	tcu->timer_clk = ingenic_tcu_get_clock(np, channel);
>  	if (IS_ERR(tcu->timer_clk))
>  		return PTR_ERR(tcu->timer_clk);
> @@ -139,13 +170,15 @@ static int __init ingenic_tcu_timer_init(struct 
> device_node *np,
>  		goto err_clk_disable;
>  	}
>
> -	snprintf(tcu->name, sizeof(tcu->name), "TCU");
> +	snprintf(tcu->name, sizeof(tcu->name), "TCU%u", channel);
>
>  	err = request_irq(timer_virq, ingenic_tcu_cevt_cb, IRQF_TIMER,
>  			  tcu->name, &tcu->cevt);
>  	if (err)
>  		goto err_irq_dispose_mapping;
>
> +	tcu->cpu = smp_processor_id();
> +	tcu->timer_channel = channel;
>  	tcu->cevt.cpumask = cpumask_of(smp_processor_id());
>  	tcu->cevt.features = CLOCK_EVT_FEAT_ONESHOT;
>  	tcu->cevt.name = tcu->name;
> @@ -166,6 +199,25 @@ static int __init ingenic_tcu_timer_init(struct 
> device_node *np,
>  	return err;
>  }
>
> +static int ingenic_tcu_setup_cevt(unsigned int cpu)
> +{
> +	int ret;
> +
> +	ret = ingenic_tcu_setup_per_cpu_cevt(ingenic_tcu->np,
> +						ingenic_tcu->timer_local[cpu]);
> +	if (ret)
> +		goto err_tcu_clocksource_cleanup;
> +
> +	return 0;
> +
> +err_tcu_clocksource_cleanup:
> +	clocksource_unregister(&ingenic_tcu->cs);
> +	clk_disable_unprepare(ingenic_tcu->cs_clk);
> +	clk_put(ingenic_tcu->cs_clk);
> +	kfree(ingenic_tcu);
> +	return ret;
> +}
> +
>  static int __init ingenic_tcu_clocksource_init(struct device_node 
> *np,
>  					       struct ingenic_tcu *tcu)
>  {
> @@ -239,6 +291,7 @@ static int __init ingenic_tcu_init(struct 
> device_node *np)
>  	const struct ingenic_soc_info *soc_info = id->data;
>  	struct ingenic_tcu *tcu;
>  	struct regmap *map;
> +	unsigned cpu = 0;
>  	long rate;
>  	int ret;
>
> @@ -252,13 +305,18 @@ static int __init ingenic_tcu_init(struct 
> device_node *np)
>  	if (!tcu)
>  		return -ENOMEM;
>
> -	/* Enable all TCU channels for PWM use by default except channels 
> 0/1 */
> -	tcu->pwm_channels_mask = GENMASK(soc_info->num_channels - 1, 2);
> +	/*
> +	 * Enable all TCU channels for PWM use by default except channels 
> 0/1,
> +	 * and channel 2 if target CPU is JZ4780 and SMP is selected.
> +	 */
> +	tcu->pwm_channels_mask = GENMASK(soc_info->num_channels - 1,
> +								NR_CPUS + 1);
>  	of_property_read_u32(np, "ingenic,pwm-channels-mask",
>  			     (u32 *)&tcu->pwm_channels_mask);
>
> -	/* Verify that we have at least two free channels */
> -	if (hweight8(tcu->pwm_channels_mask) > soc_info->num_channels - 2) {
> +	/* Verify that we have at least NR_CPUS + 1 free channels */
> +	if (hweight8(tcu->pwm_channels_mask) >
> +			soc_info->num_channels - NR_CPUS + 1) {

NR_CPUS can be up to 256. You want to use num_online_cpus() here, I 
believe.

>  		pr_crit("%s: Invalid PWM channel mask: 0x%02lx\n", __func__,
>  			tcu->pwm_channels_mask);
>  		ret = -EINVAL;
> @@ -266,13 +324,27 @@ static int __init ingenic_tcu_init(struct 
> device_node *np)
>  	}
>
>  	tcu->map = map;
> +	tcu->np = np;
>  	ingenic_tcu = tcu;
>
> -	tcu->timer_channel = find_first_zero_bit(&tcu->pwm_channels_mask,
> +	tcu->timer_local[cpu] = find_first_zero_bit(&tcu->pwm_channels_mask,
>  						 soc_info->num_channels);
> -	tcu->cs_channel = find_next_zero_bit(&tcu->pwm_channels_mask,
> -					     soc_info->num_channels,
> -					     tcu->timer_channel + 1);
> +
> +	if (NR_CPUS > 1) {
> +		for (cpu = 1; cpu < NR_CPUS; cpu++)
> +			tcu->timer_local[cpu] = find_next_zero_bit(
> +						&tcu->pwm_channels_mask,
> +						soc_info->num_channels,
> +						tcu->timer_local[cpu - 1] + 1);
> +
> +		tcu->cs_channel = find_next_zero_bit(&tcu->pwm_channels_mask,
> +					soc_info->num_channels,
> +					tcu->timer_local[cpu-1] + 1);
> +	} else {
> +		tcu->cs_channel = find_next_zero_bit(&tcu->pwm_channels_mask,
> +					soc_info->num_channels,
> +					tcu->timer_local[cpu] + 1);
> +	}

I believe you can factorize the code a bit here - don't check for 
NR_CPUS > 1, and have a for (cpu = 0; cpu < num_online_cpus(); cpu++) 
loop. You could use a temporary variable to store the 'next bit' value.

-Paul

>  	ret = ingenic_tcu_clocksource_init(np, tcu);
>  	if (ret) {
> @@ -280,9 +352,10 @@ static int __init ingenic_tcu_init(struct 
> device_node *np)
>  		goto err_free_ingenic_tcu;
>  	}
>
> -	ret = ingenic_tcu_timer_init(np, tcu);
> -	if (ret)
> -		goto err_tcu_clocksource_cleanup;
> +	/* Setup clock events on each CPU core */
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "Ingenic XBurst: 
> online",
> +				ingenic_tcu_setup_cevt, NULL);
> +	WARN_ON(ret < 0);
>
>  	/* Register the sched_clock at the end as there's no way to undo it 
> */
>  	rate = clk_get_rate(tcu->cs_clk);
> @@ -290,10 +363,6 @@ static int __init ingenic_tcu_init(struct 
> device_node *np)
>
>  	return 0;
>
> -err_tcu_clocksource_cleanup:
> -	clocksource_unregister(&tcu->cs);
> -	clk_disable_unprepare(tcu->cs_clk);
> -	clk_put(tcu->cs_clk);
>  err_free_ingenic_tcu:
>  	kfree(tcu);
>  	return ret;
> --
> 2.7.4