Re: [PATCH v12 4/5] clocksource/drivers: Add a goldfish-timer clocksource

[Daniel Lezcano]

Hi Laurent,

On 21/01/2022 21:07, Laurent Vivier wrote:
> Add a clocksource based on the goldfish-rtc device.

As a first submission, please provide a more detailed description of the
timer.

> Signed-off-by: Laurent Vivier <laurent@xxxxxxxxx>
> ---
>  drivers/clocksource/Kconfig          |   7 ++
>  drivers/clocksource/Makefile         |   1 +
>  drivers/clocksource/timer-goldfish.c | 163 +++++++++++++++++++++++++++
>  include/clocksource/timer-goldfish.h |  11 ++
>  4 files changed, 182 insertions(+)
>  create mode 100644 drivers/clocksource/timer-goldfish.c
>  create mode 100644 include/clocksource/timer-goldfish.h
> 
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index cfb8ea0df3b1..94f00374cebb 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -721,4 +721,11 @@ config MICROCHIP_PIT64B
>  	  modes and high resolution. It is used as a clocksource
>  	  and a clockevent.
>  
> +config GOLDFISH_TIMER
> +	bool "Clocksource using goldfish-rtc"
> +	depends on M68K || COMPILE_TEST
> +	depends on RTC_DRV_GOLDFISH
> +	help
> +	  Support for the timer/counter of goldfish-rtc
> +
>  endmenu
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index fa5f624eadb6..12f5d7e8cc2d 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -89,3 +89,4 @@ obj-$(CONFIG_GX6605S_TIMER)		+= timer-gx6605s.o
>  obj-$(CONFIG_HYPERV_TIMER)		+= hyperv_timer.o
>  obj-$(CONFIG_MICROCHIP_PIT64B)		+= timer-microchip-pit64b.o
>  obj-$(CONFIG_MSC313E_TIMER)		+= timer-msc313e.o
> +obj-$(CONFIG_GOLDFISH_TIMER)		+= timer-goldfish.o
> diff --git a/drivers/clocksource/timer-goldfish.c b/drivers/clocksource/timer-goldfish.c
> new file mode 100644
> index 000000000000..4c670a1aea16
> --- /dev/null
> +++ b/drivers/clocksource/timer-goldfish.c
> @@ -0,0 +1,163 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/interrupt.h>
> +#include <linux/ioport.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +#include <linux/goldfish.h>
> +#include <clocksource/timer-goldfish.h>
> +
> +#define TIMER_TIME_LOW		0x00	/* get low bits of current time  */
> +					/*   and update TIMER_TIME_HIGH  */
> +#define TIMER_TIME_HIGH		0x04	/* get high bits of time at last */
> +					/*   TIMER_TIME_LOW read         */
> +#define TIMER_ALARM_LOW		0x08	/* set low bits of alarm and     */
> +					/*   activate it                 */
> +#define TIMER_ALARM_HIGH	0x0c	/* set high bits of next alarm   */

Thanks for the comments giving the update details of the register.
However the format is not very easy to read. I suggest to add these
information in the log or above the macros being a bit more verbose

/*
 * bla bla
 */

> +#define TIMER_IRQ_ENABLED	0x10
> +#define TIMER_CLEAR_ALARM	0x14
> +#define TIMER_ALARM_STATUS	0x18
> +#define TIMER_CLEAR_INTERRUPT	0x1c
> +
> +struct goldfish_timer {
> +	struct clocksource cs;
> +	struct clock_event_device ced;
> +	struct resource res;
> +	void __iomem *base;
> +	int irq;

'res' and 'irq' can be local variable in the init function, they are not
used anywhere else

> +};
> +
> +static struct goldfish_timer *ced_to_gf(struct clock_event_device *ced)
> +{
> +	return container_of(ced, struct goldfish_timer, ced);
> +}
> +
> +static struct goldfish_timer *cs_to_gf(struct clocksource *cs)
> +{
> +	return container_of(cs, struct goldfish_timer, cs);
> +}
> +
> +static u64 goldfish_timer_read(struct clocksource *cs)
> +{
> +	struct goldfish_timer *timerdrv = cs_to_gf(cs);
> +	void __iomem *base = timerdrv->base;
> +	u32 time_low, time_high;
> +	u64 ticks;
> +
> +	/*
> +	 * time_low: get low bits of current time and update time_high
> +	 * time_high: get high bits of time at last time_low read
> +	 */
> +	time_low = gf_ioread32(base + TIMER_TIME_LOW);
> +	time_high = gf_ioread32(base + TIMER_TIME_HIGH);
> +
> +	ticks = ((u64)time_high << 32) | time_low;
> +
> +	return ticks;
> +}
> +
> +static int goldfish_timer_set_oneshot(struct clock_event_device *evt)
> +{
> +	struct goldfish_timer *timerdrv = ced_to_gf(evt);
> +	void __iomem *base = timerdrv->base;
> +
> +	gf_iowrite32(0, base + TIMER_ALARM_HIGH);
> +	gf_iowrite32(0, base + TIMER_ALARM_LOW);
> +	gf_iowrite32(1, base + TIMER_IRQ_ENABLED);
> +
> +	return 0;
> +}
> +
> +static int goldfish_timer_shutdown(struct clock_event_device *evt)
> +{
> +	struct goldfish_timer *timerdrv = ced_to_gf(evt);
> +	void __iomem *base = timerdrv->base;
> +
> +	gf_iowrite32(0, base + TIMER_IRQ_ENABLED);
> +
> +	return 0;
> +}
> +
> +static int goldfish_timer_next_event(unsigned long delta,
> +				     struct clock_event_device *evt)
> +{
> +	struct goldfish_timer *timerdrv = ced_to_gf(evt);
> +	void __iomem *base = timerdrv->base;
> +	u64 now;
> +
> +	now = goldfish_timer_read(&timerdrv->cs);
> +
> +	now += delta;
> +
> +	gf_iowrite32(upper_32_bits(now), base + TIMER_ALARM_HIGH);
> +	gf_iowrite32(lower_32_bits(now), base + TIMER_ALARM_LOW);
> +
> +	return 0;
> +}
> +
> +static irqreturn_t golfish_timer_tick(int irq, void *dev_id)

"timer_tick" will be confusing with "scheduler timer tick". Please
rename it to (eg. goldfish_timer_irq)

Note: the function name 'golfish' instead of 'goldfish'

> +{
> +	struct clock_event_device *evt = dev_id;
> +	struct goldfish_timer *timerdrv = ced_to_gf(evt);
> +	void __iomem *base = timerdrv->base;
> +
> +	gf_iowrite32(1, base + TIMER_CLEAR_INTERRUPT);
> +
> +	evt->event_handler(evt);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +void __init goldfish_timer_init(int irq, void __iomem *base)

Error handling please

int __init goldfish_timer_init(...)

> +{
> +	struct goldfish_timer *timerdrv;
> +	int ret;
> +
> +	timerdrv = kzalloc(sizeof(*timerdrv), GFP_KERNEL);
> +	if (!timerdrv)
> +		return;
> +
> +	timerdrv->base = base;
> +	timerdrv->irq = irq;

Not needed

> +	timerdrv->ced = (struct clock_event_device){
> +		.name			= "goldfish_timer",
> +		.features		= CLOCK_EVT_FEAT_ONESHOT,
> +		.set_state_shutdown	= goldfish_timer_shutdown,
> +		.set_state_oneshot      = goldfish_timer_set_oneshot,
> +		.set_next_event		= goldfish_timer_next_event,
> +	};

nit: add CR

> +	timerdrv->res = (struct resource){
> +		.name  = "goldfish_timer",
> +		.start = (unsigned long)base,
> +		.end   = (unsigned long)base + 0xfff,
> +	};

Could be a local variable, no?

> +	if (request_resource(&iomem_resource, &timerdrv->res)) {
> +		pr_err("Cannot allocate goldfish-timer resource\n");

nit: pr_err("Cannot allocate '%s' resource\n", res.name);

> +		return;
> +	}
> +
> +	timerdrv->cs = (struct clocksource){
> +		.name		= "goldfish_timer",
> +		.rating		= 400,
> +		.read		= goldfish_timer_read,
> +		.mask		= CLOCKSOURCE_MASK(64),
> +		.flags		= 0,
> +		.max_idle_ns	= LONG_MAX,
> +	};
> +
> +	clocksource_register_hz(&timerdrv->cs, NSEC_PER_SEC);
> +
> +	ret = request_irq(timerdrv->irq, golfish_timer_tick, IRQF_TIMER,
> +			  "goldfish_timer", &timerdrv->ced);

Why not pass directly 'timerdrv' ?

> +	if (ret) {
> +		pr_err("Couldn't register goldfish-timer interrupt\n");
> +		return;
> +	}
> +
> +	clockevents_config_and_register(&timerdrv->ced, NSEC_PER_SEC,
> +					1, 0xffffffff);
> +}
> diff --git a/include/clocksource/timer-goldfish.h b/include/clocksource/timer-goldfish.h
> new file mode 100644
> index 000000000000..b237267844f1
> --- /dev/null
> +++ b/include/clocksource/timer-goldfish.h
> @@ -0,0 +1,11 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * goldfish-timer clocksource
> + */
> +
> +#ifndef _CLOCKSOURCE_GOLDFISH_TIMER_H
> +#define _CLOCKSOURCE_GOLDFISH_TIMER_H
> +
> +extern void goldfish_timer_init(int irq, void __iomem *base);
> +
> +#endif /* _CLOCKSOURCE_GOLDFISH_TIMER_H */
> 


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