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Date: Wed, 26 Jan 2022 12:55:05 +0100
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Laurent Vivier <laurent@...ier.eu>, linux-kernel@...r.kernel.org
Cc: linux-rtc@...r.kernel.org, Alessandro Zummo <a.zummo@...ertech.it>,
Jiaxun Yang <jiaxun.yang@...goat.com>,
Geert Uytterhoeven <geert@...ux-m68k.org>,
linux-m68k@...ts.linux-m68k.org, Arnd Bergmann <arnd@...db.de>,
Thomas Gleixner <tglx@...utronix.de>,
Stephen Boyd <sboyd@...nel.org>,
Alexandre Belloni <alexandre.belloni@...tlin.com>,
John Stultz <john.stultz@...aro.org>
Subject: Re: [PATCH v12 4/5] clocksource/drivers: Add a goldfish-timer
clocksource
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@...ier.eu>
> ---
> 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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