Re: [PATCH v12 4/5] clocksource/drivers: Add a goldfish-timer clocksource
From: Laurent Vivier
Date: Wed Jan 26 2022 - 12:14:56 EST
Le 26/01/2022 à 12:55, Daniel Lezcano a écrit :
Hi Laurent,
Hi Daniel,
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.
ok.
The timer uses in fact the goldifsh RTC clock so I supposed refering to drivers/rtc/rtc-goldfish.c
could give the missing pieces of information
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
*/
In fact, I copied them from drivers/rtc/rtc-goldfish.c but I can update this as you say.
+#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
I agree for irq, but res is passed to request_resource() and I think it is added to a linked tree,
so I'm not sure it can be local to the function.
Do you mean a "static" declaration in the function?
+};
+
+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'
ok
+{
+ 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(...)
ok
+{
+ struct goldfish_timer *timerdrv;
+ int ret;
+
+ timerdrv = kzalloc(sizeof(*timerdrv), GFP_KERNEL);
+ if (!timerdrv)
+ return;
+
+ timerdrv->base = base;
+ timerdrv->irq = irq;
Not needed
ok
+ 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
ok
+ timerdrv->res = (struct resource){
+ .name = "goldfish_timer",
+ .start = (unsigned long)base,
+ .end = (unsigned long)base + 0xfff,
+ };
Could be a local variable, no?
As I said above, I think the structure passed to request_resource() must not be released.
+ 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);
ok
+ 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' ?
You're right, we can pass it directly.
+ 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 */