Re: [PATCH v3 04/10] clocksource/drivers: Add HPE GXP timer

Daniel Lezcano
2022-04-06T14:43:19Z

On 10/03/2022 20:52, nick.hawkins@hpe.com wrote:
> From: Nick Hawkins <nick.hawkins@hpe.com>
>
> Add support for the HPE GXP SOC timer. The GXP supports several
> different kinds of timers but for the purpose of this driver there
> is only support for the General Timer. The timer has a 1us
> resolution and is 32 bits.
>
> Signed-off-by: Nick Hawkins <nick.hawkins@hpe.com>
> ---
> drivers/clocksource/Kconfig | 8 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/gxp-timer.c | 159 ++++++++++++++++++++++++++++++++
> 3 files changed, 168 insertions(+)
> create mode 100644 drivers/clocksource/gxp-timer.c

Please for the sake of consistency, rename the timer to timer-qxp.c

> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index cfb8ea0df3b1..5916dade7608 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -617,6 +617,14 @@ config CLKSRC_ST_LPC
> Enable this option to use the Low Power controller timer
> as clocksource.
>
> +config GXP_TIMER
> + bool "GXP timer driver"
> + depends on ARCH_HPE
> + default y
> + help
> + Provides a driver for the timer control found on HPE
> + GXP SOCs. This is required for all GXP SOCs.

Regarding the silent option:

https://www.spinics.net/lists/arm-kernel/msg936976.html

> config ATCPIT100_TIMER
> bool "ATCPIT100 timer driver"
> depends on NDS32 || COMPILE_TEST
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index fa5f624eadb6..dbfb8c56a8a0 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_GXP_TIMER) += gxp-timer.o
> diff --git a/drivers/clocksource/gxp-timer.c b/drivers/clocksource/gxp-timer.c
> new file mode 100644
> index 000000000000..a24cd1cc5c04
> --- /dev/null
> +++ b/drivers/clocksource/gxp-timer.c
> @@ -0,0 +1,159 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (C) 2022 Hewlett-Packard Enterprise Development Company, L.P.*/
> +
> +#include <linux/bitops.h>
> +#include <linux/clockchips.h>
> +#include <linux/clocksource.h>
> +#include <linux/interrupt.h>
> +#include <linux/irqreturn.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
This header is not needed.

> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/of_platform.h>
> +#include <linux/slab.h>
> +#include <linux/string.h>
> +#include <linux/sched_clock.h>
> +
> +#include <asm/irq.h>

This header is not needed AFAICT.

Please double check the headers above are all needed.

> +#define TIMER0_FREQ 1000000
> +
> +/*TCS Stands for Timer Control/Status: these are masks to be used in*/
> +/* the Timer Count Registers */
> +#define MASK_TCS_ENABLE 0x01
> +#define MASK_TCS_PERIOD 0x02
> +#define MASK_TCS_RELOAD 0x04
> +#define MASK_TCS_TC 0x80
> +
> +struct gxp_timer {
> + void __iomem *counter;
> + void __iomem *control;
> + struct clock_event_device evt;
> +};
> +
> +static void __iomem *system_clock __read_mostly;
> +
> +static inline struct gxp_timer *to_gxp_timer(struct clock_event_device *evt_dev)
> +{
> + return container_of(evt_dev, struct gxp_timer, evt);
> +}
> +
> +static u64 notrace gxp_sched_read(void)
> +{
> + return readl_relaxed(system_clock);
> +}
> +
> +static int gxp_time_set_next_event(unsigned long event,
> + struct clock_event_device *evt_dev)
> +{
> + struct gxp_timer *timer = to_gxp_timer(evt_dev);

nit: add a line to separate the declaration and the code below.

> + /* Stop counting and disable interrupt before updating */
> + writeb_relaxed(MASK_TCS_TC, timer->control);
> + writel_relaxed(event, timer->counter);
> + writeb_relaxed(MASK_TCS_TC | MASK_TCS_ENABLE, timer->control);
> +
> + return 0;
> +}
> +
> +static irqreturn_t gxp_time_interrupt(int irq, void *dev_id)

s/gxp_time/gxp_timer/

> +{
> + struct gxp_timer *timer = dev_id;
> + void (*event_handler)(struct clock_event_device *timer);
> +
> + if (!(readb_relaxed(timer->control) & MASK_TCS_TC))
> + return IRQ_NONE;
> +
> + writeb_relaxed(MASK_TCS_TC, timer->control);
> +
> + event_handler = READ_ONCE(timer->evt.event_handler);
> + event_handler(&timer->evt);

Why READ_ONCE ?

Do timer->evt.event_handler();

Or alternatively pass the request_irq() &timer->evt and use to_gxp_timer()

> + return IRQ_HANDLED;
> +}
> +
> +static int __init gxp_timer_init(struct device_node *node)
> +{
> + void __iomem *base_counter;
> + void __iomem *base_control;
> + u32 freq;
> + int ret, irq;
> + struct gxp_timer *gxp_timer;
> +
> + base_counter = of_iomap(node, 0);
> + if (!base_counter) {
> + pr_err("Can't remap counter registers");
> + ret = -ENXIO;
> + return ret;

return -ENXIO;

> + }
> +
> + base_control = of_iomap(node, 1);
> + if (!base_control) {
> + pr_err("Can't remap control registers");
> + ret = -ENXIO;
> + goto err_iounmap;

> + }
> +
> + system_clock = of_iomap(node, 2);
> + if (!system_clock) {
> + pr_err("Can't remap control registers");
> + ret = -ENXIO;
> + goto err_iounmap;
> + }
> +
> + if (of_property_read_u32(node, "clock-frequency", &freq)) {
> + pr_err("Can't read clock-frequency\n");
> + ret = -EIO;
> + goto err_iounmap;
> + }
> +
> + sched_clock_register(gxp_sched_read, 32, freq);
> + clocksource_mmio_init(system_clock, node->name, freq,
> + 300, 32, clocksource_mmio_readl_up);
> +
> + irq = irq_of_parse_and_map(node, 0);
> + if (irq <= 0) {
> + ret = -EINVAL;
> + pr_err("GXP Timer Can't parse IRQ %d", irq);
> + goto err_iounmap;
> + }
> +
> + gxp_timer = kzalloc(sizeof(*gxp_timer), GFP_KERNEL);
> + if (!gxp_timer) {
> + ret = -ENOMEM;
> + goto err_iounmap;
> + }
> +
> + gxp_timer->counter = base_counter;
> + gxp_timer->control = base_control;
> + gxp_timer->evt.name = node->name; > + gxp_timer->evt.rating = 300;
> + gxp_timer->evt.features = CLOCK_EVT_FEAT_ONESHOT;
> + gxp_timer->evt.set_next_event = gxp_time_set_next_event;
> + gxp_timer->evt.cpumask = cpumask_of(0);
> +

ret = request_irq();

> + if (request_irq(irq, gxp_time_interrupt, IRQF_TIMER | IRQF_SHARED,
> + node->name, gxp_timer)) {
> + ret = -EIO;

Remove above ret = -EIO;

> + pr_err("%s: request_irq() failed\n", "GXP Timer Tick");
> + goto err_timer_free;
> + }
> +
> + clockevents_config_and_register(&gxp_timer->evt, TIMER0_FREQ,
> + 0xf, 0xffffffff);
> +
> + pr_info("gxp: system timer (irq = %d)\n", irq);

s/pr_info/pr_debug/

> + return 0;
> +
> +
> +err_timer_free:
> + kfree(gxp_timer);
> +
> +err_iounmap:
> + iounmap(system_clock);
> + iounmap(base_control);
> + iounmap(base_counter);
> + return ret;
> +}
> +
> +TIMER_OF_DECLARE(gxp, "hpe,gxp-timer", gxp_timer_init);

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