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SubjectRe: [PATCH v2 2/2] driver: clocksource: Add nxp system counter timer driver support
From
Date
On 12/12/2018 06:28, Jacky Bai wrote:
> The system counter (sys_ctr) is a programmable system counter
> which provides a shared time base to the Cortex A15, A7, A53 etc cores.
> It is intended for use in applications where the counter is always
> powered on and supports multiple, unrelated clocks. The sys_ctr hardware
> supports:
> - 56-bit counter width (roll-over time greater than 40 years)
> - compare frame(64-bit compare value) contains programmable interrupt
> generation
>
> Signed-off-by: Bai Ping <ping.bai@nxp.com>
> ---
> change v1->v2:
> - no change
> ---
> drivers/clocksource/Kconfig | 8 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-imx-sysctr.c | 204 +++++++++++++++++++++++++++++++++
> 3 files changed, 213 insertions(+)
> create mode 100644 drivers/clocksource/timer-imx-sysctr.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index c57b156..7e5f2de 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -579,6 +579,14 @@ config CLKSRC_IMX_TPM
> Enable this option to use IMX Timer/PWM Module (TPM) timer as
> clocksource.
>
> +config CLKSRC_IMX_SYS_CTR

As the driver is a timer, please replace the CLKSRC by TIMER

> + bool "Clocksource using i.MX system counter" if COMPILE_TEST
> + depends on (ARM || ARM64) && CLKDEV_LOOKUP

CLKDEV_LOOKUP is not needed, it is selected with COMMON_CLK

> + select CLKSRC_MMIO
> + help
> + Enable this option to use IMX system counter timer as
> + clocksource.
> +
> config CLKSRC_ST_LPC
> bool "Low power clocksource found in the LPC" if COMPILE_TEST
> select TIMER_OF if OF
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index dd91381..372bf4e 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -71,6 +71,7 @@ obj-$(CONFIG_CLKSRC_MIPS_GIC) += mips-gic-timer.o
> obj-$(CONFIG_CLKSRC_TANGO_XTAL) += tango_xtal.o
> obj-$(CONFIG_CLKSRC_IMX_GPT) += timer-imx-gpt.o
> obj-$(CONFIG_CLKSRC_IMX_TPM) += timer-imx-tpm.o
> +obj-$(CONFIG_CLKSRC_IMX_SYS_CTR) += timer-imx-sysctr.o
> obj-$(CONFIG_ASM9260_TIMER) += asm9260_timer.o
> obj-$(CONFIG_H8300_TMR8) += h8300_timer8.o
> obj-$(CONFIG_H8300_TMR16) += h8300_timer16.o
> diff --git a/drivers/clocksource/timer-imx-sysctr.c b/drivers/clocksource/timer-imx-sysctr.c
> new file mode 100644
> index 0000000..ad3c27f
> --- /dev/null
> +++ b/drivers/clocksource/timer-imx-sysctr.c
> @@ -0,0 +1,204 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +//
> +// Copyright 2017-2018 NXP
> +
> +#include <linux/interrupt.h>
> +#include <linux/clockchips.h>
> +#include <linux/clocksource.h>
> +#include <linux/delay.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/sched_clock.h>
> +
> +#define CNTCV_LO 0x8
> +#define CNTCV_HI 0xc
> +#define CMPCV_LO 0x20
> +#define CMPCV_HI 0x24
> +#define CMPCR 0x2c
> +
> +#define SYS_CTR_EN 0x1
> +#define SYS_CTR_IRQ_MASK 0x2
> +
> +static void __iomem *sys_ctr_rd_base;
> +static void __iomem *sys_ctr_cmp_base;
> +static struct clock_event_device clockevent_sysctr;
> +
> +static inline void sysctr_timer_enable(bool enable)

Remove 'inline' tag

> +{
> + u32 val;
> +
> + val = readl(sys_ctr_cmp_base + CMPCR);
> + val &= ~SYS_CTR_EN;
> + if (enable)
> + val |= SYS_CTR_EN;
> +
> + writel(val, sys_ctr_cmp_base + CMPCR);
> +}
> +
> +static void sysctr_irq_acknowledge(void)
> +{
> + u32 val;
> +
> + /* clear th enable bit(EN=0) to clear the ISTAT */

What is the ISTAT?

Thanks for adding comments, however the format is:

/*
*
*/

> + val = readl(sys_ctr_cmp_base + CMPCR);
> + val &= ~SYS_CTR_EN;
> + writel(val, sys_ctr_cmp_base + CMPCR);

This is duplicate with the sysctr_timer_enable() function, call it
instead of duplicating code.

> +}
> +
> +static inline u64 sysctr_read_counter(void)
> +{
> + u32 cnt_hi, tmp_hi, cnt_lo;
> +
> + do {
> + cnt_hi = readl_relaxed(sys_ctr_rd_base + CNTCV_HI);
> + cnt_lo = readl_relaxed(sys_ctr_rd_base + CNTCV_LO);
> + tmp_hi = readl_relaxed(sys_ctr_rd_base + CNTCV_HI);
> + } while (tmp_hi != cnt_hi);
> +
> + return ((u64) cnt_hi << 32) | cnt_lo;
> +}

It has been showed a 64bit counter usage adds a non negligible overhead,
especially on 32bits. Are you really sure you want this ?

> +static u64 notrace sysctr_read_sched_clock(void)
> +{
> + return sysctr_read_counter();
> +}
> +
> +static u64 sysctr_clocksource_read(struct clocksource *cs)
> +{
> + return sysctr_read_counter();
> +}
> +
> +static int __init sysctr_clocksource_init(unsigned int rate)
> +{
> + sched_clock_register(sysctr_read_sched_clock, 56, rate);
> + return clocksource_mmio_init(sys_ctr_rd_base, "i.MX sys_ctr",
> + rate, 200, 56, sysctr_clocksource_read);
> +}
> +
> +static int sysctr_set_next_event(unsigned long delta,
> + struct clock_event_device *evt)
> +{
> + u32 cmp_hi, cmp_lo;
> + u64 next;
> +
> + sysctr_timer_enable(false);
> +
> + next = sysctr_read_counter();
> +
> + next += delta;
> +
> + cmp_hi = (next >> 32) & 0x00fffff;
> + cmp_lo = next & 0xffffffff;
> +
> + writel_relaxed(cmp_hi, sys_ctr_cmp_base + CMPCV_HI);
> + writel_relaxed(cmp_lo, sys_ctr_cmp_base + CMPCV_LO);
> +
> + sysctr_timer_enable(true);
> +
> + return 0;
> +}
> +
> +static int sysctr_set_state_oneshot(struct clock_event_device *evt)
> +{
> + /* enable timer */

The function name is explicit enough, no need to add this comment

> + sysctr_timer_enable(true);
> +
> + return 0;
> +}
> +
> +static int sysctr_set_state_shutdown(struct clock_event_device *evt)
> +{
> + /* disable the timer */

Ditto

> + sysctr_timer_enable(false);
> +
> + return 0;
> +}
> +
> +static irqreturn_t sysctr_timer_interrupt(int irq, void *dev_id)
> +{
> + struct clock_event_device *evt = &clockevent_sysctr;
> +
> + sysctr_irq_acknowledge();
> +
> + evt->event_handler(evt);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static struct clock_event_device clockevent_sysctr = {
> + .name = "i.MX system counter timer",
> + .features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ,
> + .set_state_oneshot = sysctr_set_state_oneshot,
> + .set_next_event = sysctr_set_next_event,
> + .set_state_shutdown = sysctr_set_state_shutdown,
> + .rating = 200,
> +};
> +
> +static int __init sysctr_clockevent_init(unsigned long rate, int irq)
> +{
> + int ret;
> +
> + ret = request_irq(irq, sysctr_timer_interrupt, IRQF_TIMER | IRQF_IRQPOLL,
> + "i.MX system counter timer", &clockevent_sysctr);
> + if (ret) {
> + pr_err("Failed to request i.MX sysctr timer irq\n");
> + return ret;
> + }
> +
> + clockevent_sysctr.cpumask = cpumask_of(0);
> + clockevent_sysctr.irq = irq;
> + clockevents_config_and_register(&clockevent_sysctr,
> + rate, 0xff, 0x7fffffff);
> + return 0;
> +}
> +
> +static int __init sysctr_timer_init(struct device_node *np)
> +{
> + u32 rate;
> + int irq, ret = 0;
> +
> + /* map the system counter's CNTreadbase */

Comment not useful, remove it

> + sys_ctr_rd_base = of_iomap(np, 0);
> + if (!sys_ctr_rd_base) {
> + pr_err("Failed to map sys_ctr rd base%pOF\n", np);

nit: space missing after 'base'

> + return -ENXIO;
> + }
> +
> + /* map the system counter's CNTcomparebase */

Remove comment

> + sys_ctr_cmp_base = of_iomap(np, 1);
> + if (!sys_ctr_cmp_base) {
> + pr_err("Failed to map sys_ctr compare base%pOF\n", np);
> + ret = -ENXIO;
> + goto out_free2;
> + }
> +
> + /*
> + * the purpose of this driver is to provide a global timer,
> + * So only use one compare frame, request frame0's irq only.
> + */
> + irq = irq_of_parse_and_map(np, 0);
> + if (!irq) {
> + pr_err("Failed to map interrupt for %pOF\n", np);
> + ret = -EINVAL;
> + goto out_free1;
> + }
> +
> + if (of_property_read_u32(np, "clock-frequency", &rate)) {
> + pr_err("Failed to get clock frequency %pOF\n", np);
> + ret = -EINVAL;
> + goto out_free1;
> + }

Please replace it with a 'fixed-clock' in the DT and use the clk API.

In addition you can use the timer-of API (cf timer-of.h)

> +
> + sysctr_clocksource_init(rate);
> + sysctr_clockevent_init(rate, irq);
> +
> + return 0;
> +
> +out_free1:

label names are inadequate, use out_iounmap_cmp: for example

> + iounmap(sys_ctr_cmp_base);
> +out_free2:
> + iounmap(sys_ctr_rd_base);
> + return ret;
> +}
> +TIMER_OF_DECLARE(sysctr_timer, "nxp,sysctr-timer", sysctr_timer_init);
>


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