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SubjectRe: [PATCH v4 2/2] driver: clocksource: Add nxp system counter timer driver support
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On 21/05/2019 09:18, Jacky Bai wrote:
> From: Bai Ping <ping.bai@nxp.com>
>
> 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)

The benefit of using more than 32bits on a 32bits system is not proven.

The function to read and build the 56bits value can have a very
significant impact on the performance of your platform.

Using a 32bits counter can be enough if it does not wrap too fast.

Can you consider a 32 bits counter ?

> - compare frame(64-bit compare value) contains programmable interrupt
> generation when compare value <= counter value.
>
> Signed-off-by: Bai Ping <ping.bai@nxp.com>
> ---
> change v1->v2:
> - no change
> change v2->v3:
> - remove the clocksource, we only need to use this module for timer purpose,
> so register it as clockevent is enough.
> - use the timer_of_init to init the irq, clock, etc.
> - remove some unnecessary comments.
> change v3->v4:
> - use cached value for CMPCR,
> - remove unnecessary timer enabe from set_state_oneshot function.
> ---
> drivers/clocksource/Kconfig | 7 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-imx-sysctr.c | 146 +++++++++++++++++++++++++
> 3 files changed, 154 insertions(+)
> create mode 100644 drivers/clocksource/timer-imx-sysctr.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 6bcaa4e2e72c..ee48620a4561 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -616,6 +616,13 @@ config CLKSRC_IMX_TPM
> Enable this option to use IMX Timer/PWM Module (TPM) timer as
> clocksource.
>
> +config TIMER_IMX_SYS_CTR
> + bool "i.MX system counter timer" if COMPILE_TEST
> + depends on ARCH_MXC

Do you really need this dep?

> + select TIMER_OF
> + help
> + Enable this option to use i.MX system counter timer for clockevent.
> +
> 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 236858fa7fbf..5fba39e81a40 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -74,6 +74,7 @@ obj-$(CONFIG_CLKSRC_MIPS_GIC) += mips-gic-timer.o
> obj-$(CONFIG_CLKSRC_TANGO_XTAL) += timer-tango-xtal.o
> obj-$(CONFIG_CLKSRC_IMX_GPT) += timer-imx-gpt.o
> obj-$(CONFIG_CLKSRC_IMX_TPM) += timer-imx-tpm.o
> +obj-$(CONFIG_TIMER_IMX_SYS_CTR) += timer-imx-sysctr.o
> obj-$(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 000000000000..d0428d3189f8
> --- /dev/null
> +++ b/drivers/clocksource/timer-imx-sysctr.c
> @@ -0,0 +1,146 @@
> +// SPDX-License-Identifier: GPL-2.0+
> +//
> +// Copyright 2017-2019 NXP
> +
> +#include <linux/interrupt.h>
> +#include <linux/clockchips.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +
> +#include "timer-of.h"
> +
> +#define CMP_OFFSET 0x10000
> +
> +#define CNTCV_LO 0x8
> +#define CNTCV_HI 0xc
> +#define CMPCV_LO (CMP_OFFSET + 0x20)
> +#define CMPCV_HI (CMP_OFFSET + 0x24)
> +#define CMPCR (CMP_OFFSET + 0x2c)
> +
> +#define SYS_CTR_EN 0x1
> +#define SYS_CTR_IRQ_MASK 0x2
> +
> +static void __iomem *sys_ctr_base;
> +static u32 cmpcr;
> +
> +static void sysctr_timer_enable(bool enable)
> +{
> + cmpcr &= ~SYS_CTR_EN;

Do the computation after reading the value in the init function...

> + if (enable)
> + cmpcr |= SYS_CTR_EN;

... then

writel(enable ? cmpcr | SYS_CTR_EN : cmpcr, sys_ctr_base);

> + writel(cmpcr, sys_ctr_base + CMPCR);
> +}
> +
> +static void sysctr_irq_acknowledge(void)
> +{
> + /*
> + * clear the enable bit(EN =0) will clear
> + * the status bit(ISTAT = 0), then the interrupt
> + * signal will be negated(acknowledged).
> + */
> + sysctr_timer_enable(false);
> +}
> +
> +static inline u64 sysctr_read_counter(void)
> +{
> + u32 cnt_hi, tmp_hi, cnt_lo;
> +
> + do {
> + cnt_hi = readl_relaxed(sys_ctr_base + CNTCV_HI);
> + cnt_lo = readl_relaxed(sys_ctr_base + CNTCV_LO);
> + tmp_hi = readl_relaxed(sys_ctr_base + CNTCV_HI);
> + } while (tmp_hi != cnt_hi);
> +
> + return ((u64) cnt_hi << 32) | cnt_lo;
> +}
> +
> +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_base + CMPCV_HI);
> + writel_relaxed(cmp_lo, sys_ctr_base + CMPCV_LO);
> +
> + sysctr_timer_enable(true);
> +
> + return 0;
> +}
> +
> +static int sysctr_set_state_oneshot(struct clock_event_device *evt)
> +{
> + return 0;
> +}
> +
> +static int sysctr_set_state_shutdown(struct clock_event_device *evt)
> +{
> + sysctr_timer_enable(false);
> +
> + return 0;
> +}
> +
> +static irqreturn_t sysctr_timer_interrupt(int irq, void *dev_id)
> +{
> + struct clock_event_device *evt = dev_id;
> +
> + sysctr_irq_acknowledge();
> +
> + evt->event_handler(evt);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static struct timer_of to_sysctr = {
> + .flags = TIMER_OF_IRQ | TIMER_OF_CLOCK | TIMER_OF_BASE,
> + .clkevt = {
> + .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,
> + },
> + .of_irq = {
> + .handler = sysctr_timer_interrupt,
> + .flags = IRQF_TIMER | IRQF_IRQPOLL,
> + },
> + .of_clk = {
> + .name = "per",
> + },
> +};
> +
> +static void __init sysctr_clockevent_init(void)
> +{
> + to_sysctr.clkevt.cpumask = cpumask_of(0);
> +
> + clockevents_config_and_register(&to_sysctr.clkevt, timer_of_rate(&to_sysctr),
> + 0xff, 0x7fffffff);
> +}
> +
> +static int __init sysctr_timer_init(struct device_node *np)
> +{
> + int ret = 0;
> +
> + ret = timer_of_init(np, &to_sysctr);
> + if (ret)
> + return ret;
> +
> + sys_ctr_base = timer_of_base(&to_sysctr);
> + cmpcr = readl(sys_ctr_base + CMPCR);
> +
> + sysctr_clockevent_init();
> +
> + return 0;
> +}
> +TIMER_OF_DECLARE(sysctr_timer, "nxp,sysctr-timer", sysctr_timer_init);
>


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