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Message-ID: <27e8d6f0-b415-f31e-ae89-0b35397d0cf2@linaro.org>
Date: Tue, 10 Jul 2018 18:20:13 +0200
From: Daniel Lezcano <daniel.lezcano@...aro.org>
To: Clément Péron <peron.clem@...il.com>,
Colin Didier <colin.didier@...ialet.com>,
linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Cc: Stefan Agner <stefan@...er.ch>,
Thomas Gleixner <tglx@...utronix.de>,
Fabio Estevam <fabio.estevam@....com>,
Vladimir Zapolskiy <vladimir_zapolskiy@...tor.com>,
Sascha Hauer <s.hauer@...gutronix.de>,
Rob Herring <robh@...nel.org>,
NXP Linux Team <linux-imx@....com>,
Pengutronix Kernel Team <kernel@...gutronix.de>,
Clément Peron <clement.peron@...ialet.com>
Subject: Re: [PATCH v7 4/5] clocksource: add driver for i.MX EPIT timer
On 11/06/2018 17:50, Clément Péron wrote:
> From: Colin Didier <colin.didier@...ialet.com>
>
> Add driver for NXP's EPIT timer used in i.MX SoC.
Give a description on how works this timer.
> Signed-off-by: Colin Didier <colin.didier@...ialet.com>
> Signed-off-by: Clément Peron <clement.peron@...ialet.com>
> Reviewed-by: Vladimir Zapolskiy <vz@...ia.com>
> Tested-by: Vladimir Zapolskiy <vz@...ia.com>
> ---
> drivers/clocksource/Kconfig | 11 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-imx-epit.c | 265 +++++++++++++++++++++++++++
> 3 files changed, 277 insertions(+)
> create mode 100644 drivers/clocksource/timer-imx-epit.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 8e8a09755d10..790478afd02c 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -576,6 +576,17 @@ config H8300_TPU
> This enables the clocksource for the H8300 platform with the
> H8S2678 cpu.
>
> +config CLKSRC_IMX_EPIT
> + bool "Clocksource using i.MX EPIT"
> + depends on CLKDEV_LOOKUP && (ARCH_MXC || COMPILE_TEST)
> + select CLKSRC_MMIO
> + help
> + This enables EPIT support available on some i.MX platforms.
> + Normally you don't have a reason to do so as the EPIT has
> + the same features and uses the same clocks as the GPT.
> + Anyway, on some systems the GPT may be in use for other
> + purposes.
> +
> config CLKSRC_IMX_GPT
> bool "Clocksource using i.MX GPT" if COMPILE_TEST
> depends on ARM && CLKDEV_LOOKUP
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 00caf37e52f9..d9426f69ec69 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -69,6 +69,7 @@ obj-$(CONFIG_INTEGRATOR_AP_TIMER) += timer-integrator-ap.o
> obj-$(CONFIG_CLKSRC_VERSATILE) += versatile.o
> obj-$(CONFIG_CLKSRC_MIPS_GIC) += mips-gic-timer.o
> obj-$(CONFIG_CLKSRC_TANGO_XTAL) += tango_xtal.o
> +obj-$(CONFIG_CLKSRC_IMX_EPIT) += timer-imx-epit.o
> obj-$(CONFIG_CLKSRC_IMX_GPT) += timer-imx-gpt.o
> obj-$(CONFIG_CLKSRC_IMX_TPM) += timer-imx-tpm.o
> obj-$(CONFIG_ASM9260_TIMER) += asm9260_timer.o
> diff --git a/drivers/clocksource/timer-imx-epit.c b/drivers/clocksource/timer-imx-epit.c
> new file mode 100644
> index 000000000000..7f1c8e2e00aa
> --- /dev/null
> +++ b/drivers/clocksource/timer-imx-epit.c
> @@ -0,0 +1,265 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * i.MX EPIT Timer
> + *
> + * Copyright (C) 2010 Sascha Hauer <s.hauer@...gutronix.de>
> + * Copyright (C) 2018 Colin Didier <colin.didier@...ialet.com>
> + * Copyright (C) 2018 Clément Péron <clement.peron@...ialet.com>
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clockchips.h>
> +#include <linux/interrupt.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/sched_clock.h>
> +#include <linux/slab.h>
> +
> +#define EPITCR 0x00
> +#define EPITSR 0x04
> +#define EPITLR 0x08
> +#define EPITCMPR 0x0c
> +#define EPITCNR 0x10
> +
> +#define EPITCR_EN BIT(0)
> +#define EPITCR_ENMOD BIT(1)
> +#define EPITCR_OCIEN BIT(2)
> +#define EPITCR_RLD BIT(3)
> +#define EPITCR_PRESC(x) (((x) & 0xfff) << 4)
> +#define EPITCR_SWR BIT(16)
> +#define EPITCR_IOVW BIT(17)
> +#define EPITCR_DBGEN BIT(18)
> +#define EPITCR_WAITEN BIT(19)
> +#define EPITCR_RES BIT(20)
> +#define EPITCR_STOPEN BIT(21)
> +#define EPITCR_OM_DISCON (0 << 22)
> +#define EPITCR_OM_TOGGLE (1 << 22)
> +#define EPITCR_OM_CLEAR (2 << 22)
> +#define EPITCR_OM_SET (3 << 22)
> +#define EPITCR_CLKSRC_OFF (0 << 24)
> +#define EPITCR_CLKSRC_PERIPHERAL (1 << 24)
> +#define EPITCR_CLKSRC_REF_HIGH (2 << 24)
> +#define EPITCR_CLKSRC_REF_LOW (3 << 24)
> +
> +#define EPITSR_OCIF BIT(0)
> +
> +struct epit_timer {
> + void __iomem *base;
> + int irq;
> + struct clk *clk;
> + struct clock_event_device ced;
> + struct irqaction act;
> +};
> +
> +static void __iomem *sched_clock_reg;
> +
> +static inline struct epit_timer *to_epit_timer(struct clock_event_device *ced)
> +{
> + return container_of(ced, struct epit_timer, ced);
> +}
> +
> +static inline void epit_irq_disable(struct epit_timer *epittm)
> +{
> + u32 val;
> +
> + val = readl_relaxed(epittm->base + EPITCR);
> + writel_relaxed(val & ~EPITCR_OCIEN, epittm->base + EPITCR);
> +}
> +
> +static inline void epit_irq_enable(struct epit_timer *epittm)
> +{
> + u32 val;
> +
> + val = readl_relaxed(epittm->base + EPITCR);
> + writel_relaxed(val | EPITCR_OCIEN, epittm->base + EPITCR);
> +}
> +
> +static void epit_irq_acknowledge(struct epit_timer *epittm)
> +{
> + writel_relaxed(EPITSR_OCIF, epittm->base + EPITSR);
> +}
> +
> +static u64 notrace epit_read_sched_clock(void)
> +{
> + return ~readl_relaxed(sched_clock_reg);
> +}
> +
> +static int epit_set_next_event(unsigned long cycles,
> + struct clock_event_device *ced)
> +{
> + struct epit_timer *epittm = to_epit_timer(ced);
> + unsigned long tcmp;
> +
> + tcmp = readl_relaxed(epittm->base + EPITCNR) - cycles;
> + writel_relaxed(tcmp, epittm->base + EPITCMPR);
> +
> + return 0;
> +}
> +
> +/* Left event sources disabled, no more interrupts appear */
> +static int epit_shutdown(struct clock_event_device *ced)
> +{
> + struct epit_timer *epittm = to_epit_timer(ced);
> + unsigned long flags;
> +
> + /*
> + * The timer interrupt generation is disabled at least
> + * for enough time to call epit_set_next_event()
> + */
> + local_irq_save(flags);
This is not necessary. This function is called with interrupt disabled.
> + /* Disable interrupt in EPIT module */
> + epit_irq_disable(epittm);
> +
> + /* Clear pending interrupt */
> + epit_irq_acknowledge(epittm);
No irq ack is needed here. Neither disabling the interrupt.
Why not just stop the counter ?
> + local_irq_restore(flags);
> +
> + return 0;
> +}
> +
> +static int epit_set_oneshot(struct clock_event_device *ced)
> +{
> + struct epit_timer *epittm = to_epit_timer(ced);
> + unsigned long flags;
> +
> + /*
> + * The timer interrupt generation is disabled at least
> + * for enough time to call epit_set_next_event()
> + */
> + local_irq_save(flags);
This is not necessary. This function is called with interrupt disabled.
> + /* Disable interrupt in EPIT module */
> + epit_irq_disable(epittm);
> +
> + /* Clear pending interrupt, only while switching mode */
> + if (!clockevent_state_oneshot(ced))
> + epit_irq_acknowledge(epittm);
Why do you need to ack the interrupt here ?
> + /*
> + * Do not put overhead of interrupt enable/disable into
> + * epit_set_next_event(), the core has about 4 minutes
> + * to call epit_set_next_event() or shutdown clock after
> + * mode switching
> + */
> + epit_irq_enable(epittm);
> + local_irq_restore(flags);
> +
> + return 0;
> +}
> +
> +static irqreturn_t epit_timer_interrupt(int irq, void *dev_id)
> +{
> + struct clock_event_device *ced = dev_id;
> + struct epit_timer *epittm = to_epit_timer(ced);
> +
> + epit_irq_acknowledge(epittm);
> +
> + ced->event_handler(ced);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int __init epit_clocksource_init(struct epit_timer *epittm)
> +{
> + unsigned int c = clk_get_rate(epittm->clk);
> +
> + sched_clock_reg = epittm->base + EPITCNR;
> + sched_clock_register(epit_read_sched_clock, 32, c);
> +
> + return clocksource_mmio_init(epittm->base + EPITCNR, "epit", c, 200, 32,
> + clocksource_mmio_readl_down);
> +}
> +
> +static int __init epit_clockevent_init(struct epit_timer *epittm)
> +{
> + struct clock_event_device *ced = &epittm->ced;
> + struct irqaction *act = &epittm->act;
> +
> + ced->name = "epit";
> + ced->features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_DYNIRQ;
> + ced->set_state_shutdown = epit_shutdown;
> + ced->tick_resume = epit_shutdown;
> + ced->set_state_oneshot = epit_set_oneshot;
> + ced->set_next_event = epit_set_next_event;
> + ced->rating = 200;
> + ced->cpumask = cpumask_of(0);
> + ced->irq = epittm->irq;
> + clockevents_config_and_register(ced, clk_get_rate(epittm->clk),
> + 0xff, 0xfffffffe);
> +
> + act->name = "i.MX EPIT Timer Tick",
> + act->flags = IRQF_TIMER | IRQF_IRQPOLL;
> + act->handler = epit_timer_interrupt;
> + act->dev_id = ced;
> +
> + /* Make irqs happen */
> + return setup_irq(epittm->irq, act);
> +}
> +
> +static int __init epit_timer_init(struct device_node *np)
> +{
> + struct epit_timer *epittm;
> + int ret;
> +
> + epittm = kzalloc(sizeof(*epittm), GFP_KERNEL);
> + if (!epittm)
> + return -ENOMEM;
> +
> + epittm->base = of_iomap(np, 0);
> + if (!epittm->base) {
> + ret = -ENXIO;
> + goto out_kfree;
> + }
> +
> + epittm->irq = irq_of_parse_and_map(np, 0);
> + if (!epittm->irq) {
> + ret = -EINVAL;
> + goto out_iounmap;
> + }
> +
> + /* Get EPIT clock */
> + epittm->clk = of_clk_get(np, 0);
> + if (IS_ERR(epittm->clk)) {
> + pr_err("i.MX EPIT: unable to get clk\n");
> + ret = PTR_ERR(epittm->clk);
> + goto out_iounmap;
> + }
> +
> + ret = clk_prepare_enable(epittm->clk);
> + if (ret) {
> + pr_err("i.MX EPIT: unable to prepare+enable clk\n");
> + goto out_iounmap;
> + }
Please replace all the above with the timer-of API as:
https://patchwork.kernel.org/patch/10510443/
> + /* Initialise to a known state (all timers off, and timing reset) */
> + writel_relaxed(0x0, epittm->base + EPITCR);
> + writel_relaxed(0xffffffff, epittm->base + EPITLR);
> + writel_relaxed(EPITCR_EN | EPITCR_CLKSRC_REF_HIGH | EPITCR_WAITEN,
> + epittm->base + EPITCR);
> +
> + ret = epit_clocksource_init(epittm);
> + if (ret) {
> + pr_err("i.MX EPIT: failed to init clocksource\n");
> + goto out_clk_disable;
> + }
> +
> + ret = epit_clockevent_init(epittm);
> + if (ret) {
> + pr_err("i.MX EPIT: failed to init clockevent\n");
> + goto out_clk_disable;
> + }
> +
> + return 0;
> +
> +out_clk_disable:
> + clk_disable_unprepare(epittm->clk);
> +out_iounmap:
> + iounmap(epittm->base);
> +out_kfree:
> + kfree(epittm);
> +
> + return ret;
> +}
> +TIMER_OF_DECLARE(epit_timer, "fsl,imx31-epit", epit_timer_init);
>
--
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