Re: [RFC PATCH 02/10] clockevents/drivers: add MPS2 Timer driver

Daniel Lezcano
2015-11-25T13:40:04Z

On 11/25/2015 11:33 AM, Vladimir Murzin wrote:
> MPS2 platform has simple 32 bits general purpose countdown timers.
>
> The driver uses the first detected timer as a clocksource and the rest
> of the timers as a clockevent
>
> Signed-off-by: Vladimir Murzin <vladimir.murzin-5wv7dgnIgG8@public.gmane.org>
> ---
> drivers/clocksource/Kconfig | 5 +
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/mps2-timer.c | 280 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 286 insertions(+)
> create mode 100644 drivers/clocksource/mps2-timer.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index 71cfdf7..552ab54 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -136,6 +136,11 @@ config CLKSRC_STM32
> depends on OF && ARM && (ARCH_STM32 || COMPILE_TEST)
> select CLKSRC_MMIO
>
> +config CLKSRC_MPS2
> + bool "Clocksource for MPS2 SoCs"
> + depends on OF && (ARM || COMPILE_TEST)

bool "Clocksource for MPS2 SoCs" if COMPILE_TEST
depends on OF && ARM

> + select CLKSRC_MMIO
> +
> config ARM_ARCH_TIMER
> bool
> select CLKSRC_OF if OF
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 56bd16e..7033b9c 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -39,6 +39,7 @@ obj-$(CONFIG_CLKSRC_EFM32) += time-efm32.o
> obj-$(CONFIG_CLKSRC_STM32) += timer-stm32.o
> obj-$(CONFIG_CLKSRC_EXYNOS_MCT) += exynos_mct.o
> obj-$(CONFIG_CLKSRC_LPC32XX) += time-lpc32xx.o
> +obj-$(CONFIG_CLKSRC_MPS2) += mps2-timer.o
> obj-$(CONFIG_CLKSRC_SAMSUNG_PWM) += samsung_pwm_timer.o
> obj-$(CONFIG_FSL_FTM_TIMER) += fsl_ftm_timer.o
> obj-$(CONFIG_VF_PIT_TIMER) += vf_pit_timer.o
> diff --git a/drivers/clocksource/mps2-timer.c b/drivers/clocksource/mps2-timer.c
> new file mode 100644
> index 0000000..77befe2
> --- /dev/null
> +++ b/drivers/clocksource/mps2-timer.c
> @@ -0,0 +1,280 @@
> +/*
> + * Copyright (C) 2015 ARM Limited
> + *
> + * Author: Vladimir Murzin <vladimir.murzin-5wv7dgnIgG8@public.gmane.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/clk.h>
> +#include <linux/clockchips.h>
> +#include <linux/clocksource.h>
> +#include <linux/err.h>
> +#include <linux/interrupt.h>
> +#include <linux/io.h>
> +#include <linux/irq.h>
> +#include <linux/of_address.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
> +#include <linux/sched_clock.h>
> +#include <linux/slab.h>
> +
> +#define TIMER_CTRL 0x0
> +#define TIMER_CTRL_ENABLE BIT(0)
> +#define TIMER_CTRL_IE BIT(3)
> +
> +#define TIMER_VALUE 0x4
> +#define TIMER_RELOAD 0x8
> +#define TIMER_INT 0xc
> +
> +struct clockevent_mps2 {
> + void __iomem *reg;
> + u32 clock_count_per_tick;
> + struct clock_event_device clkevt;
> +};
> +
> +static void __iomem *sched_clock_base;
> +
> +static u64 notrace mps2_sched_read(void)
> +{
> + return ~readl_relaxed(sched_clock_base + TIMER_VALUE);
> +}
> +
> +

extra line.

> +static inline struct clockevent_mps2 *to_mps2_clkevt(struct clock_event_device *c)
> +{
> + return container_of(c, struct clockevent_mps2, clkevt);
> +}
> +
> +static void clockevent_mps2_writel(u32 val, struct clock_event_device *c, u32 offset)
> +{
> + writel(val, to_mps2_clkevt(c)->reg + offset);
> +}
> +
> +static int mps2_timer_shutdown(struct clock_event_device *ce)
> +{
> + clockevent_mps2_writel(0, ce, TIMER_RELOAD);
> + clockevent_mps2_writel(0, ce, TIMER_CTRL);
> +
> + return 0;
> +}
> +
> +static int mps2_timer_set_next_event(unsigned long next, struct clock_event_device *ce)
> +{
> + clockevent_mps2_writel(next, ce, TIMER_VALUE);
> + clockevent_mps2_writel(TIMER_CTRL_IE | TIMER_CTRL_ENABLE, ce, TIMER_CTRL);
> +
> + return 0;
> +}
> +
> +static int mps2_timer_set_periodic(struct clock_event_device *ce)
> +{
> + u32 clock_count_per_tick = to_mps2_clkevt(ce)->clock_count_per_tick;
> +
> + clockevent_mps2_writel(clock_count_per_tick, ce, TIMER_RELOAD);
> + clockevent_mps2_writel(clock_count_per_tick, ce, TIMER_VALUE);
> + clockevent_mps2_writel(TIMER_CTRL_IE | TIMER_CTRL_ENABLE, ce, TIMER_CTRL);
> +
> + return 0;
> +}
> +
> +static irqreturn_t mps2_timer_interrupt(int irq, void *dev_id)
> +{
> + struct clockevent_mps2 *ce = dev_id;
> + u32 status = readl(ce->reg + TIMER_INT);
> +
> + if (!status)
> + return IRQ_NONE;

Why that could happen ? Add a comment.

> +
> + writel(1, ce->reg + TIMER_INT);
> +
> + ce->clkevt.event_handler(&ce->clkevt);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int __init mps2_clockevents_init(struct device_node *np)
> +{
> + void __iomem *base;
> + struct clk *clk;
> + struct irqaction *ia;
> + struct clockevent_mps2 *ce;
> + u32 rate;
> + int irq, ret;
> + const char *name = "mps2-clkevt";
> +
> + ret = of_property_read_u32(np, "clock-frequency", &rate);
> +

extra line.

> + if (ret) {
> + clk = of_clk_get(np, 0);
> + if (IS_ERR(clk)) {
> + ret = PTR_ERR(clk);
> + pr_err("failed to get clock for clockevent: %d\n", ret);
> + goto err_clk_get;
> + }
> +
> + ret = clk_prepare_enable(clk);
> + if (ret) {
> + pr_err("failed to enable clock for clockevent: %d\n", ret);
> + clk_put(clk);
> + goto err_clk_enable;
> + }
> +
> + rate = clk_get_rate(clk);
> + }
> +
> + base = of_iomap(np, 0);
> + if (!base) {
> + ret = -EADDRNOTAVAIL;
> + pr_err("failed to map register for clockevent: %d\n", ret);
> + goto err_iomap;
> + }
> +
> + irq = irq_of_parse_and_map(np, 0);
> + if (!irq) {
> + ret = -ENOENT;
> + pr_err("failed to get irq for clockevent: %d\n", ret);
> + goto err_get_irq;
> + }
> +
> + ce = kzalloc(sizeof(struct clockevent_mps2), GFP_KERNEL);
> + if (!ce) {
> + ret = -ENOMEM;
> + pr_err("failed to allocate clockevent: %d\n", ret);
> + goto err_ce_alloc;
> + }
> +
> + ce->reg = base;
> + ce->clock_count_per_tick = DIV_ROUND_CLOSEST(rate, HZ);
> + ce->clkevt.irq = irq;
> + ce->clkevt.name = name;
> + ce->clkevt.rating = 200;
> + ce->clkevt.features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
> + ce->clkevt.cpumask = cpu_possible_mask;
> + ce->clkevt.set_state_shutdown = mps2_timer_shutdown,
> + ce->clkevt.set_state_periodic = mps2_timer_set_periodic,
> + ce->clkevt.set_state_oneshot = mps2_timer_shutdown,
> + ce->clkevt.set_next_event = mps2_timer_set_next_event;
> +
> + ia = kzalloc(sizeof(struct irqaction), GFP_KERNEL);
> + if (!ia) {
> + ret = -ENOMEM;
> + pr_err("failed to allocate irqaction: %d\n", ret);
> + goto err_ia_alloc;
> + }
> +
> + ia->name = name;
> + ia->flags = IRQF_TIMER;
> + ia->handler = mps2_timer_interrupt;
> + ia->dev_id = ce;
> +
> + writel(0, base + TIMER_CTRL);
> +
> + ret = setup_irq(irq, ia);

Use request_irq here, that will save some extra code in this driver.

> + if (ret) {
> + pr_err("failed to setup irq: %d\n", ret);
> + goto err_setup_irq;
> + }
> +
> + clockevents_config_and_register(&ce->clkevt, rate, 0xf, 0xffffffff);
> +
> + return 0;
> +
> +err_setup_irq:
> + kfree(ia);
> +err_ia_alloc:
> + kfree(ce);
> +err_ce_alloc:
> +err_get_irq:
> + iounmap(base);
> +err_iomap:
> + clk_disable_unprepare(clk);
> +err_clk_enable:
> + clk_put(clk);
> +err_clk_get:
> + return ret;
> +}
> +
> +static int mps2_clocksource_init(struct device_node *np)

__init annotation.

> +{
> + void __iomem *base;
> + struct clk *clk;
> + u32 rate;
> + int ret;
> + const char *name = "mps2-clksrc";
> +
> + ret = of_property_read_u32(np, "clock-frequency", &rate);
> +

extra line.

> + if (ret) {
> + clk = of_clk_get(np, 0);
> + if (IS_ERR(clk)) {
> + ret = PTR_ERR(clk);
> + pr_err("failed to get clock for clocksource: %d\n", ret);
> + goto err_clk_get;
> + }
> +
> + ret = clk_prepare_enable(clk);
> + if (ret) {
> + pr_err("failed to enable clock for clocksource: %d\n", ret);
> + clk_put(clk);
> + goto err_clk_enable;
> + }
> +
> + rate = clk_get_rate(clk);
> + }
> +
> + base = of_iomap(np, 0);
> + if (!base) {
> + ret = -EADDRNOTAVAIL;
> + pr_err("failed to map register for clocksource: %d\n", ret);
> + goto err_iomap;
> + }
> +
> + writel(0, base + TIMER_CTRL);
> +
> + writel(0xffffffff, base + TIMER_VALUE);
> + writel(0xffffffff, base + TIMER_RELOAD);
> +
> + writel(TIMER_CTRL_ENABLE, base + TIMER_CTRL);

A comment would help to understand the above 4 lines.

> + ret = clocksource_mmio_init(base + TIMER_VALUE, name,
> + rate, 200, 32,
> + clocksource_mmio_readl_down);
> + if (ret) {
> + pr_err("failed to init clocksource: %d\n", ret);
> + goto err_clocksource_init;
> + }
> +
> + sched_clock_base = base;
> + sched_clock_register(mps2_sched_read, 32, rate);
> +
> + return 0;
> +
> +err_clocksource_init:
> + iounmap(base);
> +err_iomap:
> + clk_disable_unprepare(clk);
> +err_clk_enable:
> + clk_put(clk);
> +err_clk_get:
> + return ret;
> +

extra line.

> +}
> +
> +static void __init mps2_timer_init(struct device_node *np)
> +{
> + static int clksrc;
> +
> + if (!clksrc && !mps2_clocksource_init(np))
> + clksrc = 1;
> + else
> + mps2_clockevents_init(np);

That assumes the clocksource is defined before the clockevents in the
DT. If it is not the case, the mps2_clocksource_init will fail (and spit
errors) and mps2_clockevents_init() won't be called.

> +}
> +
> +CLOCKSOURCE_OF_DECLARE(mps2_timer, "arm,mps2-timer", mps2_timer_init);
>

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