Re: [PATCH v5 08/15] clockevents/drivers: Add STM32 Timer driver

Andy Shevchenko
2015-04-03T22:09:50Z

On Fri, Apr 3, 2015 at 8:01 PM, Maxime Coquelin
<mcoquelin.stm32@gmail.com> wrote:
> STM32 MCUs feature 16 and 32 bits general purpose timers with prescalers.
> The drivers detects whether the time is 16 or 32 bits, and applies a
> 1024 prescaler value if it is 16 bits.
>

Few comments below.

> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
> Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> ---
> drivers/clocksource/Kconfig | 8 ++
> drivers/clocksource/Makefile | 1 +
> drivers/clocksource/timer-stm32.c | 184 ++++++++++++++++++++++++++++++++++++++
> 3 files changed, 193 insertions(+)
> create mode 100644 drivers/clocksource/timer-stm32.c
>
> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
> index b82e58b..519304b 100644
> --- a/drivers/clocksource/Kconfig
> +++ b/drivers/clocksource/Kconfig
> @@ -101,6 +101,14 @@ config CLKSRC_EFM32
> Support to use the timers of EFM32 SoCs as clock source and clock
> event device.
>
> +config CLKSRC_STM32
> + bool "Clocksource for STM32 SoCs" if !ARCH_STM32
> + depends on OF && ARM && (ARCH_STM32 || COMPILE_TEST)
> + select CLKSRC_MMIO
> + default ARCH_STM32
> + help
> + Support to use the timers of STM32 SoCs as clock event device.
> +
> config ARM_ARCH_TIMER
> bool
> select CLKSRC_OF if OF
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 1c9a643..525dafe 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -35,6 +35,7 @@ obj-$(CONFIG_ARCH_NSPIRE) += zevio-timer.o
> obj-$(CONFIG_ARCH_BCM_MOBILE) += bcm_kona_timer.o
> obj-$(CONFIG_CADENCE_TTC_TIMER) += cadence_ttc_timer.o
> obj-$(CONFIG_CLKSRC_EFM32) += time-efm32.o
> +obj-$(CONFIG_CLKSRC_STM32) += timer-stm32.o
> obj-$(CONFIG_CLKSRC_EXYNOS_MCT) += exynos_mct.o
> obj-$(CONFIG_CLKSRC_SAMSUNG_PWM) += samsung_pwm_timer.o
> obj-$(CONFIG_FSL_FTM_TIMER) += fsl_ftm_timer.o
> diff --git a/drivers/clocksource/timer-stm32.c b/drivers/clocksource/timer-stm32.c
> new file mode 100644
> index 0000000..fad2e2e
> --- /dev/null
> +++ b/drivers/clocksource/timer-stm32.c
> @@ -0,0 +1,184 @@
> +/*
> + * Copyright (C) Maxime Coquelin 2015
> + * Author: Maxime Coquelin <mcoquelin.stm32@gmail.com>
> + * License terms: GNU General Public License (GPL), version 2
> + *
> + * Inspired by time-efm32.c from Uwe Kleine-Koenig
> + */
> +
> +#include <linux/kernel.h>
> +#include <linux/clocksource.h>
> +#include <linux/clockchips.h>
> +#include <linux/irq.h>
> +#include <linux/interrupt.h>
> +#include <linux/of.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/clk.h>
> +#include <linux/reset.h>
> +
> +#define TIM_CR1 0x00
> +#define TIM_DIER 0x0c
> +#define TIM_SR 0x10
> +#define TIM_EGR 0x14
> +#define TIM_PSC 0x28
> +#define TIM_ARR 0x2c
> +
> +#define TIM_CR1_CEN BIT(0)
> +#define TIM_CR1_OPM BIT(3)
> +#define TIM_CR1_ARPE BIT(7)
> +
> +#define TIM_DIER_UIE BIT(0)
> +
> +#define TIM_SR_UIF BIT(0)
> +
> +#define TIM_EGR_UG BIT(0)
> +
> +struct stm32_clock_event_ddata {
> + struct clock_event_device evtdev;
> + unsigned periodic_top;
> + void __iomem *base;
> +};
> +
> +static void stm32_clock_event_set_mode(enum clock_event_mode mode,
> + struct clock_event_device *evtdev)
> +{
> + struct stm32_clock_event_ddata *data =
> + container_of(evtdev, struct stm32_clock_event_ddata, evtdev);
> + void *base = data->base;
> +
> + switch (mode) {
> + case CLOCK_EVT_MODE_PERIODIC:
> + writel_relaxed(data->periodic_top, base + TIM_ARR);
> + writel_relaxed(TIM_CR1_ARPE | TIM_CR1_CEN, base + TIM_CR1);
> + break;
> +
> + case CLOCK_EVT_MODE_ONESHOT:
> + default:
> + writel_relaxed(0, base + TIM_CR1);
> + break;
> + }
> +}
> +
> +static int stm32_clock_event_set_next_event(unsigned long evt,
> + struct clock_event_device *evtdev)
> +{
> + struct stm32_clock_event_ddata *data =
> + container_of(evtdev, struct stm32_clock_event_ddata, evtdev);
> +
> + writel_relaxed(evt, data->base + TIM_ARR);
> + writel_relaxed(TIM_CR1_ARPE | TIM_CR1_OPM | TIM_CR1_CEN,
> + data->base + TIM_CR1);
> +
> + return 0;
> +}
> +
> +static irqreturn_t stm32_clock_event_handler(int irq, void *dev_id)
> +{
> + struct stm32_clock_event_ddata *data = dev_id;
> +
> + writel_relaxed(0, data->base + TIM_SR);
> +
> + data->evtdev.event_handler(&data->evtdev);
> +
> + return IRQ_HANDLED;
> +}
> +
> +static struct stm32_clock_event_ddata clock_event_ddata = {
> + .evtdev = {
> + .name = "stm32 clockevent",
> + .features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_PERIODIC,
> + .set_mode = stm32_clock_event_set_mode,
> + .set_next_event = stm32_clock_event_set_next_event,
> + .rating = 200,
> + },
> +};
> +
> +static void __init stm32_clockevent_init(struct device_node *np)
> +{
> + struct stm32_clock_event_ddata *data = &clock_event_ddata;
> + struct clk *clk;
> + struct reset_control *rstc;
> + unsigned long rate, max_delta;
> + int irq, ret, bits, prescaler = 1;
> +
> + 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);

Why not dev_err(); ?

> + goto err_clk_get;
> + }
> +
> + ret = clk_prepare_enable(clk);
> + if (ret) {
> + pr_err("failed to enable timer clock for clockevent (%d)\n",
> + ret);

Ditto.

> + goto err_clk_enable;
> + }
> +
> + rate = clk_get_rate(clk);
> +
> + rstc = of_reset_control_get(np, NULL);
> + if (!IS_ERR(rstc)) {
> + reset_control_assert(rstc);
> + reset_control_deassert(rstc);
> + }
> +
> + data->base = of_iomap(np, 0);
> + if (!data->base) {
> + pr_err("failed to map registers for clockevent\n");

Ditto.

> + goto err_iomap;
> + }
> +
> + irq = irq_of_parse_and_map(np, 0);
> + if (!irq) {
> + pr_err("%s: failed to get irq.\n", np->full_name);

Ditto.

> + goto err_get_irq;
> + }
> +
> + /* Detect whether the timer is 16 or 32 bits */
> + writel_relaxed(~0UL, data->base + TIM_ARR);
> + max_delta = readl_relaxed(data->base + TIM_ARR);
> + if (max_delta == ~0UL) {
> + prescaler = 1;
> + bits = 32;
> + } else {
> + prescaler = 1024;
> + bits = 16;
> + }
> + writel_relaxed(0, data->base + TIM_ARR);
> +
> + writel_relaxed(prescaler - 1, data->base + TIM_PSC);
> + writel_relaxed(TIM_EGR_UG, data->base + TIM_EGR);
> + writel_relaxed(TIM_DIER_UIE, data->base + TIM_DIER);
> + writel_relaxed(0, data->base + TIM_SR);
> +
> + data->periodic_top = DIV_ROUND_CLOSEST(rate, prescaler * HZ);
> +
> + clockevents_config_and_register(&data->evtdev,
> + DIV_ROUND_CLOSEST(rate, prescaler),
> + 0x1, max_delta);
> +
> + ret = request_irq(irq, stm32_clock_event_handler, IRQF_TIMER,
> + "stm32 clockevent", data);
> + if (ret) {
> + pr_err("%s: failed to request irq.\n", np->full_name);

Ditto.

> + goto err_get_irq;
> + }
> +
> + pr_info("%s: STM32 clockevent driver initialized (%d bits)\n",
> + np->full_name, bits);

dev_info(); ?

> +
> + return;
> +
> +err_get_irq:
> + iounmap(data->base);
> +err_iomap:
> + clk_disable_unprepare(clk);
> +err_clk_enable:
> + clk_put(clk);
> +err_clk_get:
> + return;
> +}
> +
> +CLOCKSOURCE_OF_DECLARE(stm32, "st,stm32-timer", stm32_clockevent_init);
> --
> 1.9.1
>

--
With Best Regards,
Andy Shevchenko