Subject: [PATCH 1/3] clocksource: timer-keystone: introduce clocksource driver for Keystone

From: [email-masked] (Daniel Lezcano)
Date: Thu, 12 Dec 2013 16:51:20 +0100

On 12/11/2013 07:00 PM, Ivan Khoronzhuk wrote:
> Add broadcast clock-event device for the Keystone arch.
>
> The timer can be configured as a general-purpose 64-bit timer,
> dual general-purpose 32-bit timers. When configured as dual 32-bit
> timers, each half can operate in conjunction (chain mode) or
> independently (unchained mode) of each other.
>
> Signed-off-by: Ivan Khoronzhuk <[email-masked]>
> ---
>   drivers/clocksource/Makefile         |    1 +
>   drivers/clocksource/timer-keystone.c |  223 ++++++++++++++++++++++++++++++++++
>   2 files changed, 224 insertions(+)
>   create mode 100644 drivers/clocksource/timer-keystone.c
>
> diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
> index 33621ef..2acf3fc 100644
> --- a/drivers/clocksource/Makefile
> +++ b/drivers/clocksource/Makefile
> @@ -36,3 +36,4 @@ obj-$(CONFIG_ARM_ARCH_TIMER)		+= arm_arch_timer.o
>   obj-$(CONFIG_ARM_GLOBAL_TIMER)		+= arm_global_timer.o
>   obj-$(CONFIG_CLKSRC_METAG_GENERIC)	+= metag_generic.o
>   obj-$(CONFIG_ARCH_HAS_TICK_BROADCAST)	+= dummy_timer.o
> +obj-$(CONFIG_ARCH_KEYSTONE)		+= timer-keystone.o
> diff --git a/drivers/clocksource/timer-keystone.c b/drivers/clocksource/timer-keystone.c
> new file mode 100644
> index 0000000..4a8083a
> --- /dev/null
> +++ b/drivers/clocksource/timer-keystone.c
> @@ -0,0 +1,223 @@
> +/*
> + * Keystone broadcast clock-event
> + *
> + * Copyright 2013 Texas Instruments, Inc.
> + *
> + * Author: Ivan Khoronzhuk <[email-masked]>
> + *
> + * 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.
> + *
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/clockchips.h>
> +#include <linux/clocksource.h>
> +#include <linux/interrupt.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +
> +#define TIMER_NAME			"timer64-event"
> +
> +/* Timer register offsets */
> +#define TIM12				0x10
> +#define TIM34				0x14
> +#define PRD12				0x18
> +#define PRD34				0x1c
> +#define TCR				0x20
> +#define TGCR				0x24
> +#define INTCTLSTAT			0x44
> +
> +/* Timer register bitfields */
> +#define TCR_ENAMODE_MASK		0xC0
> +#define TCR_ENAMODE_ONESHOT_MASK	0x40
> +#define TCR_ENAMODE_PERIODIC_MASK	0x80
> +
> +#define TGCR_TIM_UNRESET_MASK		0x03
> +#define INTCTLSTAT_ENINT_MASK		0x01
> +
> +/**
> + * struct keystone_timer: holds timer's data
> + * @base: timer memory base address
> + * @clk_rate: source clock rate
> + * @irqacrion: interrupt action descriptor
> + * @event_dev: event device based on timer
> + */
> +static struct keystone_timer {
> +	void __iomem *base;
> +	unsigned long clk_rate;
> +	struct irqaction irqaction;
> +	struct clock_event_device event_dev;
> +} timer;
> +
> +static inline u32 keystone_timer_readl(unsigned long rg)
> +{
> +	return readl(timer.base + rg);
> +}
> +
> +static inline void keystone_timer_writel(u32 val, unsigned long rg)
> +{
> +	writel(val, timer.base + rg);
> +}
> +
> +/**
> + * keystone_timer_config: configures timer to work in oneshot/periodic modes, in
> + * other cases disables timer.
> + * @ mode: mode to configure
> + * @ period: cycles number to configure for
> + */
> +static int keystone_timer_config(u64 period, enum clock_event_mode mode)
> +{
> +	u32 tcr;
> +
> +	tcr = keystone_timer_readl(TCR);
> +
> +	/* disable timer */
> +	tcr &= ~(TCR_ENAMODE_MASK);
> +	keystone_timer_writel(tcr, TCR);

Please move this write after the switch (cf. linked comment below)

> +	/* set enable mode or leave disabled timer */
> +	switch (mode) {
> +	case CLOCK_EVT_MODE_ONESHOT:
> +		tcr |= TCR_ENAMODE_ONESHOT_MASK;
> +		break;
> +	case CLOCK_EVT_MODE_PERIODIC:
> +		tcr |= TCR_ENAMODE_PERIODIC_MASK;
> +		break;
> +	default:
> +		return 0;

Shouldn't you return an error ?

> +	}
> +
> +	/* reset counter to zero, set new period */
> +	keystone_timer_writel(0, TIM12);
> +	keystone_timer_writel(0, TIM34);
> +	keystone_timer_writel(period & 0xffffffff, PRD12);
> +	keystone_timer_writel(period >> 32, PRD34);
> +
> +	/* enable timer */
> +	keystone_timer_writel(tcr, TCR);
> +	return 0;
> +}
> +
> +static irqreturn_t keystone_timer_interrupt(int irq, void *dev_id)
> +{
> +	struct clock_event_device *evt = &timer.event_dev;
> +
> +	evt->event_handler(evt);
> +	return IRQ_HANDLED;
> +}
> +
> +static int keystone_set_next_event(unsigned long cycles,
> +				  struct clock_event_device *evt)
> +{
> +	return keystone_timer_config(cycles, evt->mode);
> +}
> +
> +static void keystone_set_mode(enum clock_event_mode mode,
> +			     struct clock_event_device *evt)
> +{
> +	u64 period;
> +
> +	switch (mode) {
> +	case CLOCK_EVT_MODE_PERIODIC:
> +		period = timer.clk_rate / (HZ);
> +		keystone_timer_config(period, CLOCK_EVT_MODE_PERIODIC);
> +		break;
> +	case CLOCK_EVT_MODE_UNUSED:
> +	case CLOCK_EVT_MODE_SHUTDOWN:
> +	case CLOCK_EVT_MODE_ONESHOT:
> +		keystone_timer_config(0, CLOCK_EVT_MODE_SHUTDOWN);

I don't really this code assuming the side effect of specifying a 
unsupported mode will disable the timer.

> +	default:
> +		break;
> +	}
> +}
> +
> +static void __init keystone_timer_init(struct device_node *np)
> +{
> +	struct clock_event_device *event_dev = &timer.event_dev;
> +	struct irqaction *irqaction = &timer.irqaction;
> +	unsigned long rate;
> +	struct clk *clk;
> +	int irq, error;
> +	u32 tgcr;
> +
> +	irq  = irq_of_parse_and_map(np, 0);
> +	if (irq == NO_IRQ) {
> +		pr_err("%s: failed to map interrupts\n", __func__);
> +		return;
> +	}
> +
> +	timer.base = of_iomap(np, 0);
> +	if (!timer.base) {
> +		pr_err("%s: failed to map registers\n", __func__);
> +		return;
> +	}
> +
> +	clk = of_clk_get(np, 0);
> +	if (!clk) {
> +		pr_err("%s: failed to get clock\n", __func__);
> +		iounmap(timer.base);
> +		return;
> +	}
> +
> +	error = clk_prepare_enable(clk);
> +	if (error) {
> +		pr_err("%s: failed to enable clock\n", __func__);
> +		goto err;
> +	}
> +
> +	rate = clk_get_rate(clk);
> +
> +	/* disable, use internal clock source */
> +	keystone_timer_writel(0, TCR);
> +
> +	/* reset timer as 64-bit, no pre-scaler, plus features are disabled */
> +	tgcr = 0;
> +	keystone_timer_writel(0, TGCR);
> +
> +	/* unreset timer */
> +	tgcr |= TGCR_TIM_UNRESET_MASK;
> +	keystone_timer_writel(tgcr, TGCR);
> +
> +	/* init counter to zero */
> +	keystone_timer_writel(0, TIM12);
> +	keystone_timer_writel(0, TIM34);
> +
> +	timer.clk_rate = rate;
> +
> +	/* enable timer interrupts */
> +	keystone_timer_writel(INTCTLSTAT_ENINT_MASK, INTCTLSTAT);
> +
> +	keystone_timer_config(0, CLOCK_EVT_MODE_UNUSED);

Same comment here.

> +	/* init irqaction */
> +	irqaction->flags = IRQF_TIMER;
> +	irqaction->handler = keystone_timer_interrupt;
> +	irqaction->name = TIMER_NAME;
> +	irqaction->dev_id = (void *)&timer;
> +	error = setup_irq(irq, irqaction);
> +	if (error) {
> +		pr_err("%s: failed to setup irq\n", __func__);
> +		goto err;
> +	}
> +
> +	/* setup clockevent */
> +	event_dev->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT;
> +	event_dev->set_next_event = keystone_set_next_event;
> +	event_dev->set_mode = keystone_set_mode;
> +	event_dev->cpumask = cpu_all_mask;
> +	event_dev->owner = THIS_MODULE;
> +	event_dev->name = TIMER_NAME;
> +
> +	clockevents_config_and_register(event_dev, rate, 1, ULONG_MAX);
> +
> +	pr_info("keystone timer clock @%lu Hz\n", rate);
> +	return;
> +err:
> +	clk_put(clk);
> +	iounmap(timer.base);
> +}
> +
> +CLOCKSOURCE_OF_DECLARE(keystone_timer, "ti,keystone-timer",
> +					keystone_timer_init);
>

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