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

From: [email-masked] (ivan.khoronzhuk)
Date: Thu, 12 Dec 2013 19:36:51 +0200

On 12/12/2013 05:51 PM, Daniel Lezcano wrote:
> 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)
> 

See 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 ?
> 

It returns value only for convenient usage in keystone_set_next_event(),
see [1].

In general, this function is used to configure the timer.
The procedure is that we need to stop the timer then set it.
If timer needs to be disabled (shutdown mode), function disables it and returns.

>> +    }
>> +
>> +    /* 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);

[1]

>> +}
>> +
>> +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.
> 

In case of an unsupported mode the function does nothing.
Is it not correct?

It disables the timer only in 3 cases.
CLOCK_EVT_MODE_UNUSED
CLOCK_EVT_MODE_SHUTDOWN
CLOCK_EVT_MODE_ONESHOT

For CLOCK_EVT_MODE_ONESHOT,
It is supposed that then keystone_set_next_even() will re-enable 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.
> 

you are right, I disabled the timer above.., so
I may delete "keystone_timer_config(0, CLOCK_EVT_MODE_UNUSED);"

>> +    /* 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);
>>
> 
> 

-- 
Regards,
Ivan Khoronzhuk