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

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Message-ID: <5655CADA.1010803@arm.com>
Date:	Wed, 25 Nov 2015 14:51:06 +0000
From:	Vladimir Murzin <vladimir.murzin@....com>
To:	Daniel Lezcano <daniel.lezcano@...aro.org>, arnd@...db.de,
	linux@....linux.org.uk, gregkh@...uxfoundation.org,
	tglx@...utronix.de, u.kleine-koenig@...gutronix.de,
	afaerber@...e.de, mcoquelin.stm32@...il.com
CC:	Mark.Rutland@....com, Pawel.Moll@....com,
	ijc+devicetree@...lion.org.uk, galak@...eaurora.org,
	jslaby@...e.cz, robh+dt@...nel.org, devicetree@...r.kernel.org,
	linux-serial@...r.kernel.org, linux-api@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 02/10] clockevents/drivers: add MPS2 Timer driver

Hi Daniel,

Thanks for you review, I agree on all concerns raised and address them
in the next version. Just some points to confirm below (I left only
relevant parts).

>> +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.
> 

Sort of defensive programming, I never seen it happens, but just in case
of spurious interrupts... Do you prefer to get rid of this check or

    /* spurious interrupt? */
    if (!status)
        return IRQ_NONE;

would be fine to you?

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

Does following (stolen from efm32) look better to you?

static void __init mps2_timer_init(struct device_node *np)
{
	static int has_clocksource, has_clockevent;
	int ret;

	if (!has_clocksource) {
		ret = mps2_clocksource_init(np);
		if (!ret) {
			has_clocksource = 1;
			return;
		}
	}

	if (!has_clockevent) {
		ret = mps2_clockevent_init(np);
		if (!ret) {
			has_clockevent = 1;
			return;
		}
	}
}

Thanks
Vladimir

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

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