linux-kernel - Re: [PATCH v3 2/2] clocksource: driver for Conexant Digicolor SoC timer

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Date:	Sun, 25 Jan 2015 16:03:03 +0100
From:	Daniel Lezcano <daniel.lezcano@...aro.org>
To:	Baruch Siach <baruch@...s.co.il>
CC:	Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v3 2/2] clocksource: driver for Conexant Digicolor SoC
 timer

On 01/25/2015 03:46 PM, Baruch Siach wrote:
> Hi Daniel,
>
> On Thu, Jan 22, 2015 at 01:54:39PM +0100, Daniel Lezcano wrote:
>> On 01/21/2015 07:36 AM, Baruch Siach wrote:
>>> + * Based on:
>>> + *	Allwinner SoCs hstimer driver
>>
>> If this is based on the Allwinnner driver, may be you can have a look at the
>> patchset sent by Maxim to make sure your implementation is complete ?
>>
>> https://lkml.org/lkml/2015/1/11/52
>
> Thanks for the tip. I'll take the applicable parts from that series.
>
> [...]
>
>>> +static void __iomem *timer_base;
>>> +static u32 ticks_per_jiffy;
>>
>> Mind to encapsulate those global variables in a structure and use
>> container_of to access those fields like:
>>
>> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/clocksource/mtk_timer.c#n56
>>
>> ?
>
> The trouble is that the sched_clock callback (digicolor_timer_sched_read)
> needs a static timer_base to find the timer counter. Do you think adding a
> structure is worth it only for ticks_per_jiffy?

Well you will have to define the global variable for this structure. So 
you should be able to access the timer base directly. I agree it is not 
perfect but at least that will encapsulate the code for the clockevents 
side.

>>> +static void digicolor_clkevt_mode(enum clock_event_mode mode,
>>> +				  struct clock_event_device *clk)
>>> +{
>>> +	switch (mode) {
>>> +	case CLOCK_EVT_MODE_PERIODIC:
>>> +		writeb(0, timer_base + CONTROL(TIMER_C));
>>
>> Even if that sounds overkill, please replace '0', '1' with whatever macro
>> name (eg. TIMER_DISABLE/ENABLE).
>
> Will do for the entire file.
>
> [...]
>
>>> +static struct irqaction digicolor_timer_irq = {
>>> +	.name = "digicolor_timerC",
>>> +	.flags = IRQF_TIMER | IRQF_IRQPOLL,
>>> +	.handler = digicolor_timer_interrupt,
>>> +	.dev_id = &digicolor_clockevent,
>>> +};
>>
>> The current trend is to use 'request_irq', so no such structure
>> declaration/initialization is needed.
>
> Thanks. Will do.
>
>>> +	writel(~0, timer_base + COUNT(TIMER_B));
>>
>> s/~0/UINT_MAX/ ?
>
> Ack.
>
> Thanks for reviewing. I'll post an updated series shortly.

Ok, thanks.

   -- Daniel


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