linux-kernel - Re: [PATCH v2 3/6] clocksource/drivers/tegra: Set and use timer's period

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Date:   Tue, 18 Jun 2019 12:41:15 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Joseph Lo <josephl@...dia.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Peter De Schrijver <pdeschrijver@...dia.com>
Cc:     linux-tegra@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/6] clocksource/drivers/tegra: Set and use timer's
 period

18.06.2019 11:40, Jon Hunter пишет:
> 
> On 17/06/2019 15:04, Dmitry Osipenko wrote:
>> 17.06.2019 13:51, Jon Hunter пишет:
>>>
>>> On 14/06/2019 17:45, Dmitry Osipenko wrote:
>>>> 14.06.2019 18:48, Jon Hunter пишет:
>>>>>
>>>>> On 10/06/2019 17:43, Dmitry Osipenko wrote:
>>>>>> The of_clk structure has a period field that is set up initially by
>>>>>> timer_of_clk_init(), that period value need to be adjusted for a case of
>>>>>> TIMER1-9 that are running at a fixed rate that doesn't match the clock's
>>>>>> rate. Note that the period value is currently used only by some of the
>>>>>> clocksource drivers internally and hence this is just a minor cleanup
>>>>>> change that doesn't fix anything.
>>>>>>
>>>>>> Signed-off-by: Dmitry Osipenko <digetx@...il.com>
>>>>>> ---
>>>>>>  drivers/clocksource/timer-tegra.c | 5 +++--
>>>>>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/clocksource/timer-tegra.c b/drivers/clocksource/timer-tegra.c
>>>>>> index 810b4e7435cf..646b3530c2d2 100644
>>>>>> --- a/drivers/clocksource/timer-tegra.c
>>>>>> +++ b/drivers/clocksource/timer-tegra.c
>>>>>> @@ -71,9 +71,9 @@ static int tegra_timer_shutdown(struct clock_event_device *evt)
>>>>>>  static int tegra_timer_set_periodic(struct clock_event_device *evt)
>>>>>>  {
>>>>>>  	void __iomem *reg_base = timer_of_base(to_timer_of(evt));
>>>>>> +	unsigned long period = timer_of_period(to_timer_of(evt));
>>>>>>  
>>>>>> -	writel_relaxed(TIMER_PTV_EN | TIMER_PTV_PER |
>>>>>> -		       ((timer_of_rate(to_timer_of(evt)) / HZ) - 1),
>>>>>> +	writel_relaxed(TIMER_PTV_EN | TIMER_PTV_PER | (period - 1),
>>>>>>  		       reg_base + TIMER_PTV);
>>>>>>  
>>>>>>  	return 0;
>>>>>> @@ -297,6 +297,7 @@ static int __init tegra_init_timer(struct device_node *np, bool tegra20,
>>>>>>  		cpu_to->clkevt.rating = rating;
>>>>>>  		cpu_to->clkevt.cpumask = cpumask_of(cpu);
>>>>>>  		cpu_to->of_base.base = timer_reg_base + base;
>>>>>> +		cpu_to->of_clk.period = DIV_ROUND_UP(rate, HZ);
>>>>>
>>>>> Any reason you made this a round-up?
>>>>
>>>> That's what timer_of_clk_init() does, I assume it should be a more correct variant.
>>>
>>> Sounds to me like this should be 2 patches, because you are changing the
>>> value. This is not just purely cleanup IMO.
>>
>> Indeed, that could be at least mentioned in the commit message. Probably I just
>> assumed that this is such a minor change that not worth anything. A hundred of
>> microseconds is hardly noticeable.
>>
>> I'm not really sure if this really worth a re-spin at this point. Jon, are you insisting?
> 
> At a minimum the changelog needs to be udpated to reflect what is going
> on here. Yes it may not be a massive difference, but I prefer not to
> change things without any rationale.

Okay, I'll respin this series and probably will just drop the round-up. I'll also
append the other two new patches "cycles can't be 0" and "max limit correction" to
this series.

Daniel, I'll also correct the "Fixes" tag to satisfy the linux-next patch checker.