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

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Date:   Fri, 14 Jun 2019 19:45:48 +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

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.