linux-kernel - Re: [PATCH v5 2/4] clocksource: stm32: only use 32 bits timers

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Date:   Wed, 18 Oct 2017 14:25:18 +0200
From:   Benjamin Gaignard <benjamin.gaignard@...aro.org>
To:     Julien Thierry <julien.thierry@....com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ludovic Barre <ludovic.barre@...com>,
        devicetree@...r.kernel.org,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/4] clocksource: stm32: only use 32 bits timers

2017-10-18 10:21 GMT+02:00 Julien Thierry <julien.thierry@....com>:
>
>
> On 18/10/17 08:43, Benjamin Gaignard wrote:
>>
>> 16 bits hardware are not enough accure to be used.
>> Do no allow them to be probed by tested max counter value.
>>
>> Signed-off-by: Benjamin Gaignard <benjamin.gaignard@...aro.org>
>> ---
>>   drivers/clocksource/timer-stm32.c | 23 +++++++++--------------
>>   1 file changed, 9 insertions(+), 14 deletions(-)
>>
>> diff --git a/drivers/clocksource/timer-stm32.c
>> b/drivers/clocksource/timer-stm32.c
>> index abff21c..f7e4eec 100644
>> --- a/drivers/clocksource/timer-stm32.c
>> +++ b/drivers/clocksource/timer-stm32.c
>> @@ -81,9 +81,9 @@ static irqreturn_t stm32_clock_event_handler(int irq,
>> void *dev_id)
>>   static int __init stm32_clockevent_init(struct device_node *node)
>>   {
>>         struct reset_control *rstc;
>> -       unsigned long max_delta;
>> -       int ret, bits, prescaler = 1;
>> +       unsigned long max_arr;
>>         struct timer_of *to;
>> +       int ret;
>>         to = kzalloc(sizeof(*to), GFP_KERNEL);
>>         if (!to)
>> @@ -113,26 +113,21 @@ static int __init stm32_clockevent_init(struct
>> device_node *node)
>>         /* Detect whether the timer is 16 or 32 bits */
>>         writel_relaxed(~0U, timer_of_base(to) + TIM_ARR);
>> -       max_delta = readl_relaxed(timer_of_base(to) + TIM_ARR);
>> -       if (max_delta == ~0U) {
>> -               prescaler = 1;
>> -               bits = 32;
>> -       } else {
>> -               prescaler = 1024;
>> -               bits = 16;
>> +       max_arr = readl_relaxed(timer_of_base(to) + TIM_ARR);
>> +       if (max_arr != ~0U) {
>> +               pr_err("32 bits timer is needed\n");
>> +               return -EINVAL;
>
>
> Same as with previous patch, I think "to" should get freed.

Yes I could solve that in the first patch

>
> Also, why is there no function to undo what timer_of_init did? Shouldn't we
> be able to free the irqs and unmap the timer io base here?

timer-of doesn't provide deinit function since I will have to do a new version
I will add it.

Benjamin
>
> Cheers,
>
> --
> Julien Thierry