Re: [RFC v6 01/23] clocksource: sh_cmt: compute rate before registration again

Nicolai Stange
2016-09-10T19:12:12Z

Thomas Gleixner <tglx@linutronix.de> writes:

> On Fri, 9 Sep 2016, Nicolai Stange wrote:
>> @@ -339,17 +339,14 @@ static int sh_cmt_enable(struct sh_cmt_channel *ch, unsigned long *rate)
>> sh_cmt_start_stop_ch(ch, 0);
>>
>> /* configure channel, periodic mode and maximum timeout */
>> - if (ch->cmt->info->width == 16) {
>> - *rate = clk_get_rate(ch->cmt->clk) / 512;
>> + if (ch->cmt->info->width == 16)
>> sh_cmt_write_cmcsr(ch, SH_CMT16_CMCSR_CMIE |
>> SH_CMT16_CMCSR_CKS512);
>> - } else {
>> - *rate = clk_get_rate(ch->cmt->clk) / 8;
>> + else
>> sh_cmt_write_cmcsr(ch, SH_CMT32_CMCSR_CMM |
>> SH_CMT32_CMCSR_CMTOUT_IE |
>> SH_CMT32_CMCSR_CMR_IRQ |
>> SH_CMT32_CMCSR_CKS_RCLK8);
>> - }
>
> Removing the braces here is just wrong.

Completely convinced, will redo.

>> @@ -824,6 +810,12 @@ static int sh_cmt_register_clockevent(struct sh_cmt_channel *ch,
>> ced->suspend = sh_cmt_clock_event_suspend;
>> ced->resume = sh_cmt_clock_event_resume;
>>
>> + /* TODO: calculate good shift from rate and counter bit width */
>> + ced->shift = 32;
>> + ced->mult = div_sc(ch->cmt->rate, NSEC_PER_SEC, ced->shift);
>
>
> Errm. clockevents_calc_mult_shift()

Or even clockevents_config_and_register()?

The reason why I left this mult/shift initialization as is (it has only
been moved from sh_cmt_clock_event_start() by this patch) is that I was
unsure about why this conversion hadn't been done before. That TODO
comment seems to imply that a shift value as calculated by
clockevents_config() isn't always the perfect choice...

However, do you want me to
a.) simply change this patch to use clockevents_config_and_register(),
b.) add a separate patch to this series doing this cleanup,
c.) send such a patch on its own
d.) or leave this initalization as is?

Thanks,

Nicolai Stange