Re: [PATCH v2 2/3] pwm: bcm2835: allow pwm driver to be used in atomic context

Ivaylo Dimitrov
2023-10-14T06:51:29Z

On 13.10.23 г. 20:51 ч., Uwe Kleine-König wrote:
> Hello,
>
> On Fri, Oct 13, 2023 at 01:13:50PM +0200, Alexander Stein wrote:
>> Am Freitag, 13. Oktober 2023, 13:04:48 CEST schrieb Stefan Wahren:
>>> Am 13.10.23 um 12:46 schrieb Sean Young:
>>>> clk_get_rate() may do a mutex lock. Since the clock rate cannot change on
>>>> an rpi, simply fetch it once.
>>>
>>> does it mean you checked all possible SoCs (BCM2835, BCM2836, BCM2837,
>>> BCM2711, BCM2712) for this change?
>>>
>>> Is it impossible that the real clock can never be influenced by turbo
>>> mode like SPI?
>>
>> Assuming the clock can change, which I would, then a clock notifier seems
>> appropriate. See [1] for an example.
>
> I'm not a fan. If the clock changes, the output also changes. With a
> clock notifier you can soften the issue and reconfigure to something
> similar as the original wave form, but a glitch happens for sure.
>

Right, but without notifier, everything rate related after the change
will be wrong

Ivo