On Mon, Sep 25, 2023 at 07:06:44PM +0300, Ivaylo Dimitrov wrote: > On 1.09.23 г. 17:18 ч., Sean Young wrote: > > The ir-rx51 is a pwm-based TX driver specific to the N900. This can be > > handled entirely by the generic pwm-ir-tx driver, and in fact the > > pwm-ir-tx driver has been compatible with ir-rx51 from the start. > > > > Unfortunately, pwm-ir-tx does not work on n900. My investigation shows that > for some reason usleep_range() sleeps for at least 300-400 us more than what > interval it is requested to sleep. I played with cyclictest from rt-tests > package and it gives similar results - increasing the priority helps, but I > was not able to make it sleep for less that 300 us in average. I tried > cpu_latency_qos_add_request() in pwm-ir-tx, but it made no difference. > > I get similar results on motorola droid4 (OMAP4), albeit there average sleep > is in 200-300 us range, which makes me believe that either OMAPs have issues > with hrtimers or the config we use has some issue which leads to scheduler > latency. Or, something else... The pwm-ir-tx driver does suffer from this problem, but I was under the impression that the ir-rx51 has the same problem. > In either case help is appreciated to dig further trying to find the reason > for such a big delay. pwm-ir-tx uses usleep_range() and ir-rx51 uses hrtimers. I thought that usleep_range() uses hrtimers; however if you're not seeing the same delay on ir-rx51 then maybe it's time to switch pwm-ir-tx to hrtimers. I don't have a n900 to test on, unfortunately. Thanks Sean
