On Tue, Nov 28, 2017 at 09:02:52PM +0100, Ladislav Michl wrote: > On Tue, Nov 28, 2017 at 12:09:06PM -0600, Grygorii Strashko wrote: > > > > > > On 11/23/2017 05:06 AM, Ladislav Michl wrote: > > > On Thu, Nov 23, 2017 at 11:26:04AM +0100, Ladislav Michl wrote: > > > > On Thu, Nov 23, 2017 at 10:35:42AM +0100, Ladislav Michl wrote: > > > > > On Thu, Nov 16, 2017 at 03:04:48PM -0600, Grygorii Strashko wrote: > > > > > [snip] > > > > > > I recommend to disable CPU idle completely in config and re-check test, > > > > > > before continue with other things. > > > > > > > > > > Strangely enough latency is much worse with CONFIG_CPU_IDLE disabled. > > > > > > > > While it is better with: > > > > CONFIG_HZ_PERIODIC=y > > > > CONFIG_CPU_FREQ=n > > > > CONFIG_PM=n > > > > > > > > But both ehci and musb does not see any device connected and: > > > [snip] > > > > > > The culprit here is CONFIG_PM. With CONFIG_PM disabled latency jitter is > > > about 30us, which is pretty good for general purpose OS. But some drivers > > > do not work without CONFIG_PM. Suggestions? > > > > Not sure OMAP ever expected to fully work with CONFIG_PM=n > > > > You can try play with HWMOD props, like add flags to gpio hwmods: > > HWMOD_NO_OCP_AUTOIDLE > > HWMOD_NO_IDLE > > HWMOD_CLKDM_NOAUTO > > And that did the trick! Well, almost. 'ti,no-idle' to gpio5 node and Tony's > suggestion to allow only C1 cpuidle state gives almost as good jitter as > with CONFIG_PM disabled. > > Just out of curiosity, I'll try with -rt patch. So after more testing it seems GPIO is a dead end. The jitter is just too big to diferentiate all those IR protocols. Options are to use FIQ, read timestamp from hw timer and queue it using ringbuffer or something similar. Or solder wire on board and connect it to dmtimer capture input. This was tested and seems to get very reasonable results (as one would expect from hw dedicated for that purpose). As later solution will be most likely used, I'd like to thank everyone who helped with suggestions and will have more questions in Keerthy's dmtimer patch series. Best regards, ladis -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
