On Thu, May 10, 2012 at 7:41 AM, Sascha Hauer <s.ha...@pengutronix.de> wrote: > On Wed, May 09, 2012 at 09:27:02AM -0500, Rob Lee wrote: >> Sascha, >> >> > >> > This clk_get should go away here and be moved somewhere to >> > initialization. Also, if getting this clock fails we can still >> > do regular cpu_do_idle. Additionally, if clk_get fails, we'll >> > have a ERR_PTR value in gpc_dvfs_clk in which case the >> > gpc_dvfs_clk == NULL won't trigger next time you are here and >> > then you'll enable a nonexisting clock below. >> > >> >> Agree. I'd prefer to enable this clock during intialization and just >> leave it running. It is supposed to be a very low power clock and I >> couldn't measuring any power difference with and without it being >> enabled > > Ok, even better. > >> > >> > I wonder why you don't add the default ARM_CPUIDLE_WFI_STATE_PWR state. >> > The above is something different, right? It has a greater exit latency >> > than ARM_CPUIDLE_WFI_STATE_PWR, so why don't we add it here aswell? >> >> Yes and no. Yes this is a different state but no, it doesn't have a >> significantly greater exit latency, or at least a large enough exit >> latency to warrant an extra state in my opinion. According to the >> i.MX5 documentation, the extra exit time beyond basic WFI required for >> the "WAIT_UNCLOCKED_POWER_OFF" state is 500ns (this is due to a >> difference in i.MX5 hardware implementation compared to all other ARM >> platforms). In reality, it did require a few more microseconds to >> perform in my testing just based on the extra register writes in >> mx5_cpu_lp_set(). I'd like to clean up mx5_cpu_lp_set() and add a >> global variable to track the previous state and to just exit out if >> the new state is the same as the old. > > Do you think it's worth it? You buy skipping the read with an additional > test. >
I'll run some tests to check. Thanks, Rob >> I could do this cleanup as part of this patchset if you prefer that. > > Yes please. Cleanups before adding new features is always a good reason > to apply a patch series ;) > > Sascha > > -- > Pengutronix e.K. | | > Industrial Linux Solutions | http://www.pengutronix.de/ | > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | > Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ linaro-dev mailing list linaro-dev@lists.linaro.org http://lists.linaro.org/mailman/listinfo/linaro-dev
