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 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