From mboxrd@z Thu Jan 1 00:00:00 1970 From: haojian.zhuang@gmail.com (Haojian Zhuang) Date: Mon, 6 Sep 2010 19:42:18 +0800 Subject: Colibri PXA320 Power management question In-Reply-To: <20100906113036.GG10367@rakim.wolfsonmicro.main> References: <20100902142203.GA8381@sirena.org.uk> <4C7FB7B5.2010301@compulab.co.il> <20100902152705.GC5809@rakim.wolfsonmicro.main> <4C7FC606.20904@compulab.co.il> <20100906101320.GD10367@rakim.wolfsonmicro.main> <20100906113036.GG10367@rakim.wolfsonmicro.main> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Mon, Sep 6, 2010 at 7:30 PM, Mark Brown wrote: > On Mon, Sep 06, 2010 at 07:09:44PM +0800, Eric Miao wrote: >> On Mon, Sep 6, 2010 at 6:13 PM, Mark Brown > >> > That'd be slightly entertaining, though, since IIRC the hardware >> > implementation isn't really set up for being constrained - it doesn't >> > expect to be cooperating with software governors. > >> It doesn't need to. There is actually an internal command table, and >> not really sure about the mapping scheme though, but when software >> then has only to care about the frequencies, and voltages will be >> adjusted accordingly. > > Ah, I'm misremembering the PXA implementation for the i.MX one - the > i.MX version of this feature had a governor rather than just doing a > lookup from the frequency to a voltage. > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel > I think that the key isn't scaling voltage. We can enable both auto-scaling (hardware) and software-scaling voltage in cpufreq driver. The key point is that device may occur fails while scaling frequency in device working mode. I remember that cpufreq doesn't care about this behavior.