From mboxrd@z Thu Jan 1 00:00:00 1970 From: ccross@google.com (Colin Cross) Date: Wed, 4 May 2011 23:50:52 -0700 Subject: Common clock and dvfs In-Reply-To: References: <4DC07F10.6010305@ti.com> <4DC230E0.7090909@ti.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, May 4, 2011 at 11:35 PM, Paul Walmsley wrote: > On Wed, 4 May 2011, Colin Cross wrote: > >> Imagine a chip where a clock can feed devices A, B, and C. ?If the >> devices are always clocked at the same rate, and can't gate their >> clocks, the minimum voltage that can be applied to a rail is >> determined ONLY by the rate of the clock. > > That's not so -- although admittedly it's a side issue, and not > particularly related to DVFS. > > For example, the device may have some external I/O lines which need to be > at least some minimum voltage level for the externally-connected device to > function. ?This minimum voltage level can be unrelated to the device's > clock frequency. True, that was an oversimplificaiton. I meant the minimum voltage that scales with clock frequencies only depends on the clock frequency, not the device. Devices do need to be able to specify a higher minimum voltage, and the regulator api needs to handle it.