From mboxrd@z Thu Jan 1 00:00:00 1970 From: mark.rutland@arm.com (Mark Rutland) Date: Thu, 18 Jul 2013 12:02:01 +0100 Subject: [PATCH v3] clk: add MOXA ART SoCs clock driver In-Reply-To: References: <1372943292-6960-1-git-send-email-jonas.jensen@gmail.com> <1374067396-30155-1-git-send-email-jonas.jensen@gmail.com> <20130718095035.GA29153@e106331-lin.cambridge.arm.com> Message-ID: <20130718110201.GB29153@e106331-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Thu, Jul 18, 2013 at 11:36:40AM +0100, Jonas Jensen wrote: > Hi Mark, thanks for taking a look at this. > > On 18 July 2013 11:50, Mark Rutland wrote: > > This confuses me. moxart_of_clk_init gets called because there was a > > "moxa,moxart-core-clock", node in the dt, but the driver only seems to > > use the information to figure out the configuration of another clock > > ("moxa,moxart-apb-clock"), and never registers a clock specifically for > > the core-clock. > > > > I couldn't find "moxa,moxart-apb-clock" described in mainline. COuld you > > describe the relationship between core-clock and apb-clock? > > It's true core-clock exist only so the register can be mapped. Ok. I'm just concerned that the linkage isn't explicit or obvious. > > apb-clock is part of a patch set that will add new device tree files for the > MOXA ART SoC, but it's not in mainline: > > http://lists.infradead.org/pipermail/linux-arm-kernel/2013-July/181757.html > > apb-clock could be a fixed rate 48MHz DT only clock, but because we can't > be sure it's 48MHz on all platforms, reading it from a register with core-clock > is more portable. This does leave apb-clock completely dependent on core-clock, and unless I've missed something there's no linkage between the two described in the dt. How does core-clock physically relate to apb-clock? Does it feed or is it fed by apb-clock? Are we always guaranteed to have core-clock if we have apb-clock, and is it part of the same block in hardware? If so we could describe the amalgamation as a provider with two clock outputs, with core-clock's registers for configuration at probe-time. Thanks, Mark. > > > Best regards, > Jonas >