Hi Robin, >-----Original Message----- >From: linux-arm-kernel [mailto:linux-arm-kernel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Robin Murphy >Sent: Wednesday, February 08, 2017 8:01 PM >To: Mark Rutland <mark.rutland@xxxxxxx>; Sricharan <sricharan@xxxxxxxxxxxxxx> >Cc: devicetree@xxxxxxxxxxxxxxx; mathieu.poirier@xxxxxxxxxx; linux-arm-msm@xxxxxxxxxxxxxxx; joro@xxxxxxxxxx; >will.deacon@xxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx; sboyd@xxxxxxxxxxxxxx; linux-arm- >kernel@xxxxxxxxxxxxxxxxxxx; m.szyprowski@xxxxxxxxxxx >Subject: Re: [PATCH V2 1/3] iommu/arm-smmu: Add pm_runtime/sleep ops > >On 08/02/17 13:52, Mark Rutland wrote: >> On Wed, Feb 08, 2017 at 07:15:37PM +0530, Sricharan wrote: >>>> Clocks are not architectural, so it only makes sense to associate them >>>> with an implementation-specific compatible string. There's also no >>> >>> ok, it for this the QCOM specific implementation binding is tried(going to). >>> >>>> guarantee that different microarchitectures have equivalent internal >>>> clock domains - I'm not sure if "the SMMU's underlying bus access" is >>>> meant to refer to accesses *by* the SMMU, i.e. page table walks, >>>> accesses *through* the SMMU by upstream masters, or both >>> >>> In the above QCOM case, it is actually both. Its the same path for both the >>> page table walker and upstream masters. > >Right, that's what I feared. As far as I can make out the current ARM >implementations, transactions passing through will require at least >TBUn_BCLK for the appropriate TBU, but would also need the page table >walker clocked with CCLK to resolve TLB misses. But then the programming >interface is also in the CCLK domain (not counting the incoming APB or >AXI clock for the actual slave port itself). Thus this 'generic' clock >binding already isn't compatible with MMU-40x/500. > Right, this implementation's clock bindings are not going to compatible with MMU-500. There is also another soc which integrates MMU-500. So will have to add the clock bindings for MMU-500 as well separately. Also in MMU-500 i saw that there is a possibility where the clock-domain can be shared between the TCU logic, programming interface and PTW read channel. Does this mean that the TCU-clock has to be 'ON' for both register access and PTW, similar to above ?. So for MMU-500 clock bindings there can be a CFG_CLK (optional and not required in shared case), TBUn_CLK and TCU_CLK Regards, Sricharan >>>> differences are rather significant. I'd also note that an MMU-500 >>>> configuration may have up to *33* clocks. >>>> >>>> Either way, the QCOM implementation deserves its own compatible if only >>>> for the sake of the imp-def gaps in the architecture (e.g. FSR.SS >>>> behaviour WRT to IRQs as touched upon in the other thread). >>>> >>> >>> Ok, slightly unclear, so you mean then *clocks* are not good enough reason >>> to have a new compatible ? >> >> I beleive Robin's point was even if the clocks didn't matter, there are >> other reasons we should have the QCOM-specific compatible string. >> >> So we should have one regardless. > >Exactly. > >Robin. > >> >> Thanks, >> Mark. >> > > >_______________________________________________ >linux-arm-kernel mailing list >linux-arm-kernel@xxxxxxxxxxxxxxxxxxx >http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
