Messages in this thread | | | Subject | Re: [PATCH v4 2/2] arm64: dts: sc7180: Add required-opps for i2c | From | Rajendra Nayak <> | Date | Tue, 20 Jul 2021 09:59:09 +0530 |
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On 7/20/2021 12:49 AM, Bjorn Andersson wrote: > On Mon 19 Jul 04:37 CDT 2021, Rajendra Nayak wrote: > >> >> >> On 7/17/2021 3:29 AM, Bjorn Andersson wrote: >>> On Fri 16 Jul 16:49 CDT 2021, Stephen Boyd wrote: >>> >>>> Quoting Bjorn Andersson (2021-07-16 13:52:12) >>>>> On Fri 16 Jul 15:21 CDT 2021, Stephen Boyd wrote: >>>>> >>>>>> Quoting Bjorn Andersson (2021-07-16 13:18:56) >>>>>>> On Fri 16 Jul 05:00 CDT 2021, Rajendra Nayak wrote: >>>>>>> >>>>>>>> qup-i2c devices on sc7180 are clocked with a fixed clock (19.2 MHz) >>>>>>>> Though qup-i2c does not support DVFS, it still needs to vote for a >>>>>>>> performance state on 'CX' to satisfy the 19.2 Mhz clock frequency >>>>>>>> requirement. >>>>>>>> >>>>>>> >>>>>>> Sounds good, but... >>>>>>> >>>>>>>> Use 'required-opps' to pass this information from >>>>>>>> device tree, and also add the power-domains property to specify >>>>>>>> the CX power-domain. >>>>>>>> >>>>>>> >>>>>>> ..is the required-opps really needed with my rpmhpd patch in place? >>>>>>> >>>>>> >>>>>> Yes? Because rpmhpd_opp_low_svs is not the lowest performance state for >>>>>> CX. >>>>> >>>>> On e.g. sm8250 the first available non-zero corner presented in cmd-db >>>>> is low_svs. >> >> what rail is this? the mmcx? Perhaps it does not support RET. >> cx usually supports both collapse state and RET. >> > > That was the one I was specifically looking at for the MDSS_GDSC->MMCX > issue, so it's likely I didn't look elsewhere. > >>>> >>>> Indeed. On sc7180 it's not the first non-zero corner. I suppose >>>> retention for CX isn't actually used when the SoC is awake so your >>>> rpmhpd patch is putting in a vote for something that doesn't do anything >>>> at runtime for CX? I imagine that rpmh only sets the aggregate corner to >>>> retention when the whole SoC is suspended/sleeping, otherwise things >>>> wouldn't go very well. Similarly, min_svs may be VDD minimization? If >>>> so, those first two states are basically states that shouldn't be used >>>> at runtime, almost like sleep states. >>>> >>> >>> But if that's the case, I don't think it's appropriate for the "enabled >>> state" of the domain to use any of those corners. >> >> I rechecked the downstream kernels where all this voting happens from within >> the clock drivers, and I do see votes to min_svs for some clocks, but Stephen is >> right that RET is not something that's voted on while in active state. >> >> But always going with something just above the ret level while active will also >> not work for all devices, for instance for i2c on 7180, it needs a cx vote of >> low svs while the rail (cx) does support something lower than that which is min svs. >> (why can't it just work with min svs?, I don't know, these values and recommendations >> come in from the voltage plans published by HW teams for every SoC and we just end up >> using them in SW, perhaps something to dig further and understand which I will try and >> do but these are the values in voltage plans and downstream kernels which work for now) >> > > So to some degree this invalidates my argumentation about the > enabled_corner in rpmhpd, given that "enabled" means a different corner > for each rail - not just the one with lowest non-zero value.
Right, it might work in some cases but might not work for all.
> > So perhaps instead of introducing the enabled_corner we need to > introduce your patch and slap a WARN_ON(corner == 0) in > rpmhpd_power_on() - to ensure that all clients that uses a rpmhpd domain > actually do vote for a high enough corner?
So this would mean the expectation is that the clients set the perf state/corner before they call power_on? I don;t think that's the case today with most clients, infact its the opposite, we power on first and then make a call to set the perf state of the domain.
> > Regards, > Bjorn > >>> >>> As this means that anyone who needs any of the rpmhpd domains active >>> also needs to specify required-opps, which wouldn't be needed for any >>> other power domain provider. >>> >>> And more importantly it means that a device sitting in a GDSC, which >>> would be parented by a rpmhpd domain has no way to specify the GDSC and >>> trickle the minimum-vote up to the rpmhpd domain. (And I know that we >>> don't describe the parentship of the GDSCs today, but this patch >>> tells me that it's around the corner - for more than MMCX) >>> >>> Regards, >>> Bjorn >>> >>>>> >>>>> And if this (which?) clock requires a higher corner than the lowest >>>>> possible in order to tick at this "lowest" frequency, I'm certainly >>>>> interested in some more details. >>>>> >> >> -- >> QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member >> of Code Aurora Forum, hosted by The Linux Foundation
-- QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, hosted by The Linux Foundation
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