Messages in this thread | | | Subject | Re: [PATCH v4 1/3] arm64: dts: qcom: sc7280: Add proxy interconnect requirements for modem | From | Sibi Sankar <> | Date | Thu, 26 May 2022 16:46:51 +0530 |
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On 5/21/22 12:37 AM, Stephen Boyd wrote: > Quoting Sibi Sankar (2022-05-20 11:08:52) >> Hey Bjorn, >> Thanks for taking time to review the series. >> >> On 5/20/22 2:05 AM, Bjorn Andersson wrote: >>> On Thu 19 May 09:47 PDT 2022, Sibi Sankar wrote: >>> >>>> Add interconnects that are required to be proxy voted upon during modem >>>> bootup on SC7280 SoCs. >>> >>> This looks reasonable, but how come the vote is only for DDR frequency? >>> What about the buses between modem and ddr? >> >> The proxy votes that are put in aren't for perf related reasons, the >> modem was getting llcc timeouts while trying to read contents from >> memory. The hw team recommended the proxy votes as the fix. > > Presumably the bootloader sets up some initial modem and ddr bus > bandwidth requests? Or the modem bootloader stage (MSA?) handles that > part?
Stephen/Bjorn, Sorry for the delay, took a while to dig this up. The modem interconnect is connected directly to gemnoc ddr. The path info from modem --> ddr is split up into modem --> llcc and llcc --> ddr (Similar to CPUs) i.e. in the end scaling of the path involves scaling of the two clocks, gemnoc and ddr. There isn't any default vote for modem --> llcc as such but it gets implicitly scaled when we vote max for llcc --> ddr path due to dependency maintained between the two clocks by rpmh.
-Sibi
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