linux-kernel - Re: [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD card

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Date:   Tue, 13 Apr 2021 16:29:16 +0530
From:   sbhanu@...eaurora.org
To:     Doug Anderson <dianders@...gle.com>
Cc:     Veerabhadrarao Badiganti <vbadigan@...eaurora.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Asutosh Das <asutoshd@...eaurora.org>,
        Sahitya Tummala <stummala@...eaurora.org>,
        Ram Prakash Gupta <rampraka@...eaurora.org>,
        Sayali Lokhande <sayalil@...eaurora.org>,
        sartgarg@...eaurora.org, Rajendra Nayak <rnayak@...eaurora.org>,
        Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>,
        Sibi Sankar <sibis@...eaurora.org>, cang@...eaurora.org,
        pragalla@...eaurora.org, nitirawa@...eaurora.org,
        Linux MMC List <linux-mmc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>, Andy Gross <agross@...nel.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>
Subject: Re: [PATCH V2] arm64: dts: qcom: sc7280: Add nodes for eMMC and SD
 card

On 2021-03-29 20:26, Doug Anderson wrote:
> Hi,
> 
> On Thu, Mar 25, 2021 at 11:57 PM <sbhanu@...eaurora.org> wrote:
>> 
>> >>> +                       max-frequency = <192000000>;
>> >> Why do you need to specify this?
>> This helps to avoid lower speed modes running in high clock rate,
>> and As Veerabhadrarao Badiganti mentioned
> 
> Just to be clear, both Stephen and I agree that you should remove
> "max-frequency" here (see previous discussion). Bjorn is, of course,
> the file decision maker. However, unless he says "yeah, totally keep
> it in" I'd suggest dropping it from the next version.
> 
sure will drop in next version.
> 
>> >>> +                                       required-opps =
>> >>> <&rpmhpd_opp_low_svs>;
>> >>> +                                       opp-peak-kBps = <1200000
>> >>> 76000>;
>> >>> +                                       opp-avg-kBps = <1200000
>> >>> 50000>;
>> >> Why are the kBps numbers so vastly different than the ones on sc7180
>> >> for the same OPP point. That implies:
>> >>
>> >> a) sc7180 is wrong.
>> >>
>> >> b) This patch is wrong.
>> >>
>> >> c) The numbers are essentially random and don't really matter.
>> >>
>> >> Can you identify which of a), b), or c) is correct, or propose an
>> >> alternate explanation of the difference?
>> >>
>> 
>> We calculated bus votes values for both sc7180 and sc7280 with ICB 
>> tool,
>> above mentioned values we got for sc7280.
> 
> I don't know what an ICB tool is. Please clarify.
> 
> Also: just because a tool spits out numbers that doesn't mean it's
> correct. Presumably the tool could be wrong or incorrectly configured.
> We need to understand why these numbers are different.
> 
we checked with ICB tool team on this they conformed as Rennell & Kodiak 
are different chipsets,
we might see delta in ib/ab values due to delta in scaling factors.

> -Doug