linux-kernel - Re: [PATCH v4 1/2] dt-bindings: arm: qcom: Document the sc7280 CRD Pro boards

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Message-ID: <CAD=FV=U6KhJR+9q49=T3-aYppukRNmLrgvhaxP_ZtLP=VgSaDA@mail.gmail.com>
Date:   Mon, 9 Jan 2023 13:42:57 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     andersson@...nel.org, Rajendra Nayak <quic_rjendra@...cinc.com>,
        Matthias Kaehlcke <mka@...omium.org>, agross@...nel.org,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        konrad.dybcio@...aro.org, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 1/2] dt-bindings: arm: qcom: Document the sc7280 CRD
 Pro boards

Hi,

On Mon, Jan 9, 2023 at 1:36 PM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> On 09/01/2023 23:00, Doug Anderson wrote:
> > Hi,
> >
> > On Tue, Dec 20, 2022 at 9:12 AM Dmitry Baryshkov
> > <dmitry.baryshkov@...aro.org> wrote:
> >>
> >> On 20/12/2022 18:20, Rajendra Nayak wrote:
> >>>
> >>>
> >>> On 12/20/2022 8:00 PM, Matthias Kaehlcke wrote:
> >>>> On Tue, Dec 20, 2022 at 10:30:32AM +0530, Rajendra Nayak wrote:
> >>>>>
> >>>>> On 12/16/2022 7:49 PM, Matthias Kaehlcke wrote:
> >>>>>> On Fri, Dec 16, 2022 at 04:59:17PM +0530, Rajendra Nayak wrote:
> >>>>>>> Add compatibles for the Pro SKU of the sc7280 CRD boards
> >>>>>>> which come with a Pro variant of the qcard.
> >>>>>>> The Pro qcard variant has smps9 from pm8350c ganged up with
> >>>>>>> smps7 and smps8.
> >>>>>>>
> >>>>>>> Signed-off-by: Rajendra Nayak <quic_rjendra@...cinc.com>
> >>>>>>> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
> >>>>>>> Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
> >>>>>>> ---
> >>>>>>> v4 changes:
> >>>>>>> Added the zoglin-sku1536 compatible along with hoglin-sku1536.
> >>>>>>> Zoglin is same as the Hoglin variant, with the SPI Flash reduced
> >>>>>>> from 64MB to 8MB
> >>>>>>>
> >>>>>>>     Documentation/devicetree/bindings/arm/qcom.yaml | 6 ++++++
> >>>>>>>     1 file changed, 6 insertions(+)
> >>>>>>>
> >>>>>>> diff --git a/Documentation/devicetree/bindings/arm/qcom.yaml
> >>>>>>> b/Documentation/devicetree/bindings/arm/qcom.yaml
> >>>>>>> index 1b5ac6b02bc5..07771d4c91bd 100644
> >>>>>>> --- a/Documentation/devicetree/bindings/arm/qcom.yaml
> >>>>>>> +++ b/Documentation/devicetree/bindings/arm/qcom.yaml
> >>>>>>> @@ -558,6 +558,12 @@ properties:
> >>>>>>>               - const: google,hoglin
> >>>>>>>               - const: qcom,sc7280
> >>>>>>> +      - description: Qualcomm Technologies, Inc. sc7280 CRD Pro
> >>>>>>> platform (newest rev)
> >>>>>>> +        items:
> >>>>>>> +          - const: google,zoglin-sku1536
> >>>>>>> +          - const: google,hoglin-sku1536
> >>>>>>
> >>>>>> Is there actually such a thing as a 'hoglin-sku1536', i.e. the Pro
> >>>>>> qcard
> >>>>>> with 64MB of SPI flash, or do they all have 8MB of flash?
> >>>>>
> >>>>> The SPI flash is on the CRD mother-board and not on the qcards, so if
> >>>>> you replace
> >>>>> the qcards on the CRDs with 64MB flash you would need the
> >>>>> hoglin-sku1536 to
> >>>>> boot on those.
> >>>>
> >>>> With such a configuration how does the bootloader know it should pass
> >>>> the kernel
> >>>> the device tree for 'hoglin-sku1536' (pro) and not the non-pro
> >>>> variant? IIUC the
> >>>> device tree is selected based on pin strappings on the mother-board,
> >>>> not the
> >>>> qcard.
> >>>
> >>> The device tree is selected based on the pin strappings _and_ additional
> >>> logic
> >>> to dynamically identify modem/non-modem(wifi) as well as pro/non-pro
> >>> SKUs which
> >>> was added in the bootloaders.
> >>
> >> Just to clarify things, when you mention pro SKU, is it a separate SoC
> >> revision (like sc7280-pro vs bare sc7280), or is it a CRD revision (CRD
> >> Pro vs bare CRD)?
> >
> > I guess Rajendra never responded, but since I know the answer: it's a
> > different SoC revision. ...but the SoC in this case is on a daughter
> > card, so you could remove the daughter card containing the SoC and put
> > a new daughtercard on. That would have the effect of making an old CRD
> > revision have the new Pro SKU SoC.
>
> So, this is a new SoC. Is it 100% compatible with the sc7280? In other
> words: does it require any additional customizations (in OPP tables, in
> frequences, speed bins, etc)?

If I understand correctly, the OPP customizations have been accounted
for since the beginning. I believe that the GPU operating table
already has some fairly high operating points. Maybe commit
3bfef00d7671 ("arm64: dts: qcom: sc7280: Support gpu speedbin") was
for pro? Similarly, the CPU operating table also has some fairly high
operating points (probably for PRO?) and I think the higher points are
dynamically disabled for CPUs that don't support them. That's how it
was on sc7180, in any case.

...I will say it's not 100% compatible, though. Patch #2 in this
series deletes "vreg_s9c_0p676" on pro SKUs. As far as I know, that's
the only needed change, though.

-Doug