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

[Rajendra Nayak]

On 1/10/2023 3:12 AM, Doug Anderson wrote:
> Hi,
>
> On Mon, Jan 9, 2023 at 1:36 PM Dmitry Baryshkov
> <dmitry.baryshkov@xxxxxxxxxx> wrote:
> > On 09/01/2023 23:00, Doug Anderson wrote:
> > > Hi,
> > >
> > > On Tue, Dec 20, 2022 at 9:12 AM Dmitry Baryshkov
> > > <dmitry.baryshkov@xxxxxxxxxx> 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@xxxxxxxxxxx>
> > > > > > > > > Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> > > > > > > > > Reviewed-by: Matthias Kaehlcke <mka@xxxxxxxxxxxx>
> > > > > > > > > ---
> > > > > > > > > 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

Thanks Doug for the clarifications, I seem to have missed responding to this
once I was back from vacation,

> > > 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)?

Yes, the OPP differences are taken care of with no changes needed in kernel.
We describe a superset of *all* OPPs supported by a SoC family in DT and the
cpufreq driver then queries the firmware for supported OPPs on a given
SoC variant and ends up disabling the rest.

> 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