Re: [PATCH v2 2/4] dt-bindings: phy: qcom,msm8998-qmp-usb3-phy: Add support for Shikra

[Dmitry Baryshkov]

On Fri, May 15, 2026 at 09:06:21PM +0530, Krishna Kurapati wrote:
> 
> 
> On 5/14/2026 8:07 PM, Krzysztof Kozlowski wrote:
> > On 14/05/2026 08:22, Krishna Kurapati wrote:
> > > 
> > > 
> > > On 5/14/2026 12:26 AM, Krzysztof Kozlowski wrote:
> > > > On 07/05/2026 13:37, Krishna Kurapati wrote:
> > > > > 
> > > > > 
> > > > > On 5/5/2026 7:30 PM, Krzysztof Kozlowski wrote:
> > > > > > On 05/05/2026 15:57, Krishna Kurapati wrote:
> > > > > > > 
> > > > > > > 
> > > > > > > On 5/5/2026 6:59 PM, Krzysztof Kozlowski wrote:
> > > > > > > > On 05/05/2026 15:27, Krishna Kurapati wrote:
> > > > > > > > > 
> > > > > > > > > 
> > > > > > > > > On 5/5/2026 4:22 PM, Krzysztof Kozlowski wrote:
> > > > > > > > > > On 05/05/2026 12:49, Krzysztof Kozlowski wrote:
> > > > > > > > > > > On Mon, May 04, 2026 at 10:36:57PM +0530, Krishna Kurapati wrote:
> > > > > > > > > > > > Declare the USB-C QMP PHY present on the Qualcomm Shikra platform.
> > > > > > > > > > > > 
> > > > > > > > > > > > Signed-off-by: Krishna Kurapati <krishna.kurapati@xxxxxxxxxxxxxxxx>
> > > > > > > > > > > > ---
> > > > > > > > > > > >       .../devicetree/bindings/phy/qcom,msm8998-qmp-usb3-phy.yaml      | 2 ++
> > > > > > > > > > > >       1 file changed, 2 insertions(+)
> > > > > > > > > > > 
> > > > > > > > > > > Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxxxxxxxx>
> > > > > > > > > > 
> > > > > > > > > > ... and then I looked at the driver. So un-reviewed. Devices are clearly
> > > > > > > > > > compatible. If not, explain what is not compatible.
> > > > > > > > > > 
> > > > > > > > > Talos uses GCC_USB3_PRIM_PHY_AUX_CLK.
> > > > > > > > > 
> > > > > > > > > In Shikra, we are using GCC_USB3_PRIM_PHY_COM_AUX_CLK. We don't have
> > > > > > > > > GCC_USB3_PRIM_PHY_AUX_CLK.
> > > > > > > > > 
> > > > > > > > > Hence, I didn't use a fallback compatible.
> > > > > > > > 
> > > > > > > > This still explains nothing. How different clock makes interface for SW
> > > > > > > > incompatible exactly?
> > > > > > > > 
> > > > > > > So I went by the naming. AUX vs COM_AUX.
> > > > > > 
> > > > > > The naming does not matter. If the clock is called
> > > > > > "no_one_expects_spanish_inquisition", does that make software
> > > > > > incompatible? Why would the name itself matter?
> > > > > > 
> > > > > > > 
> > > > > > > Can I use a fallback compatible and in DT vote for "COM_AUX" clock with
> > > > > > > clock-names mentioning "aux" ?
> > > > > > 
> > > > > > I don't know, I asked what is different in software interface.
> > > > > > 
> > > > > 
> > > > > Hi Krzysztof,
> > > > > 
> > > > >     I checked with the hw team here and found out two things.
> > > > > 
> > > > >     1. Shikra is a spinoff of Agatti and its sw interface (clocks used and
> > > > > regulators used) is the same as agatti.
> > > > > 
> > > > >     2. I thought we could use qcm2290 as a fallback since the phy register
> > > > > init sequence is the same for Talos/Shikra/Agatti. The difference
> > > > > between Talos and agatti when checked in the driver was the init load
> > > > > settings. I checked with the hw team and they suggested using the init
> > > > > load settings which talos was using.
> > > > > 
> > > > >     Hence both these compatibles (qcm2290 and qcs615) cannot be used as
> > > > > fallback for Shikra.
> > > > 
> > > > Then I do not understand why you are using qcs615_usb3phy_cfg for
> > > > Shikra. You say that the initialization is different, but you use
> > > > exactly the same initialization. So in a meaning of compatibility
> > > > between hardware for Devicetree they are compatible.
> > > > 
> > > Hi Krzysztof,
> > > 
> > >    There are 3 things:
> > > 
> > > 1. Clocks used:
> > > -> Talos supports AUX Clock since it supports DP over USB.
> > > -> Agatti and Shikra use COM_AUX clock since they dont support DP over USB.
> > > 
> > > 2. Phy register Init sequence - same for all 3 targets
> > > 
> > > 3. Regulator init load:
> > > -> Different for both Talos and Agatti
> > > -> Recommendation is to use Talos regulator load values.
> > > 
> > > SW interface wise, shikra is comaptible with agatti. If we use agatti as
> > > fallback, we would end up using the platform data of Agatti where the
> > > regulator init load is not suitable for Shikra. Hence not using Agatti
> > > as fallback.
> > > 
> > > Coming to driver changes, I used qcs615_cfg because it has required phy
> > > register sequence and regulator init load as needed by shikra.
> > 
> > So is it compatible with QCS615? If not, then something is incomplete or
> > confusing. The driver uses the same software interface.
> > 
> Sorry for the confusion. The Talos compatible represents the USB/DP PHY with
> aux clock input, while Shikra is a USB-only PHY with com_aux input clock, so
> the two PHYs are not compatible with each other.

According to the memory map, there is an (unused) DP registers part
right after the QMP USB3 PHY. So, sofware-wise it is compatible to
Talos. Having the different clock input means different integration of
the block rather than the differences in the hardware block.

So, the block should be compatible to qcom,qcs615-qmp-usb3-dp-phy

> 
> In the Linux driver implementation the match data is currently used only to
> affect the init sequence and regulator init load and here Shikra can reuse
> the Talos match data structure.
> 
> Regards,
> Krishna,
> 
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-- 
With best wishes
Dmitry