linux-kernel - Re: [PATCH v5 12/14] phy: qcom: qmp-usbc: Add QCS615 USB/DP PHY config and DP mode support

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Message-ID: <bonlc3rnfizezrobyuazv2cmyu3hqqck7tbk2g5ryln24eiwno@jxsz2rg2dyex>
Date: Tue, 23 Sep 2025 02:38:55 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Xiangxu Yin <xiangxu.yin@....qualcomm.com>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski <krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Rob Clark <robin.clark@....qualcomm.com>,
        Dmitry Baryshkov <lumag@...nel.org>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Jessica Zhang <jessica.zhang@....qualcomm.com>,
        Sean Paul <sean@...rly.run>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
        linux-arm-msm@...r.kernel.org, linux-phy@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org,
        fange.zhang@....qualcomm.com, yongxing.mou@....qualcomm.com,
        li.liu@....qualcomm.com, Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konradybcio@...nel.org>
Subject: Re: [PATCH v5 12/14] phy: qcom: qmp-usbc: Add QCS615 USB/DP PHY
 config and DP mode support

On Mon, Sep 22, 2025 at 07:28:17PM +0800, Xiangxu Yin wrote:
> 
> On 9/22/2025 5:45 PM, Dmitry Baryshkov wrote:
> > On Mon, Sep 22, 2025 at 02:58:17PM +0800, Xiangxu Yin wrote:
> >> On 9/20/2025 2:41 AM, Dmitry Baryshkov wrote:
> >>> On Fri, Sep 19, 2025 at 10:24:29PM +0800, Xiangxu Yin wrote:
> >>>> Add QCS615-specific configuration for USB/DP PHY, including DP init
> >>>> routines, voltage swing tables, and platform data. Add compatible
> >>>> "qcs615-qmp-usb3-dp-phy".
> >>>>
> >>>> Signed-off-by: Xiangxu Yin <xiangxu.yin@....qualcomm.com>
> >>>> ---
> >>>>  drivers/phy/qualcomm/phy-qcom-qmp-usbc.c | 395 +++++++++++++++++++++++++++++++
> >>>>  1 file changed, 395 insertions(+)
> >>>>
> >>>> +
> >>>> +	writel(0x3f, qmp->dp_tx + QSERDES_V2_TX_TRANSCEIVER_BIAS_EN);
> >>>> +	writel(0x10, qmp->dp_tx + QSERDES_V2_TX_HIGHZ_DRVR_EN);
> >>>> +	writel(0x0a, qmp->dp_tx + QSERDES_V2_TX_TX_POL_INV);
> >>>> +	writel(0x3f, qmp->dp_tx2 + QSERDES_V2_TX_TRANSCEIVER_BIAS_EN);
> >>>> +	writel(0x10, qmp->dp_tx2 + QSERDES_V2_TX_HIGHZ_DRVR_EN);
> >>>> +	writel(0x0a, qmp->dp_tx2 + QSERDES_V2_TX_TX_POL_INV);
> >>> Are you sure that these don't need to be adjusted based on
> >>> qmp->orientation or selected lanes count?
> >>>
> >>> In fact... I don't see orientation handling for DP at all. Don't we need
> >>> it?
> >>
> >> Thanks for the review.
> >>
> >> I agree with your reasoning and compared talos 14nm HPG with hana/kona
> >> 7nm PHY HPG; the 7nm COMBO PHY series has orientation/lane-count dependent
> >> configs, but the 14nm PHY series does not. On QCS615 (talos), the TX_*
> >> registers you pointed to are programmed with constant values regardless
> >> of orientation or lane count. This has been confirmed from both the HPG
> >> and the downstream reference driver.
> > Thanks for the confirmation.
> >
> >> For orientation, from reference the only difference is DP_PHY_MODE, which
> >> is set by qmp_usbc_configure_dp_mode(). The DP PHY does have an
> >> SW_PORTSELECT-related register, but due to talos lane mapping from the
> >> DP controller to the PHY not being the standard <0 1 2 3> sequence, it
> >> cannot reliably handle orientation flip. Also, QCS615 is a fixed-
> >> orientation platform (not DP-over-TypeC), so there is no validated hardware
> >> path for orientation flip on this platform.
> > Wait... I thought that the the non-standard lane order is handled by the
> > DP driver, then we should be able to handle the orientation inside PHY
> > driver as usual.
> 
> 
> Yes, I have confirmed this with our verification team.
> 
> For the non-standard lane order, handling flip requires swapping mapped 
> lane 0 ↔ lane 3 and lane 1 ↔ lane 2 in the logical2physical mapping.
> This is a hardware limitation, and with the current PHY driver we cannot
> propagate orientation status to dp_ctrl for processing.

This might mean that we might need to make DP host receive mux
messages...

> 
> 
> > Anyway, please add a FIXME comment into the source file and a note to
> > the commit message that SW_PORTSELECT should be handled, but it's not a
> > part of this patch for the stated reasons.
> 
> 
> OK, I will add a |FIXME| comment in |qmp_usbc_dp_power_on| and update the
> related commit message.

Thanks!

-- 
With best wishes
Dmitry