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: <83e8c8b6-fd2c-41f5-8732-703d47764d0f@oss.qualcomm.com>
Date: Tue, 23 Sep 2025 11:48:31 +0800
From: Xiangxu Yin <xiangxu.yin@....qualcomm.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....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 9/23/2025 7:38 AM, Dmitry Baryshkov wrote:
> 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...


Yeah, downstream handles this by passing orientation and lane_cnt info via the
DP_PHY_SPARE0 PHY register. But even with that approach, dp_ctrl would still 
need access PHY address area.

Let's see if there’s any follow-up on extending this in the future.


>>
>>> 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!
>