Re: [PATCH 3/8] phy: qcom: qmp-usbc: Add DP phy mode support on QCS615

[Xiangxu Yin <quic_xiangxuy@quicinc.com>]

On 12/11/2024 5:46 PM, Dmitry Baryshkov wrote:
> On Wed, Dec 11, 2024 at 08:46:16AM +0800, Xiangxu Yin wrote:
>>
>>
>> On 12/10/2024 11:09 PM, Dmitry Baryshkov wrote:
>>> On Thu, Dec 05, 2024 at 08:31:24PM +0200, Dmitry Baryshkov wrote:
>>>> On Thu, Dec 05, 2024 at 09:26:47PM +0800, Xiangxu Yin wrote:
>>>>>
>>>>>
>>>>> On 11/29/2024 10:33 PM, Dmitry Baryshkov wrote:
>>>>>> On Fri, 29 Nov 2024 at 09:59, Xiangxu Yin <quic_xiangxuy@quicinc.com> wrote:
>>>>>>>
>>>>>>> Extended DP support for QCS615 USB or DP phy. Differentiated between
>>>>>>> USBC and DP PHY using the match table’s type, dynamically generating
>>>>>>> different types of cfg and layout attributes during initialization based
>>>>>>> on this type. Static variables are stored in cfg, while parsed values
>>>>>>> are organized into the layout structure.
>>>>>>
>>>>>> We didn't have an understanding / conclusion whether
>>>>>> qcom,usb-ssphy-qmp-usb3-or-dp PHYs are actually a single device / PHY
>>>>>> or two PHYs being placed next to each other. Could you please start
>>>>>> your commit message by explaining it? Or even better, make that a part
>>>>>> of the cover letter for a new series touching just the USBC PHY
>>>>>> driver. DP changes don't have anything in common with the PHY changes,
>>>>>> so you can split the series into two.
>>>>>>
>>>>> Before implement DP extension, we have discussed with abhinav and krishna about whether use combo, usbc or separate phy.
>>>>
>>>> What is "DP extension"?
>>>>
>> I'm sorry confusion casued by my description. It's means extend DP implemnt for USBC phy driver.
>>>>>
>>>>> We identified that DP and USB share some common controls for phy_mode and orientation.
>>>>> Specifically, 'TCSR_USB3_0_DP_PHYMODE' controls who must use the lanes - USB or DP,
>>>>> while PERIPH_SS_USB0_USB3PHY_PCS_MISC_TYPEC_CTRL controls the orientation.
>>>>> It would be more efficient for a single driver to manage these controls. 
>>>>
>>>> The question is about the hardware, not about the driver.
>>>>
>>>>> Additionally, this PHY does not support Alt Mode, and the two control registers are located in separate address spaces. 
>>>>> Therefore, even though the orientation for DP on this platform is always normal and connected to the video output board, 
>>>>> we still decided to base it on the USBC extension.
>>>>
>>>> Could you please clarify, do usb3-or-dp PHYs support DP-over-USB-C? I
>>>> thought that usbc-or-dp platforms support that, but they don't
>>>> support DP+USB pin configuration. Note, the question is broader than
>>>> just QCS615, it covers the PHY type itself.
>>>>
>>>> Also, is TCSR configuration read/write or read-only? Are we supposed to
>>>> set the register from OS or are we supposed to read it and thus detemine
>>>> the PHY mode?
>>>
>>> Any updates on these two topics?
>>>
>> Still confirming detail info with HW & design team.
>> I’ll update the information that has been confirmed so far.
>> This phy support DP-over-USB-C,but it's not support alt-mode which 2 lane work for DP, other 2 lane work for USB.
>> TCSR phy mode is read/write reg and we can read for determine phy mode.
> 
> Ok, thanks for the explanation. From my point of view:
> 
> - Implement the DP PHY to be a part of the same driver. Each device
>   supported by the usbc driver should get both PHYs.
> 
> - Make sure not to break the ABI: #phy-cells = <0> should still work and
>   return USB PHY, keeping backwards compatibility. Newer devices or
>   upgraded DT for old devices should return USB PHY for <... 0> and DP
>   PHY for <... 1>.
> 
Yes, currently we have implemented like your description,
Each deivce shoud get both PHYs, DP PHY for <... 1> and USB PHY for <... 0>.
> - I'm not shure how to handle the USB and DP coexistence, especially in
>   your case of the USB-or-DP PHY.
> 
For coexistence process:

When we start implement DP part, usb driver team said only need config TCSR phy mode and orientation during switch in USB-C port.
Based on your previous comments avout SW_PWRDN, I'm confirming with the USB team whether SW_REST/SWPWRDN/START_CTRL registers might affect DP.

Anyway, even though the original SoC design supports DP or USB over Type-C，
but on QCS615 ADP AIR platform, there are only four USB-A port which works with 'qcs615-qmp-usb3-phy' driver, and no USB-C port.
DP port is mappped from usb pin to the video out sub-board.
so we are unable to verify the switching case between DP and USB devices under USB-C.

However, I'm also confirming whether anything other will affect USB and DP each other.