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

[Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>]

On Wed, Dec 11, 2024 at 08:50:02PM +0800, Xiangxu Yin wrote:
> 
> 
> 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@xxxxxxxxxxx> 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>.

Please note the backwards compatibility clause.

> > - 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.

Thanks!

> 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.

That's also fine. We will get to that point once MSM8998 / SDM660
get USB-C support (the only current blocker is the support for the
TYPEC block of the PMI8998).

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

-- 
With best wishes
Dmitry