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

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Message-ID: <iqcofcntirmlwcpyfr4yabymqfcgyrij57bibf337tmxpa73t6@npkt6wquenf6>
Date: Tue, 10 Dec 2024 17:09:21 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Xiangxu Yin <quic_xiangxuy@...cinc.com>
Cc: Rob Clark <robdclark@...il.com>, 
	Abhinav Kumar <quic_abhinavk@...cinc.com>, Sean Paul <sean@...rly.run>, 
	Marijn Suijten <marijn.suijten@...ainline.org>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
	David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, Rob Herring <robh@...nel.org>, 
	Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Kuogee Hsieh <quic_khsieh@...cinc.com>, Vinod Koul <vkoul@...nel.org>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Linus Walleij <linus.walleij@...aro.org>, 
	Bartosz Golaszewski <brgl@...ev.pl>, quic_lliu6@...cinc.com, quic_fangez@...cinc.com, 
	linux-arm-msm@...r.kernel.org, dri-devel@...ts.freedesktop.org, freedreno@...ts.freedesktop.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org, 
	linux-gpio@...r.kernel.org
Subject: Re: [PATCH 3/8] phy: qcom: qmp-usbc: Add DP phy mode support on
 QCS615

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@...cinc.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"?
> 
> > 
> > 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?

-- 
With best wishes
Dmitry