linux-kernel - Re: [PATCH v2 0/2] usb: typec: Add new driver for Parade PS8830 Type-C Retimer

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Message-ID: <Zw5oOUeN/v+tz+SY@linaro.org>
Date: Tue, 15 Oct 2024 16:03:53 +0300
From: Abel Vesa <abel.vesa@...aro.org>
To: Johan Hovold <johan@...nel.org>
Cc: Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, linux-arm-msm@...r.kernel.org,
	Bjorn Andersson <andersson@...nel.org>,
	Konrad Dybcio <konradybcio@...nel.org>,
	Rajendra Nayak <quic_rjendra@...cinc.com>,
	Sibi Sankar <quic_sibis@...cinc.com>,
	Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
	Trilok Soni <quic_tsoni@...cinc.com>, linux-kernel@...r.kernel.org,
	linux-usb@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 0/2] usb: typec: Add new driver for Parade PS8830
 Type-C Retimer

On 24-10-15 14:41:25, Johan Hovold wrote:
> On Fri, Oct 04, 2024 at 04:57:36PM +0300, Abel Vesa wrote:
> > The Parade PS8830 is a Type-C multi-protocol retimer that is controlled
> > via I2C. It provides altmode and orientation handling and usually sits
> > between the Type-C port and the PHY.
> > 
> > It is currently used alongside Qualcomm Snapdragon X Elite SoCs on quite
> > a few laptops already.
> > 
> > This new driver adds support for the following 3 modes:
> >  - DP 4lanes (pin assignments C and E)
> >  - DP 2lanes + USB3 (pin assignment D)
> >  - USB3
> > 
> > This retimer is a LTTPR (Link-Training Tunable PHY Repeater) which means
> > it can support link training from source to itself. This means that the
> > DP driver needs to be aware of the repeater presence and to handle
> > the link training accordingly. This is currently missing from msm dp
> > driver, but there is already effort going on to add it. Once done,
> > full external DP will be working on all X1E laptops that make use of
> > this retimer.
> 
> I was gonna ask you to include the devicetree changes that enables the
> retimers as part of this series (to facilitate review and testing), but
> perhaps you should indeed not post them again until LTTPR support is in
> place.

I was thinking maybe we should not wait for LTTPR support as this series
brings orientation support as is. I still need to figure out how to
strip out the DP parts of it in such a way that orientation should still
be working but DP should not (until LTTPR is in).

> 
> > Signed-off-by: Abel Vesa <abel.vesa@...aro.org>
> > ---
> > Changes in v2:
> > - Addressed all comments from Johan and Konrad.
> > - Reworked the handling of the vregs so it would be more cleaner.
> >   Dropped the usage of bulk regulators API and handled them separately.
> >   Also discribed all regulators according to data sheet.
> > - Added all delays according to data sheet.
> > - Fixed coldplug (on boot) orientation detection.
> 
> Coldplug orientation detection still does not work here with this series
> applied.
> 
> I'm not entirely sure this whether worked better with v1, but with v2
> my SuperSpeed ethernet device shows up as a HighSpeed device in one
> orientation. It is also not disconnected an re-enumerated as SS as is
> the case on the X13s (and possibly with v1):
> 
> 	usb 1-1: new high-speed USB device number 2 using xhci-hcd

For coldplug, this series does the right thing as it leaves the retimer
initialized if it was left enabled at boot. There is a second part
needed for the coldplug to work. That is the regulator-boot-on property
in retimer's vregs nodes. That will ensure that the regulator is not
disabled until retimer driver probes and will keep the retimer initialized
until USB device is enumerated.

> 
> > - Didn't pick Krzysztof's R-b tag because the bindings changed w.r.t
> >   supplies.
> > - Link to v1: https://lore.kernel.org/r/20240829-x1e80100-ps8830-v1-0-bcc4790b1d45@linaro.org
> > 
> > ---
> > Abel Vesa (2):
> >       dt-bindings: usb: Add Parade PS8830 Type-C retimer bindings
> >       usb: typec: Add support for Parade PS8830 Type-C Retimer
> 
> Johan