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

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Message-ID: <2ed80ba6-e64f-4122-a6bc-c224c4e92e0f@gmail.com>
Date: Tue, 15 Oct 2024 21:10:12 +0200
From: Konrad Dybcio <konradybcio@...il.com>
To: Abel Vesa <abel.vesa@...aro.org>, 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 10/15/24 15:03, Abel Vesa wrote:
> 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.

It also happens to bring an undesired crash-on-unplug feature when
DP is enabled.. I suppose it's fine to bring this series in if you
separate enabling the retimer on devices from wiring DP up.

Konrad