linux-kernel - Re: [PATCH RFT 0/7] arm64: qcom: allow up to 4 lanes for the Type-C DisplayPort Altmode

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Date: Fri, 5 Apr 2024 10:08:34 +0200
From: Neil Armstrong <neil.armstrong@...aro.org>
To: Luca Weiss <luca.weiss@...rphone.com>,
 Konrad Dybcio <konrad.dybcio@...aro.org>,
 Bjorn Andersson <andersson@...nel.org>
Cc: Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I
 <kishon@...nel.org>, Rob Herring <robh@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Abhinav Kumar
 <quic_abhinavk@...cinc.com>, linux-arm-msm@...r.kernel.org,
 linux-phy@...ts.infradead.org, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFT 0/7] arm64: qcom: allow up to 4 lanes for the Type-C
 DisplayPort Altmode

Hi Luca,

On 29/03/2024 10:02, Luca Weiss wrote:
> On Tue Mar 26, 2024 at 10:02 PM CET, Konrad Dybcio wrote:
>> On 16.03.2024 5:01 PM, Bjorn Andersson wrote:
>>> On Fri, Mar 15, 2024 at 06:35:15PM +0100, Neil Armstrong wrote:
>>>> On 15/03/2024 18:19, Luca Weiss wrote:
>>>>> On Thu Feb 29, 2024 at 2:07 PM CET, Neil Armstrong wrote:
>>>>>> Register a typec mux in order to change the PHY mode on the Type-C
>>>>>> mux events depending on the mode and the svid when in Altmode setup.
>>>>>>
>>>>>> The DisplayPort phy should be left enabled if is still powered on
>>>>>> by the DRM DisplayPort controller, so bail out until the DisplayPort
>>>>>> PHY is not powered off.
>>>>>>
>>>>>> The Type-C Mode/SVID only changes on plug/unplug, and USB SAFE states
>>>>>> will be set in between of USB-Only, Combo and DisplayPort Only so
>>>>>> this will leave enough time to the DRM DisplayPort controller to
>>>>>> turn of the DisplayPort PHY.
>>>>>>
>>>>>> The patchset also includes bindings changes and DT changes.
>>>>>>
>>>>>> This has been successfully tested on an SM8550 board, but the
>>>>>> Thinkpad X13s deserved testing between non-PD USB, non-PD DisplayPort,
>>>>>> PD USB Hubs and PD Altmode Dongles to make sure the switch works
>>>>>> as expected.
>>>>>>
>>>>>> The DisplayPort 4 lanes setup can be check with:
>>>>>> $ cat /sys/kernel/debug/dri/ae01000.display-controller/DP-1/dp_debug
>>>>>> 	name = msm_dp
>>>>>> 	drm_dp_link
>>>>>> 		rate = 540000
>>>>>> 		num_lanes = 4
>>>>>
>>>>> Hi Neil,
>>>>>
>>>>> I tried this on QCM6490/SC7280 which should also support 4-lane DP but I
>>>>> haven't had any success so far.
>>>>>
>>> [..]
>>>>> [ 1775.563969] [drm:dp_ctrl_link_train] *ERROR* max v_level reached
>>>>> [ 1775.564031] [drm:dp_ctrl_link_train] *ERROR* link training #1 failed. ret=-11
>>>>
>>>> Interesting #1 means the 4 lanes are not physically connected to the other side,
>>>> perhaps QCM6490/SC7280 requires a specific way to enable the 4 lanes in the PHY,
>>>> or some fixups in the init tables.
>>>>
>>>
>>> I tested the same on rb3gen2 (qcs6490) a couple of weeks ago, with the
>>> same outcome. Looking at the AUX reads, after switching to 4-lane the
>>> link training is failing on all 4 lanes, in contrast to succeeding only
>>> on the first 2 if you e.g. forget to mux the other two.
>>>
>>> As such, my expectation is that there's something wrong in the QMP PHY
>>> (or possibly redriver) for this platform.
>>
>> Do we have any downstream tag where 4lane dp works? I'm willing to believe
>> the PHY story..
> 
> Just tested on Fairphone 5 downstream and 4 lane appears to work there.
> This is with an USB-C to HDMI adapter that only does HDMI.
> 
> FP5:/ # cat /sys/kernel/debug/drm_dp/dp_debug
>          state=0x20a5
>          link_rate=270000
>          num_lanes=4
>          resolution=2560x1440@...z
>          pclock=241500KHz
>          bpp=24
>          test_req=DP_LINK_STATUS_UPDATED
>          lane_count=4
>          bw_code=10
>          v_level=0
>          p_level=0
> 
> Sources are here:
> https://gerrit-public.fairphone.software/plugins/gitiles/kernel/msm-5.4/+/refs/heads/odm/rc/target/13/fp5
> And probably more importantly techpack/display:
> https://gerrit-public.fairphone.software/plugins/gitiles/platform/vendor/opensource/display-drivers/+/refs/heads/odm/rc/target/13/fp5
> Dts if useful:
> https://gerrit-public.fairphone.software/plugins/gitiles/kernel/msm-extra/devicetree/+/refs/heads/kernel/13/fp5

Could you retry with this applied ?

https://lore.kernel.org/all/20240405000111.1450598-1-swboyd@chromium.org/

Thanks,
Neil

> 
> Regards
> Luca
> 
>>
>> Konrad
>