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: Tue, 23 Apr 2024 16:08:43 +0200
From: neil.armstrong@...aro.org
To: Konrad Dybcio <konrad.dybcio@...aro.org>,
 Luca Weiss <luca.weiss@...rphone.com>, 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

On 23/04/2024 15:03, Konrad Dybcio wrote:
> 
> 
> On 4/5/24 12:19, Luca Weiss wrote:
>> On Fri Apr 5, 2024 at 10:08 AM CEST, Neil Armstrong wrote:
>>> 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/
>>
>> Unfortunately I do not see any change with this on QCM6490 Fairphone 5
>> and 4-lane DP.
> 
> Hm, could you like dump all the PHY regions up and downstream with the display
> connected (and nothing connected) and compare them?

Yes would be great, PHY regions and DP regions as well.

Neil

> 
> Konrad