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

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Message-Id: <D0C42YR1270X.23P9WCWWNB8XF@fairphone.com>
Date: Fri, 05 Apr 2024 12:19:46 +0200
From: "Luca Weiss" <luca.weiss@...rphone.com>
To: <neil.armstrong@...aro.org>, "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

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.

Regards
Luca

>
> Thanks,
> Neil
>
> > 
> > Regards
> > Luca
> > 
> >>
> >> Konrad
> >