linux-kernel - Re: [PATCH v5 5/9] drm/bridge: anx7625: Add typec_mux

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Date:   Wed, 6 Jul 2022 11:26:19 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        bleung@...omium.org, heikki.krogerus@...ux.intel.com,
        Pin-Yen Lin <treapking@...omium.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Nícolas F . R . A . Prado 
        <nfraprado@...labora.com>, Allen Chen <allen.chen@....com.tw>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>, devicetree@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Jonas Karlman <jonas@...boo.se>,
        José Expósito <jose.exposito89@...il.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Maxime Ripard <maxime@...no.tech>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Xin Ji <xji@...logixsemi.com>
Subject: Re: [PATCH v5 5/9] drm/bridge: anx7625: Add typec_mux_set callback function

On Thu, Jun 30, 2022 at 4:38 PM Prashant Malani <pmalani@...omium.org> wrote:
>
> On Thu, Jun 30, 2022 at 4:21 PM Stephen Boyd <swboyd@...omium.org> wrote:
> >
> > Quoting Prashant Malani (2022-06-28 13:56:22)
> > > On Tue, Jun 28, 2022 at 1:40 PM Stephen Boyd <swboyd@...omium.org> wrote:
> > > >
> > > > I suppose none of those things matter though as long as there is some
> > > > typec switch registered here so that the driver can be informed of the
> > > > pin assignment. Is it right that the "mode-switch" property is only
> > > > required in DT if this device is going to control the mode of the
> > > > connector, i.e. USB+DP, or just DP? Where this device can't do that
> > > > because it doesn't support only DP.
> > >
> > > If the anx7625 is used just to route all lanes from 1 usb-c-connector (i.e
> > > the USB+DP case), a mode-switch wouldn't be of much use, since one
> > > would also route the CC lines to the built-in PD controller; so it will
> > > already have knowledge of what mode the switch is in.
> > >
> > > The mode-switch is likely only relevant for this hardware configuration(
> > > it's "DP only" in the sense that the USB pins to the SoC never go anywhere).
> > > One only has 2 SS lanes each (from each usb-c-connector).
> > >
> > > Since there is no CC-line, the anx7625 needs to know which one has DP
> > > enabled on it.
> >
> > Can the CC line be "captured" and not actually sent to the anx7625?
>
> That's what happens on Chrome OS. The cc line goes to the EC (and is "consumed"
> by the TCPM (Type C Port Manager)) and signals are then sent to the AP
> over the Host command interface to `cros-ec-typec`. The signals here being all
> the PD messages communicated between the peripheral and the port.
>
> > I imagine if that is possible, maybe the CC lines would go to some
> > micro-controller or something that did more typec management things and
> > then the anx7625 driver would need to do software control of the mode
> > and orientation control.
>
> I _guess_ that is possible (though it would seem odd to not use all the PD
> control hardware in that configuration)? If an system implements it in
> such a way
> then:
> 1. mode-switch: Can be updated to do something when num_typec_switches == 1 (
> in the mux_set function imp.l I haven't looked into what registers
> need to be configured, since we
> don't have this hardware implementation.
> 2. orientation-switch: This should be registered, and then flip the
> lanes when the port
> driver tells it the orientation is one way or another.
>
> So, if someone uses it that way, I think the driver needs only minor
> updates to support it.

Stephen, any pending concerns?
If not,I will post a v6 series with the suggested changes:
- Drop typec-switch binding; instead add a new top-level port with
end-points for each Type-C connector's switch.
- Drop it6505 patches.
- Squash anx7625 driver patches into one patch.
- Add a comment mentioning that we aren't registering the orientation-switch.