linux-kernel - Re: [PATCH 14/22] platform/chrome: cros_typec_switch: Add support for signaling HPD to drm

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Message-ID: <CAA8EJpp7NW0nT5vWdZcQ+A9GjreO9b20wfFBBnOZe6E6GcTNYg@mail.gmail.com>
Date: Sun, 11 Feb 2024 11:00:28 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Stephen Boyd <swboyd@...omium.org>
Cc: chrome-platform@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	patches@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
	devicetree@...r.kernel.org, linux-arm-msm@...r.kernel.org, 
	Douglas Anderson <dianders@...omium.org>, Pin-yen Lin <treapking@...omium.org>, 
	Prashant Malani <pmalani@...omium.org>, Benson Leung <bleung@...omium.org>, 
	Tzung-Bi Shih <tzungbi@...nel.org>
Subject: Re: [PATCH 14/22] platform/chrome: cros_typec_switch: Add support for
 signaling HPD to drm_bridge

On Sun, 11 Feb 2024 at 10:52, Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Dmitry Baryshkov (2024-02-10 06:10:31)
> > On Sat, 10 Feb 2024 at 09:14, Stephen Boyd <swboyd@...omium.org> wrote:
> > > diff --git a/drivers/platform/chrome/cros_typec_switch.c b/drivers/platform/chrome/cros_typec_switch.c
> > > index 769de2889f2f..d8fb6662cf8d 100644
> > > --- a/drivers/platform/chrome/cros_typec_switch.c
> > > +++ b/drivers/platform/chrome/cros_typec_switch.c
> > > @@ -18,6 +19,15 @@
> > >  #include <linux/usb/typec_mux.h>
> > >  #include <linux/usb/typec_retimer.h>
> > >
> > > +#include <drm/drm_bridge.h>
> > > +#include <drm/drm_print.h>
> > > +
> > > +struct cros_typec_dp_bridge {
> > > +       struct cros_typec_switch_data *sdata;
> > > +       bool hpd_enabled;
> > > +       struct drm_bridge bridge;
> > > +};
> >
> > Is there any chance that you can use drm_dp_hpd_bridge_register() /
> > drm_aux_hpd_bridge_notify() instead of implementing another
> > drm_bridge?
> > If something is missing from the existing implementation we can
> > probably work that out.
>
> Yeah I think that can work. I had put the drm_bridge in this driver
> because I needed a 'struct device' per DP phy, but I think that problem
> goes away with an auxiliary device, so that is nicely solved.
>
> I'll have to add logic about typec ports to that auxiliary driver
> though, like mapping data-lanes and handling lane assignments. And then
> I'll move this code from the cros_typec_switch driver to the
> cros_ec_typec driver so it can be called outside of the typec mux set
> path. That's probably better because it's sort of bolted on to the
> cros_typec_switch driver. We'll need to know if the DP phy needs to
> handle orientation or if the EC is doing that somehow, so probably I'll
> need to add a DT property to the google,cros-ec-typec binding to
> indicate that orientation control is needed.

I still haven't fully got into your usage of data-lanes. I hope to be
able to comment on that part and on the ports / endpoints tomorrow.

>
> It looks like I should add a new auxiliary device, like
> 'dp_typec_bridge', and have some other function like
> drm_dp_typec_bridge_register() for that. I can wrap the 'struct
> drm_aux_hpd_bridge_data' with a 'struct drm_aux_typec_bridge_data' and
> then the typec port information can live there. HPD can still be
> signaled with drm_aux_hpd_bridge_notify() but other functions can be
> used to set the active typec port, e.g.
> drm_aux_typec_bridge_set_active_port(), and then get orientation with
> typec_get_orientation() in the atomic_check().



-- 
With best wishes
Dmitry