linux-kernel - Re: [PATCH v2 7/7] drm/bridge: anx7625: Add typec_mux

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <CACeCKafeJ40y2LYsEm4Z2pRMxzM6W+VcC1F95oFqNq+xokPWUQ@mail.gmail.com>
Date:   Tue, 14 Jun 2022 09:58:59 -0700
From:   Prashant Malani <pmalani@...omium.org>
To:     Pin-yen Lin <treapking@...omium.org>
Cc:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
        heikki.krogerus@...ux.intel.com,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        David Airlie <airlied@...ux.ie>,
        "open list:DRM DRIVERS" <dri-devel@...ts.freedesktop.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Sam Ravnborg <sam@...nborg.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Tzung-Bi Shih <tzungbi@...gle.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Nícolas F. R. A. Prado 
        <nfraprado@...labora.com>, Jonas Karlman <jonas@...boo.se>,
        swboyd@...omium.org, Rob Herring <robh+dt@...nel.org>,
        Maxime Ripard <maxime@...no.tech>,
        Hsin-Yi Wang <hsinyi@...omium.org>,
        Xin Ji <xji@...logixsemi.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Robert Foss <robert.foss@...aro.org>,
        José Expósito <jose.exposito89@...il.com>
Subject: Re: [PATCH v2 7/7] drm/bridge: anx7625: Add typec_mux_set callback function

On Tue, Jun 14, 2022 at 2:08 AM Pin-yen Lin <treapking@...omium.org> wrote:
>
> Hi AngeloGioacchino,
>
>
> On Tue, Jun 14, 2022 at 4:15 PM AngeloGioacchino Del Regno
> <angelogioacchino.delregno@...labora.com> wrote:
> >
> > Il 09/06/22 20:09, Prashant Malani ha scritto:
> > > From: Pin-Yen Lin <treapking@...omium.org>
> > >
> > > Add the callback function when the driver receives state
> > > changes of the Type-C port. The callback function configures the
> > > crosspoint switch of the anx7625 bridge chip, which can change the
> > > output pins of the signals according to the port state.
> > >
> > > Signed-off-by: Pin-Yen Lin <treapking@...omium.org>
> > > Signed-off-by: Prashant Malani <pmalani@...omium.org>
> > > ---
> > >
> > > Changes since v2:
> > > - No changes.
> > >
> > >   drivers/gpu/drm/bridge/analogix/anx7625.c | 58 +++++++++++++++++++++++
> > >   drivers/gpu/drm/bridge/analogix/anx7625.h | 13 +++++
> > >   2 files changed, 71 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/bridge/analogix/anx7625.c b/drivers/gpu/drm/bridge/analogix/anx7625.c
> > > index d41a21103bd3..2c308d12fab2 100644
> > > --- a/drivers/gpu/drm/bridge/analogix/anx7625.c
> > > +++ b/drivers/gpu/drm/bridge/analogix/anx7625.c
> > > @@ -15,6 +15,7 @@
> > >   #include <linux/regulator/consumer.h>
> > >   #include <linux/slab.h>
> > >   #include <linux/types.h>
> > > +#include <linux/usb/typec_dp.h>
> > >   #include <linux/usb/typec_mux.h>
> > >   #include <linux/workqueue.h>
> > >
> > > @@ -2582,9 +2583,66 @@ static void anx7625_runtime_disable(void *data)
> > >       pm_runtime_disable(data);
> > >   }
> > >
> > > +static void anx7625_set_crosspoint_switch(struct anx7625_data *ctx,
> > > +                                       enum typec_orientation orientation)
> > > +{
> > > +     if (orientation == TYPEC_ORIENTATION_NORMAL) {
> > > +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_0,
> > > +                               SW_SEL1_SSRX_RX1 | SW_SEL1_DPTX0_RX2);
> > > +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_1,
> > > +                               SW_SEL2_SSTX_TX1 | SW_SEL2_DPTX1_TX2);
> > > +     } else if (orientation == TYPEC_ORIENTATION_REVERSE) {
> > > +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_0,
> > > +                               SW_SEL1_SSRX_RX2 | SW_SEL1_DPTX0_RX1);
> > > +             anx7625_reg_write(ctx, ctx->i2c.tcpc_client, TCPC_SWITCH_1,
> > > +                               SW_SEL2_SSTX_TX2 | SW_SEL2_DPTX1_TX1);
> > > +     }
> > > +}
> > > +
> > > +static void anx7625_typec_two_ports_update(struct anx7625_data *ctx)
> > > +{
> > > +     if (ctx->typec_ports[0].dp_connected && ctx->typec_ports[1].dp_connected)
> > > +             /* Both ports available, do nothing to retain the current one. */
> > > +             return;
> > > +     else if (ctx->typec_ports[0].dp_connected)
> > > +             anx7625_set_crosspoint_switch(ctx, TYPEC_ORIENTATION_NORMAL);
> > > +     else if (ctx->typec_ports[1].dp_connected)
> > > +             anx7625_set_crosspoint_switch(ctx, TYPEC_ORIENTATION_REVERSE);
> > > +}
> > > +
> > >   static int anx7625_typec_mux_set(struct typec_mux_dev *mux,
> > >                                struct typec_mux_state *state)
> > >   {
> > > +     struct anx7625_port_data *data = typec_mux_get_drvdata(mux);
> > > +     struct anx7625_data *ctx = data->ctx;
> > > +     struct device *dev = &ctx->client->dev;
> > > +
> > > +     bool old_dp_connected = (ctx->typec_ports[0].dp_connected ||
> > > +                              ctx->typec_ports[1].dp_connected);
> >
> > So the old connection state is "either port0 or port1 are currently connected"...
> >
> > > +     bool new_dp_connected;
> > > +
> > > +     if (ctx->num_typec_switches == 1)
> > > +             return 0;
> > > +
> > > +     dev_dbg(dev, "mux_set dp_connected: c0=%d, c1=%d\n",
> > > +             ctx->typec_ports[0].dp_connected, ctx->typec_ports[1].dp_connected);
> > > +
> > > +     data->dp_connected = (state->alt && state->alt->svid == USB_TYPEC_DP_SID &&
> > > +                           state->alt->mode == USB_TYPEC_DP_MODE);
> > > + > + new_dp_connected = (ctx->typec_ports[0].dp_connected ||
> > > +                         ctx->typec_ports[1].dp_connected);
> >
> > ...and the new connection state is the same as the old one, because I don't see
> > anything that could ever modify it in this function's flow, until reaching this
> > assignment.
>
> The typec mux driver data (`struct anx7625_port_data *data =
> typec_mux_get_drvdata(mux)`) is set to one of the
> `ctx->typec_ports[*]` in `anx7625_register_mode_switch` (see patch 6
> of this series).
>
> So, the `data->dp_connected = ...` assignment may change the new
> connection state.

Angelo, I think your interpretation of this logic is not accurate..
|old_dp_connected| represents *whether* port1 or port0 has a DP
partner connected, not that *either* of them has it.

So, this logic looks OK to me.


>
> Best regards,
> Pin-yen
>
> >
> > > +
> > > +     /* dp on, power on first */
> > > +     if (!old_dp_connected && new_dp_connected)
> > > +             pm_runtime_get_sync(dev);
> >
> > ...so that will never happen...
> >
> > > +
> > > +     anx7625_typec_two_ports_update(ctx);
> > > +
> > > +     /* dp off, power off last */
> > > +     if (old_dp_connected && !new_dp_connected)
> > > +             pm_runtime_put_sync(dev);
> >
> > ...and same here.
> >
> > Regards,
> > Angelo