Re: [PATCH v2 7/7] drm/bridge: anx7625: Add typec_mux_set callback function

[AngeloGioacchino Del Regno]

Il 14/06/22 18:58, Prashant Malani ha scritto:
> On Tue, Jun 14, 2022 at 2:08 AM Pin-yen Lin <treapking@xxxxxxxxxxxx> wrote:
> > Hi AngeloGioacchino,
> >
> >
> > On Tue, Jun 14, 2022 at 4:15 PM AngeloGioacchino Del Regno
> > <angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:
> > > Il 09/06/22 20:09, Prashant Malani ha scritto:
> > > > From: Pin-Yen Lin <treapking@xxxxxxxxxxxx>
> > > >
> > > > 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@xxxxxxxxxxxx>
> > > > Signed-off-by: Prashant Malani <pmalani@xxxxxxxxxxxx>
> > > > ---
> > > >
> > > > 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.

Hello Prashant,

You're completely right: I've finally seen where this is happening, so yes
we don't know, nor care at that moment, whether data->dp_connected is port0
or port1, we assign and check 'em both again, which is actually smart.

I'm sorry for the misunderstandment - and thank you for your reply.

Feel free to add my

Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>

Regards,
Angelo