Re: [PATCH 04/30] drm/bridge/tc358767: Don't register DP AUX channel until bridge is attached

From: Robert Foss <robert.foss@linaro.org>
To: Lyude Paul <lyude@redhat.com>
Cc: intel-gfx@lists.freedesktop.org,
	dri-devel <dri-devel@lists.freedesktop.org>,
	amd-gfx@lists.freedesktop.org, nouveau@lists.freedesktop.org,
	"Ville Syrjälä" <ville.syrjala@linux.intel.com>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Andrzej Hajda" <a.hajda@samsung.com>,
	"Neil Armstrong" <narmstrong@baylibre.com>,
	"Laurent Pinchart" <Laurent.pinchart@ideasonboard.com>,
	"Jonas Karlman" <jonas@kwiboo.se>,
	"Jernej Skrabec" <jernej.skrabec@siol.net>,
	"David Airlie" <airlied@linux.ie>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"open list" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 04/30] drm/bridge/tc358767: Don't register DP AUX channel until bridge is attached
Date: Fri, 19 Mar 2021 15:27:15 +0100	[thread overview]
Message-ID: <CAG3jFyuR6yH9bWzbmcZVRoyRUvu0qvEirVtxtcUmVEyVpeW_JQ@mail.gmail.com> (raw)
In-Reply-To: <20210219215326.2227596-5-lyude@redhat.com>

Hey Lyude,

This patch looks good to me.

Reviewed-by: Robert Foss <robert.foss@linaro.org>

On Fri, 19 Feb 2021 at 22:56, Lyude Paul <lyude@redhat.com> wrote:
>
> Since this is a bridge, we don't start out with a respective DRM device.
> Likewise this means we don't have a connector, which also means that we
> should be following drm_dp_aux_register()'s documentation advice and not
> call drm_dp_aux_register() until we have a matching connector. Instead,
> call drm_dp_aux_init() in tc_probe() and wait until tc_bridge_attach() to
> register our AUX channel. We also add tc_bridge_detach() to handle
> unregistering the AUX adapter once the bridge has been disconnected.
>
> Signed-off-by: Lyude Paul <lyude@redhat.com>
> ---
>  drivers/gpu/drm/bridge/tc358767.c | 20 +++++++++++++++-----
>  1 file changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/tc358767.c b/drivers/gpu/drm/bridge/tc358767.c
> index 34a3e4e9f717..da89922721ed 100644
> --- a/drivers/gpu/drm/bridge/tc358767.c
> +++ b/drivers/gpu/drm/bridge/tc358767.c
> @@ -1414,11 +1414,15 @@ static int tc_bridge_attach(struct drm_bridge *bridge,
>         if (flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)
>                 return 0;
>
> +       ret = drm_dp_aux_register(&tc->aux);
> +       if (ret < 0)
> +               return ret;
> +
>         /* Create DP/eDP connector */
>         drm_connector_helper_add(&tc->connector, &tc_connector_helper_funcs);
>         ret = drm_connector_init(drm, &tc->connector, &tc_connector_funcs, tc->bridge.type);
>         if (ret)
> -               return ret;
> +               goto aux_unregister;
>
>         /* Don't poll if don't have HPD connected */
>         if (tc->hpd_pin >= 0) {
> @@ -1438,10 +1442,19 @@ static int tc_bridge_attach(struct drm_bridge *bridge,
>         drm_connector_attach_encoder(&tc->connector, tc->bridge.encoder);
>
>         return 0;
> +aux_unregister:
> +       drm_dp_aux_unregister(&tc->aux);
> +       return ret;
> +}
> +
> +static void tc_bridge_detach(struct drm_bridge *bridge)
> +{
> +       drm_dp_aux_unregister(&bridge_to_tc(bridge)->aux);
>  }
>
>  static const struct drm_bridge_funcs tc_bridge_funcs = {
>         .attach = tc_bridge_attach,
> +       .detach = tc_bridge_detach,
>         .mode_valid = tc_mode_valid,
>         .mode_set = tc_bridge_mode_set,
>         .enable = tc_bridge_enable,
> @@ -1680,9 +1693,7 @@ static int tc_probe(struct i2c_client *client, const struct i2c_device_id *id)
>         tc->aux.name = "TC358767 AUX i2c adapter";
>         tc->aux.dev = tc->dev;
>         tc->aux.transfer = tc_aux_transfer;
> -       ret = drm_dp_aux_register(&tc->aux);
> -       if (ret)
> -               return ret;
> +       drm_dp_aux_init(&tc->aux);
>
>         tc->bridge.funcs = &tc_bridge_funcs;
>         if (tc->hpd_pin >= 0)
> @@ -1702,7 +1713,6 @@ static int tc_remove(struct i2c_client *client)
>         struct tc_data *tc = i2c_get_clientdata(client);
>
>         drm_bridge_remove(&tc->bridge);
> -       drm_dp_aux_unregister(&tc->aux);
>
>         return 0;
>  }
> --
> 2.29.2
>