On Wed, 12 Aug 2020 at 06:06, Lyude Paul <lyude@xxxxxxxxxx> wrote:
>
> This is another bit that we never implemented for nouveau: dongle
> detection. When a "dongle", e.g. an active display adaptor, is hooked up
> to the system and causes an HPD to be fired, we don't actually know
> whether or not there's anything plugged into the dongle without checking
> the sink count. As a result, plugging in a dongle without anything
> plugged into it currently results in a bogus EDID retrieval error in the kernel log.
>
> Additionally, most dongles won't send another long HPD signal if the
> user suddenly plugs something in, they'll only send a short HPD IRQ with
> the expectation that the source will check the sink count and reprobe
> the connector if it's changed - something we don't actually do. As a
> result, nothing will happen if the user plugs the dongle in before
> plugging something into the dongle.
>
> So, let's fix this by checking the sink count in both
> nouveau_dp_probe_dpcd() and nouveau_dp_irq(), and reprobing the
> connector if things change.
>
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
Reviewed-by: Ben Skeggs <bskeggs@xxxxxxxxxx>
> ---
> drivers/gpu/drm/nouveau/nouveau_dp.c | 54 ++++++++++++++++++++---
> drivers/gpu/drm/nouveau/nouveau_encoder.h | 2 +
> 2 files changed, 51 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dp.c b/drivers/gpu/drm/nouveau/nouveau_dp.c
> index f6950a62138ca..f41fa513023fd 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dp.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dp.c
> @@ -36,12 +36,22 @@ MODULE_PARM_DESC(mst, "Enable DisplayPort multi-stream (default: enabled)");
> static int nouveau_mst = 1;
> module_param_named(mst, nouveau_mst, int, 0400);
>
> +static bool
> +nouveau_dp_has_sink_count(struct drm_connector *connector,
> + struct nouveau_encoder *outp)
> +{
> + return drm_dp_has_sink_count(connector, outp->dp.dpcd,
> + &outp->dp.desc);
> +}
> +
> static enum drm_connector_status
> nouveau_dp_probe_dpcd(struct nouveau_connector *nv_connector,
> struct nouveau_encoder *outp)
> {
> + struct drm_connector *connector = &nv_connector->base;
> struct drm_dp_aux *aux = &nv_connector->aux;
> struct nv50_mstm *mstm = NULL;
> + enum drm_connector_status status = connector_status_disconnected;
> int ret;
> u8 *dpcd = outp->dp.dpcd;
>
> @@ -50,9 +60,9 @@ nouveau_dp_probe_dpcd(struct nouveau_connector *nv_connector,
> ret = drm_dp_read_desc(aux, &outp->dp.desc,
> drm_dp_is_branch(dpcd));
> if (ret < 0)
> - return connector_status_disconnected;
> + goto out;
> } else {
> - return connector_status_disconnected;
> + goto out;
> }
>
> if (nouveau_mst) {
> @@ -61,12 +71,33 @@ nouveau_dp_probe_dpcd(struct nouveau_connector *nv_connector,
> mstm->can_mst = drm_dp_has_mst(aux, dpcd);
> }
>
> + if (nouveau_dp_has_sink_count(connector, outp)) {
> + ret = drm_dp_get_sink_count(aux);
> + if (ret < 0)
> + goto out;
> +
> + outp->dp.sink_count = ret;
> +
> + /*
> + * Dongle connected, but no display. Don't bother reading
> + * downstream port info
> + */
> + if (!outp->dp.sink_count)
> + return connector_status_disconnected;
> + }
> +
> ret = drm_dp_downstream_read_info(aux, dpcd,
> outp->dp.downstream_ports);
> if (ret < 0)
> - return connector_status_disconnected;
> + goto out;
>
> - return connector_status_connected;
> + status = connector_status_connected;
> +out:
> + if (status != connector_status_connected) {
> + /* Clear any cached info */
> + outp->dp.sink_count = 0;
> + }
> + return status;
> }
>
> int
> @@ -161,6 +192,8 @@ void nouveau_dp_irq(struct nouveau_drm *drm,
> struct drm_connector *connector = &nv_connector->base;
> struct nouveau_encoder *outp = find_encoder(connector, DCB_OUTPUT_DP);
> struct nv50_mstm *mstm;
> + int ret;
> + bool send_hpd = false;
>
> if (!outp)
> return;
> @@ -172,12 +205,23 @@ void nouveau_dp_irq(struct nouveau_drm *drm,
>
> if (mstm && mstm->is_mst) {
> if (!nv50_mstm_service(drm, nv_connector, mstm))
> - nouveau_connector_hpd(connector);
> + send_hpd = true;
> } else {
> drm_dp_cec_irq(&nv_connector->aux);
> +
> + if (nouveau_dp_has_sink_count(connector, outp)) {
> + ret = drm_dp_get_sink_count(&nv_connector->aux);
> + if (ret != outp->dp.sink_count)
> + send_hpd = true;
> + if (ret >= 0)
> + outp->dp.sink_count = ret;
> + }
> }
>
> mutex_unlock(&outp->dp.hpd_irq_lock);
> +
> + if (send_hpd)
> + nouveau_connector_hpd(connector);
> }
>
> /* TODO:
> diff --git a/drivers/gpu/drm/nouveau/nouveau_encoder.h b/drivers/gpu/drm/nouveau/nouveau_encoder.h
> index c1924a4529a7b..21937f1c7dd90 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_encoder.h
> +++ b/drivers/gpu/drm/nouveau/nouveau_encoder.h
> @@ -74,6 +74,8 @@ struct nouveau_encoder {
> u8 dpcd[DP_RECEIVER_CAP_SIZE];
> u8 downstream_ports[DP_MAX_DOWNSTREAM_PORTS];
> struct drm_dp_desc desc;
> +
> + u8 sink_count;
> } dp;
> };
>
> --
> 2.26.2
>
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