Re: [PATCH 1/2] drm/dp/mst: Sideband message transaction to power up/down nodes

[Lyude Paul <lyude@redhat.com>]

On Tue, 2017-09-05 at 18:26 -0700, Dhinakaran Pandiyan wrote:
> The POWER_DOWN_PHY and POWER_UP_PHY sideband message transactions
> allow
> the source to reqest any node in a mst path or a whole path to be
> powered down or up. This allows drivers to target a specific sink in
> the
> MST topology, an improvement over just power managing the imediate
> downstream device. Secondly, since the request-reply protocol waits
> for an
> ACK, we can be sure that a downstream sink has enough time to respond
> to a
> power up/down request.
> 
> Cc: Lyude <lyude@redhat.com>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandiyan@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 73
> +++++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_mst_helper.h       |  2 +
>  2 files changed, 75 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 41b492f99955..a9f12708a046 100644
> --- a/drivers/gpu/drm/drm_dp_mst_topology.c
> +++ b/drivers/gpu/drm/drm_dp_mst_topology.c
> @@ -294,6 +294,12 @@ static void drm_dp_encode_sideband_req(struct
> drm_dp_sideband_msg_req_body *req,
>  		memcpy(&buf[idx], req->u.i2c_write.bytes, req-
> >u.i2c_write.num_bytes);
>  		idx += req->u.i2c_write.num_bytes;
>  		break;
> +
> +	case DP_POWER_DOWN_PHY:
> +	case DP_POWER_UP_PHY:
> +		buf[idx] = (req->u.port_num.port_number & 0xf) << 4;
> +		idx++;
> +		break;
>  	}
>  	raw->cur_len = idx;
>  }
> @@ -538,6 +544,22 @@ static bool
> drm_dp_sideband_parse_query_payload_ack(struct drm_dp_sideband_msg_r
>  	return false;
>  }
>  
> +
> +static bool drm_dp_sideband_parse_power_updown_phy_ack(struct
> drm_dp_sideband_msg_rx *raw,
> +						       struct
> drm_dp_sideband_msg_reply_body *repmsg)
> +{
> +	int idx = 1;
> +
> +	repmsg->u.port_number.port_number = (raw->msg[idx] >> 4) &
> 0xf;
> +	idx++;
> +	if (idx > raw->curlen) {
> +		DRM_DEBUG_KMS("power up/down phy parse length fail
> %d %d\n",
> +			      idx, raw->curlen);
> +		return false;
> +	}
> +	return true;
> +}
> +
>  static bool drm_dp_sideband_parse_reply(struct
> drm_dp_sideband_msg_rx *raw,
>  					struct
> drm_dp_sideband_msg_reply_body *msg)
>  {
> @@ -567,6 +589,9 @@ static bool drm_dp_sideband_parse_reply(struct
> drm_dp_sideband_msg_rx *raw,
>  		return
> drm_dp_sideband_parse_enum_path_resources_ack(raw, msg);
>  	case DP_ALLOCATE_PAYLOAD:
>  		return
> drm_dp_sideband_parse_allocate_payload_ack(raw, msg);
> +	case DP_POWER_DOWN_PHY:
> +	case DP_POWER_UP_PHY:
> +		return
> drm_dp_sideband_parse_power_updown_phy_ack(raw, msg);
>  	default:
>  		DRM_ERROR("Got unknown reply 0x%02x\n", msg-
> >req_type);
>  		return false;
> @@ -693,6 +718,22 @@ static int build_allocate_payload(struct
> drm_dp_sideband_msg_tx *msg, int port_n
>  	return 0;
>  }
>  
> +static int build_power_updown_phy(struct drm_dp_sideband_msg_tx
> *msg,
> +				  int port_num, bool power_up)
> +{
> +	struct drm_dp_sideband_msg_req_body req;
> +
> +	if (power_up)
> +		req.req_type = DP_POWER_UP_PHY;
> +	else
> +		req.req_type = DP_POWER_DOWN_PHY;
> +
> +	req.u.port_num.port_number = port_num;
> +	drm_dp_encode_sideband_req(&req, msg);
> +	msg->path_msg = true;
> +	return 0;
> +}
> +
>  static int drm_dp_mst_assign_payload_id(struct
> drm_dp_mst_topology_mgr *mgr,
>  					struct drm_dp_vcpi *vcpi)
>  {
> @@ -1724,6 +1765,38 @@ static int drm_dp_payload_send_msg(struct
> drm_dp_mst_topology_mgr *mgr,
>  	return ret;
>  }
>  
> +int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr
> *mgr,
> +				 struct drm_dp_mst_port *port, bool
> power_up)
> +{
> +	struct drm_dp_sideband_msg_tx *txmsg;
> +	int len, ret;
> +
> +	txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
> +	if (!txmsg)
> +		return -ENOMEM;
> +
> +	port = drm_dp_get_validated_port_ref(mgr, port);
> +	if (!port)
> +		return -EINVAL;
if (!port), then you leak memory by not freeing txmsg
> +
> +	txmsg->dst = port->parent;
> +	len = build_power_updown_phy(txmsg, port->port_num,
> power_up);
> +	drm_dp_queue_down_tx(mgr, txmsg);
> +
> +	ret = drm_dp_mst_wait_tx_reply(port->parent, txmsg);
> +	if (ret > 0) {
> +		if (txmsg->reply.reply_type == 1)
> +			ret = -EINVAL;
> +		else
> +			ret = 0;
> +	}
> +	kfree(txmsg);
> +	drm_dp_put_port(port);
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL(drm_dp_send_power_updown_phy);
> +
>  static int drm_dp_create_payload_step1(struct
> drm_dp_mst_topology_mgr *mgr,
>  				       int id,
>  				       struct drm_dp_payload
> *payload)
> diff --git a/include/drm/drm_dp_mst_helper.h
> b/include/drm/drm_dp_mst_helper.h
> index d55abb75f29a..7f78d26a0766 100644
> --- a/include/drm/drm_dp_mst_helper.h
> +++ b/include/drm/drm_dp_mst_helper.h
> @@ -631,5 +631,7 @@ int drm_dp_atomic_find_vcpi_slots(struct
> drm_atomic_state *state,
>  int drm_dp_atomic_release_vcpi_slots(struct drm_atomic_state *state,
>  				     struct drm_dp_mst_topology_mgr
> *mgr,
>  				     int slots);
> +int drm_dp_send_power_updown_phy(struct drm_dp_mst_topology_mgr
> *mgr,
> +				 struct drm_dp_mst_port *port, bool
> power_up);
>  
>  #endif
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