Looks good to me.

Reviewed-by: Lyude Paul <ly...@redhat.com>

On Wed, 2017-09-06 at 17:14 -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.
> 
> v2: Fix memory leak (Lyude)
> Cc: Lyude <ly...@redhat.com>
> Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
> Cc: Harry Wentland <harry.wentl...@amd.com>
> Signed-off-by: Dhinakaran Pandiyan <dhinakaran.pandi...@intel.com>
> ---
>  drivers/gpu/drm/drm_dp_mst_topology.c | 75
> +++++++++++++++++++++++++++++++++++
>  include/drm/drm_dp_mst_helper.h       |  2 +
>  2 files changed, 77 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_dp_mst_topology.c
> b/drivers/gpu/drm/drm_dp_mst_topology.c
> index 41b492f99955..9bc5049e7e59 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 +1765,40 @@ 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;
> +
> +     port = drm_dp_get_validated_port_ref(mgr, port);
> +     if (!port)
> +             return -EINVAL;
> +
> +     txmsg = kzalloc(sizeof(*txmsg), GFP_KERNEL);
> +     if (!txmsg) {
> +             drm_dp_put_port(port);
> +             return -ENOMEM;
> +     }
> +
> +     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 ret;
> +}
> +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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