mlxsw: core_linecards: Expose device PSID over device info

Use tunneled MGIR to obtain PSID of line card device and extend
device_info_get() op to fill up the info with that.

Example:

$ devlink dev info auxiliary/mlxsw_core.lc.0
auxiliary/mlxsw_core.lc.0:
versions:
fixed:
hw.revision 0
fw.psid MT_0000000749
running:
ini.version 4
fw 19.2010.1312

Signed-off-by: Jiri Pirko <[e-mail]>
Reviewed-by: Ido Schimmel <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/networking/devlink/mlxsw.rst

···
    * - ``ini.version``
      - running
      - Version of line card INI loaded
+   * - ``fw.psid``
+     - fixed
+     - Line card device PSID
    * - ``fw.version``
      - running
      - Three digit firmware version of line card device

drivers/net/ethernet/mellanox/mlxsw/core.h

···
 	u16 fw_major;
 	u16 fw_minor;
 	u16 fw_sub_minor;
+	char psid[MLXSW_REG_MGIR_FW_INFO_PSID_SIZE];
 };
 
 struct mlxsw_linecard {

drivers/net/ethernet/mellanox/mlxsw/core_linecards.c

···
 	return linecard->name;
 }
 
+static int mlxsw_linecard_device_psid_get(struct mlxsw_linecard *linecard,
+					  u8 device_index, char *psid)
+{
+	struct mlxsw_core *mlxsw_core = linecard->linecards->mlxsw_core;
+	char mddt_pl[MLXSW_REG_MDDT_LEN];
+	char *mgir_pl;
+	int err;
+
+	mlxsw_reg_mddt_pack(mddt_pl, linecard->slot_index, device_index,
+			    MLXSW_REG_MDDT_METHOD_QUERY,
+			    MLXSW_REG(mgir), &mgir_pl);
+
+	mlxsw_reg_mgir_pack(mgir_pl);
+	err = mlxsw_reg_query(mlxsw_core, MLXSW_REG(mddt), mddt_pl);
+	if (err)
+		return err;
+
+	mlxsw_reg_mgir_fw_info_psid_memcpy_from(mgir_pl, psid);
+	return 0;
+}
+
 static int mlxsw_linecard_device_info_update(struct mlxsw_linecard *linecard)
 {
 	struct mlxsw_core *mlxsw_core = linecard->linecards->mlxsw_core;
···
 				      linecard->slot_index);
 			return 0;
 		}
+
+		err = mlxsw_linecard_device_psid_get(linecard, device_index,
+						     info.psid);
+		if (err)
+			return err;
+
 		linecard->device.info = info;
 		flashable_found = true;
 	} while (msg_seq);
···
 
 	if (linecard->active) {
 		struct mlxsw_linecard_device_info *info = &linecard->device.info;
+
+		err = devlink_info_version_fixed_put(req,
+						     DEVLINK_INFO_VERSION_GENERIC_FW_PSID,
+						     info->psid);
 
 		sprintf(buf, "%u.%u.%u", info->fw_major, info->fw_minor,
 			info->fw_sub_minor);