Device3: Change packet-based flow control to byte-based flow control

6 files changed, 28 insertions, 20 deletions

diff --git a/host/include/uhd/rfnoc/constants.hpp b/host/include/uhd/rfnoc/constants.hpp
index 6df4c535f..bda4c6440 100644
--- a/host/include/uhd/rfnoc/constants.hpp
+++ b/host/include/uhd/rfnoc/constants.hpp
@@ -25,7 +25,7 @@ static const std::string XML_PATH_ENV = "UHD_RFNOC_DIR";
 //! If the block name can't be automatically detected, this name is used
 static const std::string DEFAULT_BLOCK_NAME = "Block";
 static const uint64_t DEFAULT_NOC_ID = 0xFFFFFFFFFFFFFFFF;
-static const size_t NOC_SHELL_COMPAT_MAJOR = 3;
+static const size_t NOC_SHELL_COMPAT_MAJOR = 4;
 static const size_t NOC_SHELL_COMPAT_MINOR = 0;
 
 static const size_t MAX_PACKET_SIZE = 8000; // bytes
@@ -35,7 +35,7 @@ static const size_t DEFAULT_PACKET_SIZE = 1456; // bytes
 static const size_t BYTES_PER_LINE = 8;
 
 //! For flow control within a single crossbar
-static const size_t DEFAULT_FC_XBAR_PKTS_PER_ACK = 2;
+static const size_t DEFAULT_FC_XBAR_RESPONSE_FREQ = 8;
 //! For flow control when data is flowing from device to host (rx)
 static const size_t DEFAULT_FC_RX_RESPONSE_FREQ = 64; // ACKs per flow control window
 //! For flow control when data is flowing from host to device (tx)
@@ -48,15 +48,15 @@ static const size_t DEFAULT_FC_TX_RESPONSE_FREQ = 8; // ACKs per flow control wi
 static const double DEFAULT_FC_RX_SW_BUFF_FULL_FACTOR = 0.80;
 
 // Common settings registers.
-static const uint32_t SR_FLOW_CTRL_CYCS_PER_ACK          = 0;
-static const uint32_t SR_FLOW_CTRL_PKTS_PER_ACK          = 1;
+static const uint32_t SR_FLOW_CTRL_BYTES_PER_ACK         = 1;
 static const uint32_t SR_FLOW_CTRL_WINDOW_SIZE           = 2;
-static const uint32_t SR_FLOW_CTRL_WINDOW_EN             = 3;
+static const uint32_t SR_FLOW_CTRL_EN                    = 3;
 static const uint32_t SR_ERROR_POLICY                    = 4;
 static const uint32_t SR_BLOCK_SID                       = 5; // TODO rename to SRC_SID
 static const uint32_t SR_NEXT_DST_SID                    = 6;
 static const uint32_t SR_RESP_IN_DST_SID                 = 7;
 static const uint32_t SR_RESP_OUT_DST_SID                = 8;
+static const uint32_t SR_FLOW_CTRL_PKT_LIMIT             = 9;
 
 static const uint32_t SR_READBACK_ADDR                   = 124;
 static const uint32_t SR_READBACK                        = 127;
diff --git a/host/include/uhd/rfnoc/graph.hpp b/host/include/uhd/rfnoc/graph.hpp
index f92e6b528..d7b7cc43e 100644
--- a/host/include/uhd/rfnoc/graph.hpp
+++ b/host/include/uhd/rfnoc/graph.hpp
@@ -67,12 +67,12 @@ public:
      *
      * \param sink_block Sink block ID
      * \param dst_block_port Destination (sink) block port
-     * \param pkts_per_ack Flow controlf frequency in packets
+     * \param bytes_per_ack Flow control frequency in bytes
      */
     virtual void connect_sink(
             const block_id_t &sink_block,
             const size_t dst_block_port,
-            const size_t pkts_per_ack
+            const size_t bytes_per_ack
     ) = 0;
 
     virtual std::string get_name() const = 0;
diff --git a/host/include/uhd/rfnoc/sink_block_ctrl_base.hpp b/host/include/uhd/rfnoc/sink_block_ctrl_base.hpp
index ec3f28e32..f90361cf1 100644
--- a/host/include/uhd/rfnoc/sink_block_ctrl_base.hpp
+++ b/host/include/uhd/rfnoc/sink_block_ctrl_base.hpp
@@ -70,20 +70,17 @@ public:
      * send out ACKs, telling the upstream block which packets have been consumed,
      * so the upstream block can increase his flow control credit.
      *
-     * In the default implementation, this just sets registers
-     * SR_FLOW_CTRL_CYCS_PER_ACK and SR_FLOW_CTRL_PKTS_PER_ACK accordingly.
+     * In the default implementation, this just sets register SR_FLOW_CTRL_PKTS_PER_ACK
+     * accordingly.
      *
      * Override this function if your block has port-specific flow control settings.
      *
-     * \param cycles Send an ACK after this many clock cycles.
-     *               Setting this to zero disables this type of flow control acknowledgement.
-     * \param packets Send an ACK after this many packets have been consumed.
-     *               Setting this to zero disables this type of flow control acknowledgement.
+     * \param bytes Send an ACK after this many bytes have been consumed.
+     *              Setting this to zero disables flow control acknowledgement.
      * \param block_port Set up flow control for a stream coming in on this particular block port.
      */
     virtual void configure_flow_control_in(
-            size_t cycles,
-            size_t packets,
+            size_t bytes,
             size_t block_port=0
     );
 
diff --git a/host/include/uhd/rfnoc/source_block_ctrl_base.hpp b/host/include/uhd/rfnoc/source_block_ctrl_base.hpp
index 7d0a65107..39e7411f3 100644
--- a/host/include/uhd/rfnoc/source_block_ctrl_base.hpp
+++ b/host/include/uhd/rfnoc/source_block_ctrl_base.hpp
@@ -97,15 +97,23 @@ public:
      *
      * Override this function if your block has port-specific flow control settings.
      *
-     * \param buf_size_pkts The size of the downstream block's input FIFO size in number of packets. Setting
-     *                      this to zero disables flow control. The block will then produce data as fast as it can.
-     *                     \b Warning: This can cause head-of-line blocking, and potentially lock up your device!
+     * \param enable_output Enable flow control module's output. If disabled, no packets will be output
+     *                      regardless of flow control state.
+     * \param buf_size_bytes The size of the downstream block's input FIFO size in number of bytes. Setting
+     *                       this to zero disables byte based flow control. If both byte based flow control and
+     *                       the packet limit are set to zero, the block will then produce data as fast as it can.
+     *                       \b Warning: This can cause head-of-line blocking, and potentially lock up your device!
+     * \param pkt_limit Limit the maximum number of packets in flight. Setting this to zero disables packet limiting.
+     *                  Usually kept disabled except for special case connections (such as DMA) that support only
+     *                  a finite number of packets in flight.
      * \param block_port Specify on which outgoing port this setting is valid.
      * \param sid The SID for which this is valid. This is meant for cases where the outgoing block port is
      *            not sufficient to set the flow control, and as such is rarely used.
      */
     virtual void configure_flow_control_out(
-            size_t buf_size_pkts,
+            bool enable_output,
+            size_t buf_size_bytes,
+            size_t pkt_limit=0,
             size_t block_port=0,
             const uhd::sid_t &sid=uhd::sid_t()
      );
diff --git a/host/include/uhd/transport/CMakeLists.txt b/host/include/uhd/transport/CMakeLists.txt
index 3ce06b5b1..785e2d53d 100644
--- a/host/include/uhd/transport/CMakeLists.txt
+++ b/host/include/uhd/transport/CMakeLists.txt
@@ -20,6 +20,7 @@ UHD_INSTALL(FILES
     usb_device_handle.hpp
     vrt_if_packet.hpp
     zero_copy.hpp
+    zero_copy_flow_ctrl.hpp
     DESTINATION ${INCLUDE_DIR}/uhd/transport
     COMPONENT headers
 )
diff --git a/host/include/uhd/transport/vrt_if_packet.hpp b/host/include/uhd/transport/vrt_if_packet.hpp
index 579ac77d2..07792f13f 100644
--- a/host/include/uhd/transport/vrt_if_packet.hpp
+++ b/host/include/uhd/transport/vrt_if_packet.hpp
@@ -68,6 +68,8 @@ namespace vrt{
         bool sob, eob;
         //! This is asserted for command responses that are errors (CHDR only)
         bool error;
+        //! This is asserted for flow control packets are ACKS (CHDR only)
+        bool fc_ack;
 
         //optional fields
         //! Stream ID (SID). See uhd::sid_t
@@ -185,7 +187,7 @@ namespace vrt{
         num_packet_words32(0),
         packet_count(0),
         sob(false), eob(false),
-        error(false),
+        error(false), fc_ack(false),
         has_sid(false), sid(0),
         has_cid(false), cid(0),
         has_tsi(false), tsi(0),