usrp2: increased transport buffer minimum size, and added warning

added more notes on buffer size to the manual

pulled in some firmware fixes from the mimo work, just to have them in here

3 files changed, 25 insertions, 14 deletions

diff --git a/host/docs/usrp2.rst b/host/docs/usrp2.rst
index 09987b3fa..aff0d0454 100644
--- a/host/docs/usrp2.rst
+++ b/host/docs/usrp2.rst
@@ -158,10 +158,25 @@ buffer incoming samples faster than they can be processed.
 However, if you application cannot process samples fast enough,
 no amount of buffering can save you.
 
+By default, the UHD will try to request a reasonably large buffer size for both send and receive.
+A warning will be printed on instantiation if the actual buffer size is insufficient.
+See the OS specific notes below:
+
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+OS specific notes
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+On linux, the maximum buffer sizes are capped by the sysctl values
+**net.core.rmem_max** and **net.core.wmem_max**.
+To change the maximum values, run the following commands:
+::
+
+    sudo sysctl -w net.core.rmem_max=<new value>
+    sudo sysctl -w net.core.wmem_max=<new value>
+
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 Device address params
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-To set the size of the buffers,
+To manually set the size of the buffers,
 the usrp2 will accept two optional parameters in the device address.
 Each parameter will accept a numeric value for the number of bytes.
 
@@ -172,14 +187,3 @@ Example, set the args string to the following:
 ::
 
     addr=192.168.10.2, recv_buff_size=100e6
-
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-OS specific notes
-^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-On linux, the maximum buffer sizes are capped by the sysctl values
-**net.core.rmem_max** and **net.core.wmem_max**.
-To change the maximum values, run the following commands:
-::
-
-    sudo sysctl -w net.core.rmem_max=<new value>
-    sudo sysctl -w net.core.wmem_max=<new value>
diff --git a/host/lib/transport/udp_zero_copy_asio.cpp b/host/lib/transport/udp_zero_copy_asio.cpp
index c3c02707e..7f9292d24 100644
--- a/host/lib/transport/udp_zero_copy_asio.cpp
+++ b/host/lib/transport/udp_zero_copy_asio.cpp
@@ -27,7 +27,8 @@ using namespace uhd::transport;
 /***********************************************************************
  * Constants
  **********************************************************************/
-static const size_t MIN_SOCK_BUFF_SIZE = size_t(100e3);
+//enough buffering for half a second of samples at full rate on usrp2
+static const size_t MIN_SOCK_BUFF_SIZE = size_t(sizeof(boost::uint32_t) * 25e6 * 0.5);
 static const size_t MAX_DGRAM_SIZE = 1500; //assume max size on send and recv
 static const double RECV_TIMEOUT = 0.1; //100 ms
 
@@ -159,6 +160,12 @@ template<typename Opt> static void resize_buff_helper(
     //otherwise, ensure that the buffer is at least the minimum size
     else if (udp_trans->get_buff_size<Opt>() < MIN_SOCK_BUFF_SIZE){
         resize_buff_helper<Opt>(udp_trans, MIN_SOCK_BUFF_SIZE, name);
+        if (udp_trans->get_buff_size<Opt>() < MIN_SOCK_BUFF_SIZE){
+            std::cerr << boost::format(
+                "Warning: the %s buffer size is smaller than the recommended size of %d bytes.\n"
+                "    See the USRP2 application notes on buffer resizing."
+            ) % name % MIN_SOCK_BUFF_SIZE << std::endl;
+        }
     }
 }
 
diff --git a/host/lib/usrp/usrp2/usrp2_iface.cpp b/host/lib/usrp/usrp2/usrp2_iface.cpp
index 83e98904e..66a1a57f6 100644
--- a/host/lib/usrp/usrp2/usrp2_iface.cpp
+++ b/host/lib/usrp/usrp2/usrp2_iface.cpp
@@ -200,7 +200,7 @@ private:
         //send and recv
         usrp2_ctrl_data_t in_data = this->ctrl_send_and_recv(out_data);
         UHD_ASSERT_THROW(htonl(in_data.id) == USRP2_CTRL_ID_WOAH_I_DEFINITELY_PEEKED_IT_DUDE);
-        return T(ntohl(out_data.data.poke_args.data));
+        return T(ntohl(in_data.data.poke_args.data));
     }
 
 };