Add a generic function for tx write out of order (timestamps not increasing)

Add an API to allow out-of-order writes to a radio interface, unlike the
current interface.

this function is called in UE in this commit, even if the tx might
still be in order.

Later, i plan to improve UE pulti-threading, that will lead to out of
order tx.  also, the gNB will benefit of this new function to replace
several specific pieces of code that reorder tx with over complex and
slow systems

radio/COMMON/common_lib.c

@@ -43,6 +43,7 @@
 //#include "targets/RT/USER/lte-softmodem.h"
 #include "executables/softmodem-common.h"
 
+#define MAX_GAP 100ULL
 const char *const devtype_names[MAX_RF_DEV_TYPE] =
     {"", "USRP B200", "USRP X300", "USRP N300", "USRP X400", "BLADERF", "LMSSDR", "IRIS", "No HW", "UEDv2", "RFSIMULATOR"};
 
@@ -173,3 +174,98 @@ int openair0_transport_load(openair0_device *device,
 
   return rc;
 }
+
+static void writerEnqueue(re_order_t *ctx, openair0_timestamp timestamp, void **txp, int nsamps, int nbAnt, int flags)
+{
+  pthread_mutex_lock(&ctx->mutex_store);
+  LOG_D(HW, "Enqueue write for TS: %lu\n", timestamp);
+  int i;
+  for (i = 0; i < WRITE_QUEUE_SZ; i++)
+    if (!ctx->queue[i].active) {
+      ctx->queue[i].timestamp = timestamp;
+      ctx->queue[i].active = true;
+      ctx->queue[i].nsamps = nsamps;
+      ctx->queue[i].nbAnt = nbAnt;
+      ctx->queue[i].flags = flags;
+      AssertFatal(nbAnt <= NB_ANTENNAS_TX, "");
+      for (int j = 0; j < nbAnt; j++)
+        ctx->queue[i].txp[j] = txp[j];
+      break;
+    }
+  AssertFatal(i < WRITE_QUEUE_SZ, "Write queue full\n");
+  pthread_mutex_unlock(&ctx->mutex_store);
+}
+
+static void writerProcessWaitingQueue(openair0_device *device)
+{
+  bool found = false;
+  re_order_t *ctx = &device->reOrder;
+  do {
+    found = false;
+    pthread_mutex_lock(&ctx->mutex_store);
+    for (int i = 0; i < WRITE_QUEUE_SZ; i++) {
+      if (ctx->queue[i].active && llabs(ctx->queue[i].timestamp - ctx->nextTS) < MAX_GAP) {
+        openair0_timestamp timestamp = ctx->queue[i].timestamp;
+        LOG_D(HW, "Dequeue write for TS: %lu\n", timestamp);
+        int nsamps = ctx->queue[i].nsamps;
+        int nbAnt = ctx->queue[i].nbAnt;
+        int flags = ctx->queue[i].flags;
+        void *txp[NB_ANTENNAS_TX];
+        AssertFatal(nbAnt <= NB_ANTENNAS_TX, "");
+        for (int j = 0; j < nbAnt; j++)
+          txp[j] = ctx->queue[i].txp[j];
+        ctx->queue[i].active = false;
+        pthread_mutex_unlock(&ctx->mutex_store);
+        found = true;
+        if (flags || IS_SOFTMODEM_RFSIM) {
+          int wroteSamples = device->trx_write_func(device, timestamp, txp, nsamps, nbAnt, flags);
+          if (wroteSamples != nsamps)
+            LOG_E(HW, "Failed to write to rf\n");
+        }
+        ctx->nextTS += nsamps;
+        pthread_mutex_lock(&ctx->mutex_store);
+      }
+    }
+    pthread_mutex_unlock(&ctx->mutex_store);
+  } while (found);
+}
+
+// We assume the data behind *txp are permanently allocated
+// When we will go further, we can remove all RC.xxx.txdata buffers in xNB, in UE
+// but to make zerocopy and agnostic design, we need to make a proper ring buffer with mutex protection
+// mutex (or atomic flags) will be mandatory because this out order system root cause is there are several writer threads
+
+int openair0_write_reorder(openair0_device *device, openair0_timestamp timestamp, void **txp, int nsamps, int nbAnt, int flags)
+{
+  int wroteSamples = 0;
+  re_order_t *ctx = &device->reOrder;
+  LOG_D(HW, "received write order ts: %lu, nb samples %d, next ts %luflags %d\n", timestamp, nsamps, timestamp + nsamps, flags);
+  if (!ctx->initDone) {
+    ctx->nextTS = timestamp;
+    pthread_mutex_init(&ctx->mutex_write, NULL);
+    pthread_mutex_init(&ctx->mutex_store, NULL);
+    ctx->initDone = true;
+  }
+  if (pthread_mutex_trylock(&ctx->mutex_write) == 0) {
+    // We have the write exclusivity
+    if (llabs(timestamp - ctx->nextTS) < MAX_GAP) { // We are writing in sequence of the previous write
+      if (flags || IS_SOFTMODEM_RFSIM)
+        wroteSamples = device->trx_write_func(device, timestamp, txp, nsamps, nbAnt, flags);
+      else
+        wroteSamples = nsamps;
+      ctx->nextTS += nsamps;
+
+    } else {
+      writerEnqueue(ctx, timestamp, txp, nsamps, nbAnt, flags);
+    }
+    writerProcessWaitingQueue(device);
+    pthread_mutex_unlock(&ctx->mutex_write);
+    return wroteSamples ? wroteSamples : nsamps;
+  }
+  writerEnqueue(ctx, timestamp, txp, nsamps, nbAnt, flags);
+  if (pthread_mutex_trylock(&ctx->mutex_write) == 0) {
+    writerProcessWaitingQueue(device);
+    pthread_mutex_unlock(&ctx->mutex_write);
+  }
+  return nsamps;
+}

radio/COMMON/common_lib.h

@@ -384,6 +384,22 @@ typedef struct fhstate_s {
   int active;
 } fhstate_t;
 
+#define WRITE_QUEUE_SZ 20
+typedef struct {
+  bool initDone;
+  pthread_mutex_t mutex_write;
+  pthread_mutex_t mutex_store;
+  openair0_timestamp nextTS;
+  struct {
+    bool active;
+    openair0_timestamp timestamp;
+    void *txp[NB_ANTENNAS_TX];
+    int nsamps;
+    int nbAnt;
+    int flags;
+  } queue[WRITE_QUEUE_SZ];
+} re_order_t;
+
 /*!\brief structure holds the parameters to configure USRP devices */
 struct openair0_device_t {
   /*!tx write thread*/
@@ -586,6 +602,7 @@ struct openair0_device_t {
   /* \brief timing statistics for TX fronthaul (ethernet)
    */
   time_stats_t tx_fhaul;
+  re_order_t reOrder;
 };
 
 /* type of device init function, implemented in shared lib */
@@ -654,6 +671,7 @@ extern int read_recplayconfig(recplay_conf_t **recplay_conf, recplay_state_t **r
 /*! \brief store recorded iqs from memory to file. */
 extern void iqrecorder_end(openair0_device *device);
 
+int openair0_write_reorder(openair0_device *device, openair0_timestamp timestamp, void **txp, int nsamps, int nbAnt, int flags);
 
 #include <unistd.h>
 #ifndef gettid