diff --git a/drivers/rpmsg/rpmsg_port_spi.c b/drivers/rpmsg/rpmsg_port_spi.c
index 1961372621..1a2f6874a8 100644
--- a/drivers/rpmsg/rpmsg_port_spi.c
+++ b/drivers/rpmsg/rpmsg_port_spi.c
@@ -45,6 +45,8 @@
 #  define rpmsg_port_spi_crc16(hdr) 0
 #endif
 
+#define BYTES2WORDS(s,b)            ((b) / ((s)->nbits >> 3))
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -70,6 +72,7 @@ struct rpmsg_port_spi_s
   /* SPI devices' configuration */
 
   uint32_t                       devid;
+  int                            nbits;
 
   /* Reserved for cmd send */
 
@@ -292,7 +295,8 @@ static int rpmsg_port_spi_sreq_handler(FAR struct ioexpander_dev_s *dev,
   rpmsginfo("irq send cmd:%u avail:%u\n", txhdr->cmd, txhdr->avail);
 
   SPI_SELECT(rpspi->spi, rpspi->devid, true);
-  SPI_EXCHANGE(rpspi->spi, txhdr, rpspi->rxhdr, rpspi->cmdhdr->len);
+  SPI_EXCHANGE(rpspi->spi, txhdr, rpspi->rxhdr,
+               BYTES2WORDS(rpspi, rpspi->cmdhdr->len));
 
   rpspi->rxavail = txhdr->avail;
   return 0;
@@ -470,7 +474,7 @@ rpmsg_port_spi_init_hardware(FAR struct rpmsg_port_spi_s *rpspi,
       return ret;
     }
 
-  SPI_SETBITS(spi, 8);
+  SPI_SETBITS(spi, spicfg->nbits);
   SPI_SETMODE(spi, spicfg->mode);
   SPI_SETFREQUENCY(spi, spicfg->freq);
   SPI_REGISTERCALLBACK(spi, rpmsg_port_spi_complete_handler, rpspi);
@@ -479,6 +483,7 @@ rpmsg_port_spi_init_hardware(FAR struct rpmsg_port_spi_s *rpspi,
   rpspi->spi = spi;
   rpspi->ioe = ioe;
   rpspi->devid = spicfg->devid;
+  rpspi->nbits = spicfg->nbits;
 
   return 0;
 }
diff --git a/drivers/rpmsg/rpmsg_port_spi_slave.c b/drivers/rpmsg/rpmsg_port_spi_slave.c
index da2679a08e..6d8f0099d2 100644
--- a/drivers/rpmsg/rpmsg_port_spi_slave.c
+++ b/drivers/rpmsg/rpmsg_port_spi_slave.c
@@ -46,6 +46,8 @@
 #  define rpmsg_port_spi_crc16(hdr) 0
 #endif
 
+#define BYTES2WORDS(s,b)            ((b) / ((s)->nbits >> 3))
+
 /****************************************************************************
  * Private Types
  ****************************************************************************/
@@ -69,11 +71,17 @@ struct rpmsg_port_spi_s
   uint8_t                        mreq;
   uint8_t                        sreq;
 
+  /* SPI devices' configuration */
+
+  int                            nbits;
+
   /* Reserved for cmd send */
 
   FAR struct rpmsg_port_header_s *cmdhdr;
 
-  /* Used for sync data state between sreq_handler and complete_handler */
+  /* Used for sync data state between mreq_handler and
+   * rpmsg_port_spi_slave_notify
+   */
 
   FAR struct rpmsg_port_header_s *txhdr;
   FAR struct rpmsg_port_header_s *rxhdr;
@@ -193,7 +201,8 @@ void rpmsg_port_spi_exchange(FAR struct rpmsg_port_spi_s *rpspi)
 
   rpmsginfo("send cmd:%u avail:%u\n", txhdr->cmd, txhdr->avail);
 
-  SPIS_CTRLR_ENQUEUE(rpspi->spictrlr, txhdr, rpspi->cmdhdr->len);
+  SPIS_CTRLR_ENQUEUE(rpspi->spictrlr, txhdr,
+                     BYTES2WORDS(rpspi, rpspi->cmdhdr->len));
   IOEXP_WRITEPIN(rpspi->ioe, rpspi->sreq, 1);
 
   rpspi->rxavail = txhdr->avail;
@@ -277,7 +286,7 @@ static size_t rpmsg_port_spi_slave_getdata(FAR struct spi_slave_dev_s *dev,
     container_of(dev, struct rpmsg_port_spi_s, spislv);
 
   *data = rpspi->rxhdr;
-  return rpspi->cmdhdr->len;
+  return BYTES2WORDS(rpspi, rpspi->cmdhdr->len);
 }
 
 /****************************************************************************
@@ -543,7 +552,8 @@ rpmsg_port_spi_init_hardware(FAR struct rpmsg_port_spi_s *rpspi,
   rpspi->ioe = ioe;
   rpspi->spictrlr = spictrlr;
   rpspi->spislv.ops = &g_rpmsg_port_spi_slave_ops;
-  SPIS_CTRLR_BIND(spictrlr, &rpspi->spislv, spicfg->mode, 8);
+  SPIS_CTRLR_BIND(spictrlr, &rpspi->spislv, spicfg->mode, spicfg->nbits);
+  rpspi->nbits = spicfg->nbits;
 
   return 0;
 }
diff --git a/include/nuttx/rpmsg/rpmsg_port.h b/include/nuttx/rpmsg/rpmsg_port.h
index 540d8d46e9..b102ffd788 100644
--- a/include/nuttx/rpmsg/rpmsg_port.h
+++ b/include/nuttx/rpmsg/rpmsg_port.h
@@ -79,6 +79,7 @@ struct rpmsg_port_spi_config_s
   int             sreq_invert; /* Pin options described in ioexpander.h */
 
   int             mode;        /* Mode of enum spi_mode_e */
+  int             nbits;
   uint32_t        devid;       /* Device ID of enum spi_devtype_e */
   uint32_t        freq;        /* SPI frequency (Hz) */
 };