mimxrt10xx: Factor out "transfer_common"

.. and set the "MasterPcsContinuous" flag, which removes some of the
gap between bytes of a single SPI transaction

Author: jepler

ports/mimxrt10xx/common-hal/busio/SPI.c

@@ -283,6 +283,21 @@ void common_hal_busio_spi_unlock(busio_spi_obj_t *self) {
     self->has_lock = false;
 }
 
+static status_t transfer_common(busio_spi_obj_t *self, lpspi_transfer_t *xfer) {
+    xfer->configFlags = kLPSPI_MasterPcsContinuous;
+
+    status_t status;
+    int retries = MAX_SPI_BUSY_RETRIES;
+    do {
+        status = LPSPI_MasterTransferBlocking(self->spi, xfer);
+    } while (status == kStatus_LPSPI_Busy && --retries > 0);
+
+    if (status != kStatus_Success) {
+        printf("%s: status %ld\r\n", __func__, status);
+    }
+    return status;
+}
+
 bool common_hal_busio_spi_write(busio_spi_obj_t *self,
     const uint8_t *data, size_t len) {
     if (len == 0) {
@@ -295,17 +310,8 @@ bool common_hal_busio_spi_write(busio_spi_obj_t *self,
     lpspi_transfer_t xfer = { 0 };
     xfer.txData = (uint8_t *)data;
     xfer.dataSize = len;
-    xfer.configFlags = kLPSPI_MasterPcs0;
 
-    status_t status;
-    int retries = MAX_SPI_BUSY_RETRIES;
-    do {
-        status = LPSPI_MasterTransferBlocking(self->spi, &xfer);
-    } while (status == kStatus_LPSPI_Busy && --retries > 0);
-
-    if (status != kStatus_Success) {
-        printf("%s: status %ld\r\n", __func__, status);
-    }
+    status_t status = transfer_common(self, &xfer);
 
     return status == kStatus_Success;
 }
@@ -325,15 +331,7 @@ bool common_hal_busio_spi_read(busio_spi_obj_t *self,
     xfer.rxData = data;
     xfer.dataSize = len;
 
-    status_t status;
-    int retries = MAX_SPI_BUSY_RETRIES;
-    do {
-        status = LPSPI_MasterTransferBlocking(self->spi, &xfer);
-    } while (status == kStatus_LPSPI_Busy && --retries > 0);
-
-    if (status != kStatus_Success) {
-        printf("%s: status %ld\r\n", __func__, status);
-    }
+    status_t status = transfer_common(self, &xfer);
 
     return status == kStatus_Success;
 }
@@ -353,15 +351,7 @@ bool common_hal_busio_spi_transfer(busio_spi_obj_t *self, const uint8_t *data_ou
     xfer.rxData = data_in;
     xfer.dataSize = len;
 
-    status_t status;
-    int retries = MAX_SPI_BUSY_RETRIES;
-    do {
-        status = LPSPI_MasterTransferBlocking(self->spi, &xfer);
-    } while (status == kStatus_LPSPI_Busy && --retries > 0);
-
-    if (status != kStatus_Success) {
-        printf("%s: status %ld\r\n", __func__, status);
-    }
+    status_t status = transfer_common(self, &xfer);
 
     return status == kStatus_Success;
 }