spi: spi_ll_stm32: fix slave frame shifting

In the current form of the code, the slave frame shifting leaves the TX
full and will shift out some unwanted bytes out on the next transaction.

Signed-off-by: Neil Armstrong <[email protected]>

Author: superna9999

drivers/spi/spi_ll_stm32.c

@@ -118,36 +118,30 @@ static void spi_stm32_shift_m(SPI_TypeDef *spi, struct spi_stm32_data *data)
 /* Shift a SPI frame as slave. */
 static void spi_stm32_shift_s(SPI_TypeDef *spi, struct spi_stm32_data *data)
 {
-	u16_t tx_frame;
-	u16_t rx_frame;
+	if (LL_SPI_IsActiveFlag_TXE(spi) && spi_context_tx_on(&data->ctx)) {
+		u16_t tx_frame = spi_stm32_next_tx(data);
 
-	tx_frame = spi_stm32_next_tx(data);
-	if (LL_SPI_IsActiveFlag_TXE(spi)) {
 		if (SPI_WORD_SIZE_GET(data->ctx.config->operation) == 8) {
 			LL_SPI_TransmitData8(spi, tx_frame);
-			/* The update is ignored if TX is off. */
 			spi_context_update_tx(&data->ctx, 1, 1);
 		} else {
 			LL_SPI_TransmitData16(spi, tx_frame);
-			/* The update is ignored if TX is off. */
 			spi_context_update_tx(&data->ctx, 2, 1);
 		}
+	} else {
+		LL_SPI_DisableIT_TXE(spi);
 	}
 
-	if (LL_SPI_IsActiveFlag_RXNE(spi)) {
+	if (LL_SPI_IsActiveFlag_RXNE(spi) && spi_context_rx_buf_on(&data->ctx)) {
+		u16_t rx_frame;
+
 		if (SPI_WORD_SIZE_GET(data->ctx.config->operation) == 8) {
 			rx_frame = LL_SPI_ReceiveData8(spi);
-			if (spi_context_rx_buf_on(&data->ctx)) {
-				UNALIGNED_PUT(rx_frame,
-					      (u8_t *)data->ctx.rx_buf);
-			}
+			UNALIGNED_PUT(rx_frame, (u8_t *)data->ctx.rx_buf);
 			spi_context_update_rx(&data->ctx, 1, 1);
 		} else {
 			rx_frame = LL_SPI_ReceiveData16(spi);
-			if (spi_context_rx_buf_on(&data->ctx)) {
-				UNALIGNED_PUT(rx_frame,
-					      (u16_t *)data->ctx.rx_buf);
-			}
+			UNALIGNED_PUT(rx_frame, (u16_t *)data->ctx.rx_buf);
 			spi_context_update_rx(&data->ctx, 2, 1);
 		}
 	}