spi: stm32h7: ensure message are smaller than max size

Ensure that messages given to transfer_one handler can actually be
handled by it. For that purpose rely on the SPI framework
spi_split_transfers_maxsize function to split messages whenever necessary.
Signed-off-by: Alain Volmat <alain.volmat@foss.st.com>
Link: https://lore.kernel.org/r/1612551572-495-5-git-send-email-alain.volmat@foss.st.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32.c

@@ -1004,6 +1004,20 @@ static int stm32_spi_prepare_msg(struct spi_master *master,
 		!!(spi_dev->mode & SPI_LSB_FIRST),
 		!!(spi_dev->mode & SPI_CS_HIGH));
 
+	/* On STM32H7, messages should not exceed a maximum size setted
+	 * afterward via the set_number_of_data function. In order to
+	 * ensure that, split large messages into several messages
+	 */
+	if (spi->cfg->set_number_of_data) {
+		int ret;
+
+		ret = spi_split_transfers_maxsize(master, msg,
+						  STM32H7_SPI_TSIZE_MAX,
+						  GFP_KERNEL | GFP_DMA);
+		if (ret)
+			return ret;
+	}
+
 	spin_lock_irqsave(&spi->lock, flags);
 
 	/* CPOL, CPHA and LSB FIRST bits have common register */