spi: omap2-mcspi: Disable multi mode when CS should be kept asserted after message

When the last transfer of a SPI message has the cs_change flag, the CS is kept
asserted after the message.
Multi-mode can't respect this as CS is deasserted by the hardware at the end of
the message.

Disable multi-mode when not applicable to the current message.

Fixes: d153ff4 ("spi: omap2-mcspi: Add support for MULTI-mode")
Signed-off-by: Félix Piédallu <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Félix Piédallu

drivers/spi/spi-omap2-mcspi.c

@@ -1287,9 +1287,15 @@ static int omap2_mcspi_prepare_message(struct spi_controller *ctlr,
 			mcspi->use_multi_mode = false;
 		}
 
-		/* Check if transfer asks to change the CS status after the transfer */
-		if (!tr->cs_change)
-			mcspi->use_multi_mode = false;
+		if (list_is_last(&tr->transfer_list, &msg->transfers)) {
+			/* Check if transfer asks to keep the CS status after the whole message */
+			if (tr->cs_change)
+				mcspi->use_multi_mode = false;
+		} else {
+			/* Check if transfer asks to change the CS status after the transfer */
+			if (!tr->cs_change)
+				mcspi->use_multi_mode = false;
+		}
 
 		/*
 		 * If at least one message is not compatible, switch back to single mode