spi: omap2-mcspi: Disable multi-mode when the previous message kept CS asserted

When the last transfer of a SPI message has the cs_change flag, the CS is kept
asserted after the message.
The next message can't use multi-mode because the CS will be briefly deasserted
before the first transfer.

Remove the early exit of the list_for_each_entry because the last transfer
actually needs to be always checked.

Fixes: d153ff4056cb ("spi: omap2-mcspi: Add support for MULTI-mode")
Signed-off-by: Félix Piédallu <felix.piedallu@non.se.com>
Link: https://patch.msgid.link/20250606-cs_change_fix-v1-2-27191a98a2e5@non.se.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index e834fb42fd4ba728578557d0eaa2fd57fe022c6d..70bb74b3bd9c324ecc787fb82c711b5d1afeb673 100644 (file)
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -134,6 +134,7 @@ struct omap2_mcspi {
        size_t                  max_xfer_len;
        u32                     ref_clk_hz;
        bool                    use_multi_mode;
+       bool                    last_msg_kept_cs;
 };
 
 struct omap2_mcspi_cs {
@@ -1269,6 +1270,10 @@ static int omap2_mcspi_prepare_message(struct spi_controller *ctlr,
         * multi-mode is applicable.
         */
        mcspi->use_multi_mode = true;
+
+       if (mcspi->last_msg_kept_cs)
+               mcspi->use_multi_mode = false;
+
        list_for_each_entry(tr, &msg->transfers, transfer_list) {
                if (!tr->bits_per_word)
                        bits_per_word = msg->spi->bits_per_word;
@@ -1289,22 +1294,17 @@ static int omap2_mcspi_prepare_message(struct spi_controller *ctlr,
 
                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)
+                       if (tr->cs_change) {
                                mcspi->use_multi_mode = false;
+                               mcspi->last_msg_kept_cs = true;
+                       } else {
+                               mcspi->last_msg_kept_cs = 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
-                *
-                * The bits_per_word of certain transfer can be different, but it will have no
-                * impact on the signal itself.
-                */
-               if (!mcspi->use_multi_mode)
-                       break;
        }
 
        omap2_mcspi_set_mode(ctlr);