Update omap_mcspi_setup_transfer() so that the driver supports
communication over a single data line for 3-wire SPI devices.

Signed-off-by: Antoni Pokusinski <apokusinski01@gmail.com>

---
 drivers/spi/spi-omap2-mcspi.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi-omap2-mcspi.c b/drivers/spi/spi-omap2-mcspi.c
index 70bb74b3bd9c..bf4c3770bc7f 100644
--- a/drivers/spi/spi-omap2-mcspi.c
+++ b/drivers/spi/spi-omap2-mcspi.c
@@ -943,10 +943,16 @@ static int omap2_mcspi_setup_transfer(struct spi_device *spi,
 
 	l = mcspi_cached_chconf0(spi);
 
-	/* standard 4-wire host mode:  SCK, MOSI/out, MISO/in, nCS
-	 * REVISIT: this controller could support SPI_3WIRE mode.
-	 */
-	if (mcspi->pin_dir == MCSPI_PINDIR_D0_IN_D1_OUT) {
+	if (spi->mode & SPI_3WIRE) {
+		if (t && !t->tx_buf) {
+			l &= ~OMAP2_MCSPI_CHCONF_IS;
+			l |= OMAP2_MCSPI_CHCONF_DPE0;
+		} else if (t && !t->rx_buf) {
+			l |= OMAP2_MCSPI_CHCONF_IS;
+			l &= ~OMAP2_MCSPI_CHCONF_DPE0;
+		}
+		l |= OMAP2_MCSPI_CHCONF_DPE1;
+	} else if (mcspi->pin_dir == MCSPI_PINDIR_D0_IN_D1_OUT) {
 		l &= ~OMAP2_MCSPI_CHCONF_IS;
 		l &= ~OMAP2_MCSPI_CHCONF_DPE1;
 		l |= OMAP2_MCSPI_CHCONF_DPE0;
@@ -1179,6 +1185,7 @@ static int omap2_mcspi_transfer_one(struct spi_controller *ctlr,
 		omap2_mcspi_set_cs(spi, spi->mode & SPI_CS_HIGH);
 
 	if (par_override ||
+	    (spi->mode & SPI_3WIRE) ||
 	    (t->speed_hz != spi->max_speed_hz) ||
 	    (t->bits_per_word != spi->bits_per_word)) {
 		par_override = 1;
@@ -1486,7 +1493,7 @@ static int omap2_mcspi_probe(struct platform_device *pdev)
 		return -ENOMEM;
 
 	/* the spi->mode bits understood by this driver: */
-	ctlr->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
+	ctlr->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH | SPI_3WIRE;
 	ctlr->bits_per_word_mask = SPI_BPW_RANGE_MASK(4, 32);
 	ctlr->setup = omap2_mcspi_setup;
 	ctlr->auto_runtime_pm = true;
-- 
2.53.0

On Sat, 14 Feb 2026 22:28:00 +0100, Antoni Pokusinski wrote:
> Update omap_mcspi_setup_transfer() so that the driver supports
> communication over a single data line for 3-wire SPI devices.
> 
> 

Applied to

   https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git for-next

Thanks!

[1/1] spi: omap2-mcspi: add support for 3-wire transfers
      commit: 6f7e9b11549dc726270a7e8539201d4270f15803

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

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Thanks,
Mark