Unverified Commit eb56deaa authored Apr 30, 2026 by Conor Dooley Committed by Mark Brown May 04, 2026

spi: microchip-core-qspi: don't attempt to transmit during emulated read-only dual/quad operations

The core will deal with reads by creating clock cycles itself, there's
no need to generate clock cycles by transmitting garbage data at the
driver level. Further, transmitting garbage data just bricks the transfer
since QSPI doesn't have a dedicated master-out line like MOSI in regular
SPI. I'm not entirely sure if the transfer is bricked because of the
garbage data being transmitted on the bus or because the core loses
track of whether it is supposed to be sending or receiving data.

Fixes: 8f9cf02c ("spi: microchip-core-qspi: Add regular transfers")
CC: stable@vger.kernel.org
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://patch.msgid.link/20260430-freezing-saloon-95b1f3d9dad0@spud

Signed-off-by: Mark Brown <broonie@kernel.org>

parent 7672749e

drivers/spi/spi-microchip-core-qspi.c

+11 −1

Original line number	Diff line number	Diff line
		@@ -690,18 +690,28 @@ static int mchp_coreqspi_transfer_one(struct spi_controller *ctlr, struct spi_de
		struct spi_transfer *t)
		{
		struct mchp_coreqspi *qspi = spi_controller_get_devdata(ctlr);
		bool dual_quad = false;

		qspi->tx_len = t->len;

		if (t->tx_nbits == SPI_NBITS_QUAD \|\| t->rx_nbits == SPI_NBITS_QUAD \|\|
		t->tx_nbits == SPI_NBITS_DUAL \|\|
		t->rx_nbits == SPI_NBITS_DUAL)
		dual_quad = true;

		if (t->tx_buf)
		qspi->txbuf = (u8 *)t->tx_buf;

		if (!t->rx_buf) {
		mchp_coreqspi_write_op(qspi);
		} else {
		} else if (!dual_quad) {
		qspi->rxbuf = (u8 *)t->rx_buf;
		qspi->rx_len = t->len;
		mchp_coreqspi_write_read_op(qspi);
		} else {
		qspi->rxbuf = (u8 *)t->rx_buf;
		qspi->rx_len = t->len;
		mchp_coreqspi_read_op(qspi);
		}

		return 0;