From: Vladimir Oltean olteanv@gmail.com
commit ca59d5a51690d5b9340343dc36792a252e9414ae upstream.
When used in Extended SPI mode on LS1021A, the DSPI controller wants to have the least significant 16-bit word written first to the TX FIFO.
In fact, the LS1021A reference manual says:
33.5.2.4.2 Draining the TX FIFO
When Extended SPI Mode (DSPIx_MCR[XSPI]) is enabled, if the frame size of SPI Data to be transmitted is more than 16 bits, then it causes two Data entries to be popped from TX FIFO simultaneously which are transferred to the shift register. The first of the two popped entries forms the 16 least significant bits of the SPI frame to be transmitted.
So given the following TX buffer:
+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | 0x0 | 0x1 | 0x2 | 0x3 | 0x4 | 0x5 | 0x6 | 0x7 | 0x8 | 0x9 | 0xa | 0xb | +-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+ | 32-bit word 1 | 32-bit word 2 | 32-bit word 3 | +-----------------------+-----------------------+-----------------------+
The correct way that a little-endian system should transmit it on the wire when bits_per_word is 32 is:
0x03020100 0x07060504 0x0b0a0908
But it is actually transmitted as following, as seen with a scope:
0x01000302 0x05040706 0x09080b0a
It appears that this patch has been submitted at least once before: https://lkml.org/lkml/2018/9/21/286 but in that case Chuanhua Han did not manage to explain the problem clearly enough and the patch did not get merged, leaving XSPI mode broken.
Fixes: 8fcd151d2619 ("spi: spi-fsl-dspi: XSPI FIFO handling (in TCFQ mode)") Cc: Esben Haabendal eha@deif.com Cc: Chuanhua Han chuanhua.han@nxp.com Signed-off-by: Vladimir Oltean olteanv@gmail.com Link: https://lore.kernel.org/r/20191228135536.14284-1-olteanv@gmail.com Signed-off-by: Mark Brown broonie@kernel.org Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/spi/spi-fsl-dspi.c | 15 ++++----------- 1 file changed, 4 insertions(+), 11 deletions(-)
--- a/drivers/spi/spi-fsl-dspi.c +++ b/drivers/spi/spi-fsl-dspi.c @@ -583,21 +583,14 @@ static void dspi_tcfq_write(struct fsl_d dspi->tx_cmd |= SPI_PUSHR_CMD_CTCNT;
if (dspi->devtype_data->xspi_mode && dspi->bits_per_word > 16) { - /* Write two TX FIFO entries first, and then the corresponding - * CMD FIFO entry. + /* Write the CMD FIFO entry first, and then the two + * corresponding TX FIFO entries. */ u32 data = dspi_pop_tx(dspi);
- if (dspi->cur_chip->ctar_val & SPI_CTAR_LSBFE) { - /* LSB */ - tx_fifo_write(dspi, data & 0xFFFF); - tx_fifo_write(dspi, data >> 16); - } else { - /* MSB */ - tx_fifo_write(dspi, data >> 16); - tx_fifo_write(dspi, data & 0xFFFF); - } cmd_fifo_write(dspi); + tx_fifo_write(dspi, data & 0xFFFF); + tx_fifo_write(dspi, data >> 16); } else { /* Write one entry to both TX FIFO and CMD FIFO * simultaneously.