spi: lpspi: fix using CS discontinuously on i.MX8DXLEVK

SPI common code does not support using CS discontinuously for now.
However, i.MX8DXL-EVK only uses CS1 without CS0. Therefore, add a flag
is_only_cs1 to set the correct TCR[PCS].
Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
Link: https://lore.kernel.org/r/20200727031448.31661-4-xiaoning.wang@nxp.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-fsl-lpspi.c

@@ -98,6 +98,7 @@ struct fsl_lpspi_data {
 	struct clk *clk_ipg;
 	struct clk *clk_per;
 	bool is_slave;
+	bool is_only_cs1;
 	bool is_first_byte;
 
 	void *rx_buf;
@@ -257,10 +258,9 @@ static void fsl_lpspi_set_cmd(struct fsl_lpspi_data *fsl_lpspi)
 
 	temp |= fsl_lpspi->config.bpw - 1;
 	temp |= (fsl_lpspi->config.mode & 0x3) << 30;
+	temp |= (fsl_lpspi->config.chip_select & 0x3) << 24;
 	if (!fsl_lpspi->is_slave) {
 		temp |= fsl_lpspi->config.prescale << 27;
-		temp |= (fsl_lpspi->config.chip_select & 0x3) << 24;
-
 		/*
 		 * Set TCR_CONT will keep SS asserted after current transfer.
 		 * For the first transfer, clear TCR_CONTC to assert SS.
@@ -421,6 +421,9 @@ static int fsl_lpspi_setup_transfer(struct spi_controller *controller,
 	fsl_lpspi->config.mode = spi->mode;
 	fsl_lpspi->config.bpw = t->bits_per_word;
 	fsl_lpspi->config.speed_hz = t->speed_hz;
+	if (fsl_lpspi->is_only_cs1)
+		fsl_lpspi->config.chip_select = 1;
+	else
 		fsl_lpspi->config.chip_select = spi->chip_select;
 
 	if (!fsl_lpspi->config.speed_hz)
@@ -835,6 +838,8 @@ static int fsl_lpspi_probe(struct platform_device *pdev)
 	fsl_lpspi = spi_controller_get_devdata(controller);
 	fsl_lpspi->dev = &pdev->dev;
 	fsl_lpspi->is_slave = is_slave;
+	fsl_lpspi->is_only_cs1 = of_property_read_bool((&pdev->dev)->of_node,
+						"fsl,spi-only-use-cs1-sel");
 
 	controller->bits_per_word_mask = SPI_BPW_RANGE_MASK(8, 32);
 	controller->transfer_one = fsl_lpspi_transfer_one;