[PATCH 2/3] spi: orion: enable support for switching CS every transferred byte

[<kostap@xxxxxxxxxxx>]

From: Marcin Wojtas <mw@xxxxxxxxxxxx>

Some SPI devices, such as SLIC (Subscriber Line Interface Card)
require toggling the CS every transferred byte. Enable such
possibility by creating a new DT property and enabling SPI
device mode update. Add according support in the spi-orion driver.

Signed-off-by: Marcin Wojtas <mw@xxxxxxxxxxxx>
Signed-off-by: Konstantin Porotchkin <kostap@xxxxxxxxxxx>
---
 drivers/spi/spi-orion.c | 20 +++++++++++++++++++-
 drivers/spi/spi.c       |  6 ++++--
 include/linux/spi/spi.h |  1 +
 3 files changed, 24 insertions(+), 3 deletions(-)

diff --git a/drivers/spi/spi-orion.c b/drivers/spi/spi-orion.c
index 3bfda4225d45..7db9034b0879 100644
--- a/drivers/spi/spi-orion.c
+++ b/drivers/spi/spi-orion.c
@@ -369,8 +369,15 @@ orion_spi_write_read_8bit(struct spi_device *spi,
 {
 	void __iomem *tx_reg, *rx_reg, *int_reg;
 	struct orion_spi *orion_spi;
+	bool cs_single_byte;
+
+	cs_single_byte = spi->mode & SPI_1BYTE_CS;
 
 	orion_spi = spi_master_get_devdata(spi->master);
+
+	if (cs_single_byte)
+		orion_spi_set_cs(spi, 0);
+
 	tx_reg = spi_reg(orion_spi, ORION_SPI_DATA_OUT_REG);
 	rx_reg = spi_reg(orion_spi, ORION_SPI_DATA_IN_REG);
 	int_reg = spi_reg(orion_spi, ORION_SPI_INT_CAUSE_REG);
@@ -384,6 +391,11 @@ orion_spi_write_read_8bit(struct spi_device *spi,
 		writel(0, tx_reg);
 
 	if (orion_spi_wait_till_ready(orion_spi) < 0) {
+		if (cs_single_byte) {
+			orion_spi_set_cs(spi, 1);
+			/* Satisfy some SLIC devices requirements */
+			udelay(4);
+		}
 		dev_err(&spi->dev, "TXS timed out\n");
 		return -1;
 	}
@@ -391,6 +403,12 @@ orion_spi_write_read_8bit(struct spi_device *spi,
 	if (rx_buf && *rx_buf)
 		*(*rx_buf)++ = readl(rx_reg);
 
+	if (cs_single_byte) {
+		orion_spi_set_cs(spi, 1);
+		/* Satisfy some SLIC devices requirements */
+		udelay(4);
+	}
+
 	return 1;
 }
 
@@ -626,7 +644,7 @@ static int orion_spi_probe(struct platform_device *pdev)
 	}
 
 	/* we support all 4 SPI modes and LSB first option */
-	master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_LSB_FIRST;
+	master->mode_bits = SPI_CPHA | SPI_CPOL | SPI_LSB_FIRST | SPI_1BYTE_CS;
 	master->set_cs = orion_spi_set_cs;
 	master->transfer_one = orion_spi_transfer_one;
 	master->num_chipselect = ORION_NUM_CHIPSELECTS;
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 51d7c004fbab..998579807a04 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -1937,6 +1937,8 @@ static int of_spi_parse_dt(struct spi_controller *ctlr, struct spi_device *spi,
 		spi->mode |= SPI_LSB_FIRST;
 	if (of_property_read_bool(nc, "spi-cs-high"))
 		spi->mode |= SPI_CS_HIGH;
+	if (of_find_property(nc, "spi-1byte-cs", NULL))
+		spi->mode |= SPI_1BYTE_CS;
 
 	/* Device DUAL/QUAD mode */
 	if (!of_property_read_u32(nc, "spi-tx-bus-width", &value)) {
@@ -3419,15 +3421,15 @@ int spi_setup(struct spi_device *spi)
 		spi_set_thread_rt(spi->controller);
 	}
 
-	dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%u bits/w, %u Hz max --> %d\n",
+	dev_dbg(&spi->dev, "setup mode %d, %s%s%s%s%s%u bits/w, %u Hz max --> %d\n",
 			(int) (spi->mode & (SPI_CPOL | SPI_CPHA)),
 			(spi->mode & SPI_CS_HIGH) ? "cs_high, " : "",
 			(spi->mode & SPI_LSB_FIRST) ? "lsb, " : "",
 			(spi->mode & SPI_3WIRE) ? "3wire, " : "",
 			(spi->mode & SPI_LOOP) ? "loopback, " : "",
+			(spi->mode & SPI_1BYTE_CS) ? "single_cs_byte, " : "",
 			spi->bits_per_word, spi->max_speed_hz,
 			status);
-
 	return status;
 }
 EXPORT_SYMBOL_GPL(spi_setup);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index aa09fdc8042d..7f65ff6fc25d 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -186,6 +186,7 @@ struct spi_device {
 #define	SPI_TX_OCTAL	0x2000			/* transmit with 8 wires */
 #define	SPI_RX_OCTAL	0x4000			/* receive with 8 wires */
 #define	SPI_3WIRE_HIZ	0x8000			/* high impedance turnaround */
+#define	SPI_1BYTE_CS	0x10000			/* toggle cs after each byte */
 	int			irq;
 	void			*controller_state;
 	void			*controller_data;
-- 
2.17.1