Merge branch 'topic/3wire-gpio' of...

Merge branch 'topic/3wire-gpio' of https://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi into spi-4.21 mode conflict

drivers/spi/spi-gpio.c

@@ -256,11 +256,29 @@ static int spi_gpio_setup(struct spi_device *spi)
 static int spi_gpio_set_direction(struct spi_device *spi, bool output)
 {
 	struct spi_gpio *spi_gpio = spi_to_spi_gpio(spi);
+	int ret;
 
 	if (output)
 		return gpiod_direction_output(spi_gpio->mosi, 1);
-	else
-		return gpiod_direction_input(spi_gpio->mosi);
+
+	ret = gpiod_direction_input(spi_gpio->mosi);
+	if (ret)
+		return ret;
+	/*
+	 * Send a turnaround high impedance cycle when switching
+	 * from output to input. Theoretically there should be
+	 * a clock delay here, but as has been noted above, the
+	 * nsec delay function for bit-banged GPIO is simply
+	 * {} because bit-banging just doesn't get fast enough
+	 * anyway.
+	 */
+	if (spi->mode & SPI_3WIRE_HIZ) {
+		gpiod_set_value_cansleep(spi_gpio->sck,
+					 !(spi->mode & SPI_CPOL));
+		gpiod_set_value_cansleep(spi_gpio->sck,
+					 !!(spi->mode & SPI_CPOL));
+	}
+	return 0;
 }
 
 static void spi_gpio_cleanup(struct spi_device *spi)
@@ -410,7 +428,7 @@ static int spi_gpio_probe(struct platform_device *pdev)
 		return status;
 
 	master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 32);
-	master->mode_bits = SPI_3WIRE | SPI_CPHA | SPI_CPOL;
+	master->mode_bits = SPI_3WIRE | SPI_3WIRE_HIZ | SPI_CPHA | SPI_CPOL;
 	master->flags = master_flags;
 	master->bus_num = pdev->id;
 	/* The master needs to think there is a chipselect even if not connected */

include/linux/spi/spi.h

@@ -157,6 +157,7 @@ struct spi_device {
 #define	SPI_CS_WORD	0x1000			/* toggle cs after each word */
 #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 */
 	int			irq;
 	void			*controller_state;
 	void			*controller_data;