1 files changed, 24 insertions, 16 deletions

diff --git a/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c b/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
index d298d780220d..326deb3177b6 100644
--- a/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
+++ b/drivers/gpu/drm/panel/panel-samsung-s6e63m0-spi.c
@@ -13,28 +13,28 @@
 
 static int s6e63m0_spi_dcs_read(struct device *dev, const u8 cmd, u8 *data)
 {
-	/*
-	 * FIXME: implement reading DCS commands over SPI so we can
-	 * properly identify which physical panel is connected.
-	 */
-	*data = 0;
+	struct spi_device *spi = to_spi_device(dev);
+	u16 buf[1];
+	u16 rbuf[1];
+	int ret;
+
+	/* SPI buffers are always in CPU order */
+	buf[0] = (u16)cmd;
+	ret = spi_write_then_read(spi, buf, 2, rbuf, 2);
+	dev_dbg(dev, "READ CMD: %04x RET: %04x\n", buf[0], rbuf[0]);
+	if (!ret)
+		/* These high 8 bits of the 9 contains the readout */
+		*data = (rbuf[0] & 0x1ff) >> 1;
 
-	return 0;
+	return ret;
 }
 
 static int s6e63m0_spi_write_word(struct device *dev, u16 data)
 {
 	struct spi_device *spi = to_spi_device(dev);
-	struct spi_transfer xfer = {
-		.len	= 2,
-		.tx_buf = &data,
-	};
-	struct spi_message msg;
-
-	spi_message_init(&msg);
-	spi_message_add_tail(&xfer, &msg);
 
-	return spi_sync(spi, &msg);
+	/* SPI buffers are always in CPU order */
+	return spi_write(spi, &data, 2);
 }
 
 static int s6e63m0_spi_dcs_write(struct device *dev, const u8 *data, size_t len)
@@ -42,10 +42,17 @@ static int s6e63m0_spi_dcs_write(struct device *dev, const u8 *data, size_t len)
 	int ret = 0;
 
 	dev_dbg(dev, "SPI writing dcs seq: %*ph\n", (int)len, data);
+
+	/*
+	 * This sends 9 bits with the first bit (bit 8) set to 0
+	 * This indicates that this is a command. Anything after the
+	 * command is data.
+	 */
 	ret = s6e63m0_spi_write_word(dev, *data);
 
 	while (!ret && --len) {
 		++data;
+		/* This sends 9 bits with the first bit (bit 8) set to 1 */
 		ret = s6e63m0_spi_write_word(dev, *data | DATA_MASK);
 	}
 
@@ -65,7 +72,8 @@ static int s6e63m0_spi_probe(struct spi_device *spi)
 	int ret;
 
 	spi->bits_per_word = 9;
-	spi->mode = SPI_MODE_3;
+	/* Preserve e.g. SPI_3WIRE setting */
+	spi->mode |= SPI_MODE_3;
 	ret = spi_setup(spi);
 	if (ret < 0) {
 		dev_err(dev, "spi setup failed.\n");