linux-kernel - [PATCH 4.4 62/65] staging: iio: ad2s1210: Fix SPI reading

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Message-Id: <20200526183928.588655660@linuxfoundation.org>
Date:   Tue, 26 May 2020 20:53:21 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dragos Bogdan <dragos.bogdan@...log.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Stable@...r.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH 4.4 62/65] staging: iio: ad2s1210: Fix SPI reading

From: Dragos Bogdan <dragos.bogdan@...log.com>

commit 5e4f99a6b788047b0b8a7496c2e0c8f372f6edf2 upstream.

If the serial interface is used, the 8-bit address should be latched using
the rising edge of the WR/FSYNC signal.

This basically means that a CS change is required between the first byte
sent, and the second one.
This change splits the single-transfer transfer of 2 bytes into 2 transfers
with a single byte, and CS change in-between.

Note fixes tag is not accurate, but reflects a point beyond which there
are too many refactors to make backporting straight forward.

Fixes: b19e9ad5e2cb ("staging:iio:resolver:ad2s1210 general driver cleanup.")
Signed-off-by: Dragos Bogdan <dragos.bogdan@...log.com>
Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
Cc: <Stable@...r.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/staging/iio/resolver/ad2s1210.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -125,17 +125,24 @@ static int ad2s1210_config_write(struct
 static int ad2s1210_config_read(struct ad2s1210_state *st,
 		       unsigned char address)
 {
-	struct spi_transfer xfer = {
-		.len = 2,
-		.rx_buf = st->rx,
-		.tx_buf = st->tx,
+	struct spi_transfer xfers[] = {
+		{
+			.len = 1,
+			.rx_buf = &st->rx[0],
+			.tx_buf = &st->tx[0],
+			.cs_change = 1,
+		}, {
+			.len = 1,
+			.rx_buf = &st->rx[1],
+			.tx_buf = &st->tx[1],
+		},
 	};
 	int ret = 0;
 
 	ad2s1210_set_mode(MOD_CONFIG, st);
 	st->tx[0] = address | AD2S1210_MSB_IS_HIGH;
 	st->tx[1] = AD2S1210_REG_FAULT;
-	ret = spi_sync_transfer(st->sdev, &xfer, 1);
+	ret = spi_sync_transfer(st->sdev, xfers, 2);
 	if (ret < 0)
 		return ret;
 	st->old_data = true;