[PATCH 2/2] spi: spi-ti-qspi: Handle truncated frames properly

[Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>]

We clamp frame_length to a maximum of 4096, but do not limit the
number of words written or read properly.  This causes 4K reads (which
some m25p80-like flash chips support) to return garbage for the last
few bytes.

Recalculate the length of each transfer, taking the frame length into
account.  Use this length in qspi_{read,write}_msg(), and to increment
spi_message::actual_length.

Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Ben Hutchings <ben.hutchings@xxxxxxxxxxxxxxx>
---
 drivers/spi/spi-ti-qspi.c | 32 ++++++++++++++++++++------------
 1 file changed, 20 insertions(+), 12 deletions(-)

diff --git a/drivers/spi/spi-ti-qspi.c b/drivers/spi/spi-ti-qspi.c
index e5cefaca0589..4c0acee7a55f 100644
--- a/drivers/spi/spi-ti-qspi.c
+++ b/drivers/spi/spi-ti-qspi.c
@@ -225,16 +225,16 @@ static inline int ti_qspi_poll_wc(struct ti_qspi *qspi)
 	return  -ETIMEDOUT;
 }
 
-static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t,
+			  int count)
 {
-	int wlen, count, xfer_len;
+	int wlen, xfer_len;
 	unsigned int cmd;
 	const u8 *txbuf;
 	u32 data;
 
 	txbuf = t->tx_buf;
 	cmd = qspi->cmd | QSPI_WR_SNGL;
-	count = t->len;
 	wlen = t->bits_per_word >> 3;	/* in bytes */
 	xfer_len = wlen;
 
@@ -294,9 +294,10 @@ static int qspi_write_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 	return 0;
 }
 
-static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t,
+			 int count)
 {
-	int wlen, count;
+	int wlen;
 	unsigned int cmd;
 	u8 *rxbuf;
 
@@ -313,7 +314,6 @@ static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 		cmd |= QSPI_RD_SNGL;
 		break;
 	}
-	count = t->len;
 	wlen = t->bits_per_word >> 3;	/* in bytes */
 
 	while (count) {
@@ -344,12 +344,13 @@ static int qspi_read_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 	return 0;
 }
 
-static int qspi_transfer_msg(struct ti_qspi *qspi, struct spi_transfer *t)
+static int qspi_transfer_msg(struct ti_qspi *qspi, struct spi_transfer *t,
+			     int count)
 {
 	int ret;
 
 	if (t->tx_buf) {
-		ret = qspi_write_msg(qspi, t);
+		ret = qspi_write_msg(qspi, t, count);
 		if (ret) {
 			dev_dbg(qspi->dev, "Error while writing\n");
 			return ret;
@@ -357,7 +358,7 @@ static int qspi_transfer_msg(struct ti_qspi *qspi, struct spi_transfer *t)
 	}
 
 	if (t->rx_buf) {
-		ret = qspi_read_msg(qspi, t);
+		ret = qspi_read_msg(qspi, t, count);
 		if (ret) {
 			dev_dbg(qspi->dev, "Error while reading\n");
 			return ret;
@@ -374,7 +375,8 @@ static int ti_qspi_start_transfer_one(struct spi_master *master,
 	struct spi_device *spi = m->spi;
 	struct spi_transfer *t;
 	int status = 0, ret;
-	unsigned int frame_length;
+	unsigned int frame_length, transfer_length;
+	int wlen;
 
 	/* setup device control reg */
 	qspi->dc = 0;
@@ -404,14 +406,20 @@ static int ti_qspi_start_transfer_one(struct spi_master *master,
 		qspi->cmd = ((qspi->cmd & ~QSPI_WLEN_MASK) |
 			     QSPI_WLEN(t->bits_per_word));
 
-		ret = qspi_transfer_msg(qspi, t);
+		wlen = t->bits_per_word >> 3;
+		transfer_length = min(t->len / wlen, frame_length);
+
+		ret = qspi_transfer_msg(qspi, t, transfer_length * wlen);
 		if (ret) {
 			dev_dbg(qspi->dev, "transfer message failed\n");
 			mutex_unlock(&qspi->list_lock);
 			return -EINVAL;
 		}
 
-		m->actual_length += t->len;
+		m->actual_length += transfer_length * wlen;
+		frame_length -= transfer_length;
+		if (frame_length == 0)
+			break;
 	}
 
 	mutex_unlock(&qspi->list_lock);
-- 
2.8.0.rc3


-- 
Ben Hutchings
Software Developer, Codethink Ltd.


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