net: qca_spi: Fix race condition in spi transfers

With performance optimization the spi transfer and messages of basic
register operations like qcaspi_read_register moved into the private
driver structure. But they weren't protected against mutual access
(e.g. between driver kthread and ethtool). So dumping the QCA7000
registers via ethtool during network traffic could make spi_sync
hang forever, because the completion in spi_message is overwritten.

So revert the optimization completely.

Fixes: 291ab06ecf676 ("net: qualcomm: new Ethernet over SPI driver for QCA700")
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 36 insertions, 40 deletions

diff --git a/drivers/net/ethernet/qualcomm/qca_7k.c b/drivers/net/ethernet/qualcomm/qca_7k.c
index ffe7a16bdfc8..6c8543fb90c0 100644
--- a/drivers/net/ethernet/qualcomm/qca_7k.c
+++ b/drivers/net/ethernet/qualcomm/qca_7k.c
@@ -45,34 +45,33 @@ qcaspi_read_register(struct qcaspi *qca, u16 reg, u16 *result)
 {
 	__be16 rx_data;
 	__be16 tx_data;
-	struct spi_transfer *transfer;
-	struct spi_message *msg;
+	struct spi_transfer transfer[2];
+	struct spi_message msg;
 	int ret;
 
+	memset(transfer, 0, sizeof(transfer));
+
+	spi_message_init(&msg);
+
 	tx_data = cpu_to_be16(QCA7K_SPI_READ | QCA7K_SPI_INTERNAL | reg);
+	*result = 0;
+
+	transfer[0].tx_buf = &tx_data;
+	transfer[0].len = QCASPI_CMD_LEN;
+	transfer[1].rx_buf = &rx_data;
+	transfer[1].len = QCASPI_CMD_LEN;
+
+	spi_message_add_tail(&transfer[0], &msg);
 
 	if (qca->legacy_mode) {
-		msg = &qca->spi_msg1;
-		transfer = &qca->spi_xfer1;
-		transfer->tx_buf = &tx_data;
-		transfer->rx_buf = NULL;
-		transfer->len = QCASPI_CMD_LEN;
-		spi_sync(qca->spi_dev, msg);
-	} else {
-		msg = &qca->spi_msg2;
-		transfer = &qca->spi_xfer2[0];
-		transfer->tx_buf = &tx_data;
-		transfer->rx_buf = NULL;
-		transfer->len = QCASPI_CMD_LEN;
-		transfer = &qca->spi_xfer2[1];
+		spi_sync(qca->spi_dev, &msg);
+		spi_message_init(&msg);
 	}
-	transfer->tx_buf = NULL;
-	transfer->rx_buf = &rx_data;
-	transfer->len = QCASPI_CMD_LEN;
-	ret = spi_sync(qca->spi_dev, msg);
+	spi_message_add_tail(&transfer[1], &msg);
+	ret = spi_sync(qca->spi_dev, &msg);
 
 	if (!ret)
-		ret = msg->status;
+		ret = msg.status;
 
 	if (ret)
 		qcaspi_spi_error(qca);
@@ -86,35 +85,32 @@ int
 qcaspi_write_register(struct qcaspi *qca, u16 reg, u16 value)
 {
 	__be16 tx_data[2];
-	struct spi_transfer *transfer;
-	struct spi_message *msg;
+	struct spi_transfer transfer[2];
+	struct spi_message msg;
 	int ret;
 
+	memset(&transfer, 0, sizeof(transfer));
+
+	spi_message_init(&msg);
+
 	tx_data[0] = cpu_to_be16(QCA7K_SPI_WRITE | QCA7K_SPI_INTERNAL | reg);
 	tx_data[1] = cpu_to_be16(value);
 
+	transfer[0].tx_buf = &tx_data[0];
+	transfer[0].len = QCASPI_CMD_LEN;
+	transfer[1].tx_buf = &tx_data[1];
+	transfer[1].len = QCASPI_CMD_LEN;
+
+	spi_message_add_tail(&transfer[0], &msg);
 	if (qca->legacy_mode) {
-		msg = &qca->spi_msg1;
-		transfer = &qca->spi_xfer1;
-		transfer->tx_buf = &tx_data[0];
-		transfer->rx_buf = NULL;
-		transfer->len = QCASPI_CMD_LEN;
-		spi_sync(qca->spi_dev, msg);
-	} else {
-		msg = &qca->spi_msg2;
-		transfer = &qca->spi_xfer2[0];
-		transfer->tx_buf = &tx_data[0];
-		transfer->rx_buf = NULL;
-		transfer->len = QCASPI_CMD_LEN;
-		transfer = &qca->spi_xfer2[1];
+		spi_sync(qca->spi_dev, &msg);
+		spi_message_init(&msg);
 	}
-	transfer->tx_buf = &tx_data[1];
-	transfer->rx_buf = NULL;
-	transfer->len = QCASPI_CMD_LEN;
-	ret = spi_sync(qca->spi_dev, msg);
+	spi_message_add_tail(&transfer[1], &msg);
+	ret = spi_sync(qca->spi_dev, &msg);
 
 	if (!ret)
-		ret = msg->status;
+		ret = msg.status;
 
 	if (ret)
 		qcaspi_spi_error(qca);