net: qca_spi: Add available buffer space verification

Interferences on the SPI line could distort the response of
available buffer space. So at least we should check that the
response doesn't exceed the maximum available buffer space.
In error case increase a new error counter and retry it later.
This behavior avoids buffer errors in the QCA7000, which
results in an unnecessary chip reset including packet loss.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 15 insertions, 1 deletions

diff --git a/drivers/net/ethernet/qualcomm/qca_spi.c b/drivers/net/ethernet/qualcomm/qca_spi.c
index d5310504f436..97f92953bdb9 100644
--- a/drivers/net/ethernet/qualcomm/qca_spi.c
+++ b/drivers/net/ethernet/qualcomm/qca_spi.c
@@ -289,6 +289,14 @@ qcaspi_transmit(struct qcaspi *qca)
 
 	qcaspi_read_register(qca, SPI_REG_WRBUF_SPC_AVA, &available);
 
+	if (available > QCASPI_HW_BUF_LEN) {
+		/* This could only happen by interferences on the SPI line.
+		 * So retry later ...
+		 */
+		qca->stats.buf_avail_err++;
+		return -1;
+	}
+
 	while (qca->txr.skb[qca->txr.head]) {
 		pkt_len = qca->txr.skb[qca->txr.head]->len + QCASPI_HW_PKT_LEN;
 
@@ -355,7 +363,13 @@ qcaspi_receive(struct qcaspi *qca)
 	netdev_dbg(net_dev, "qcaspi_receive: SPI_REG_RDBUF_BYTE_AVA: Value: %08x\n",
 		   available);
 
-	if (available == 0) {
+	if (available > QCASPI_HW_BUF_LEN) {
+		/* This could only happen by interferences on the SPI line.
+		 * So retry later ...
+		 */
+		qca->stats.buf_avail_err++;
+		return -1;
+	} else if (available == 0) {
 		netdev_dbg(net_dev, "qcaspi_receive called without any data being available!\n");
 		return -1;
 	}