Merge branch 'qca_spi-sync'

Stefan Wahren says:

====================
net: qca_spi: Improve sync handling

This small patch series contains some improvements of the sync
handling. This was discovered while the QCA7000 was doing SLAC
(Signal Level Attenuation Characterization).
====================
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/qualcomm/qca_debug.c

@@ -62,6 +62,7 @@ static const char qcaspi_gstrings_stats[][ETH_GSTRING_LEN] = {
 	"SPI errors",
 	"Write verify errors",
 	"Buffer available errors",
+	"Bad signature",
 };
 
 #ifdef CONFIG_DEBUG_FS

drivers/net/ethernet/qualcomm/qca_spi.c

@@ -504,8 +504,12 @@ qcaspi_qca7k_sync(struct qcaspi *qca, int event)
 		qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
 		qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
 		if (signature != QCASPI_GOOD_SIGNATURE) {
+			if (qca->sync == QCASPI_SYNC_READY)
+				qca->stats.bad_signature++;
+
 			qca->sync = QCASPI_SYNC_UNKNOWN;
 			netdev_dbg(qca->net_dev, "sync: got CPU on, but signature was invalid, restart\n");
+			return;
 		} else {
 			/* ensure that the WRBUF is empty */
 			qcaspi_read_register(qca, SPI_REG_WRBUF_SPC_AVA,
@@ -523,10 +527,14 @@ qcaspi_qca7k_sync(struct qcaspi *qca, int event)
 
 	switch (qca->sync) {
 	case QCASPI_SYNC_READY:
-		/* Read signature, if not valid go to unknown state. */
+		/* Check signature twice, if not valid go to unknown state. */
 		qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
+		if (signature != QCASPI_GOOD_SIGNATURE)
+			qcaspi_read_register(qca, SPI_REG_SIGNATURE, &signature);
+
 		if (signature != QCASPI_GOOD_SIGNATURE) {
 			qca->sync = QCASPI_SYNC_UNKNOWN;
+			qca->stats.bad_signature++;
 			netdev_dbg(qca->net_dev, "sync: bad signature, restart\n");
 			/* don't reset right away */
 			return;

drivers/net/ethernet/qualcomm/qca_spi.h

@@ -75,6 +75,7 @@ struct qcaspi_stats {
 	u64 spi_err;
 	u64 write_verify_failed;
 	u64 buf_avail_err;
+	u64 bad_signature;
 };
 
 struct qcaspi {