net: qca_spi: Introduce stat about bad signature

In order to identify significant signature issues add a new stat counter,
which increases on bad signature values that causes a sync loss.
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
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

@@ -504,6 +504,9 @@ 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;
@@ -531,6 +534,7 @@ qcaspi_qca7k_sync(struct qcaspi *qca, int event)
 
 		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 {