[PATCH net 8/8] net: mscc: ocelot: report ndo_get_stats64 from the wraparound-resistant ocelot->stats

Vladimir Oltean
2022-08-16T13:55:07Z

Rather than reading the stats64 counters directly from the 32-bit
hardware, it's better to rely on the output produced by the periodic
ocelot_port_update_stats().

It would be even better to call ocelot_port_update_stats() right from
ocelot_get_stats64() to make sure we report the current values rather
than the ones from 2 seconds ago. But we need to export
ocelot_port_update_stats() from the switch lib towards the switchdev
driver for that, and future work will largely undo that.

There are more ocelot-based drivers waiting to be introduced, an example
of which is the SPI-controlled VSC7512. In that driver's case, it will
be impossible to call ocelot_port_update_stats() from ndo_get_stats64
context, since the latter is atomic, and reading the stats over SPI is
sleepable. So the compromise taken here, which will also hold going
forward, is to report 64-bit counters to stats64, which are not 100% up
to date.

Fixes: a556c76adc05 ("net: mscc: Add initial Ocelot switch support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
---
drivers/net/ethernet/mscc/ocelot_net.c | 53 +++++++++++++-------------
1 file changed, 26 insertions(+), 27 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot_net.c b/drivers/net/ethernet/mscc/ocelot_net.c
index 6b9d37138844..330d30841cdc 100644
--- a/drivers/net/ethernet/mscc/ocelot_net.c
+++ b/drivers/net/ethernet/mscc/ocelot_net.c
@@ -725,41 +725,40 @@ static void ocelot_get_stats64(struct net_device *dev,
struct ocelot_port_private *priv = netdev_priv(dev);
struct ocelot *ocelot = priv->port.ocelot;
int port = priv->port.index;
+ u64 *s;

spin_lock(&ocelot->stats_lock);

- /* Configure the port to read the stats from */
- ocelot_write(ocelot, SYS_STAT_CFG_STAT_VIEW(port),
- SYS_STAT_CFG);
+ s = &ocelot->stats[port * OCELOT_NUM_STATS];

/* Get Rx stats */
- stats->rx_bytes = ocelot_read(ocelot, SYS_COUNT_RX_OCTETS);
- stats->rx_packets = ocelot_read(ocelot, SYS_COUNT_RX_SHORTS) +
- ocelot_read(ocelot, SYS_COUNT_RX_FRAGMENTS) +
- ocelot_read(ocelot, SYS_COUNT_RX_JABBERS) +
- ocelot_read(ocelot, SYS_COUNT_RX_LONGS) +
- ocelot_read(ocelot, SYS_COUNT_RX_64) +
- ocelot_read(ocelot, SYS_COUNT_RX_65_127) +
- ocelot_read(ocelot, SYS_COUNT_RX_128_255) +
- ocelot_read(ocelot, SYS_COUNT_RX_256_511) +
- ocelot_read(ocelot, SYS_COUNT_RX_512_1023) +
- ocelot_read(ocelot, SYS_COUNT_RX_1024_1526) +
- ocelot_read(ocelot, SYS_COUNT_RX_1527_MAX);
- stats->multicast = ocelot_read(ocelot, SYS_COUNT_RX_MULTICAST);
+ stats->rx_bytes = s[OCELOT_STAT_RX_OCTETS];
+ stats->rx_packets = s[OCELOT_STAT_RX_SHORTS] +
+ s[OCELOT_STAT_RX_FRAGMENTS] +
+ s[OCELOT_STAT_RX_JABBERS] +
+ s[OCELOT_STAT_RX_LONGS] +
+ s[OCELOT_STAT_RX_64] +
+ s[OCELOT_STAT_RX_65_127] +
+ s[OCELOT_STAT_RX_128_255] +
+ s[OCELOT_STAT_RX_256_511] +
+ s[OCELOT_STAT_RX_512_1023] +
+ s[OCELOT_STAT_RX_1024_1526] +
+ s[OCELOT_STAT_RX_1527_MAX];
+ stats->multicast = s[OCELOT_STAT_RX_MULTICAST];
stats->rx_dropped = dev->stats.rx_dropped;

/* Get Tx stats */
- stats->tx_bytes = ocelot_read(ocelot, SYS_COUNT_TX_OCTETS);
- stats->tx_packets = ocelot_read(ocelot, SYS_COUNT_TX_64) +
- ocelot_read(ocelot, SYS_COUNT_TX_65_127) +
- ocelot_read(ocelot, SYS_COUNT_TX_128_255) +
- ocelot_read(ocelot, SYS_COUNT_TX_256_511) +
- ocelot_read(ocelot, SYS_COUNT_TX_512_1023) +
- ocelot_read(ocelot, SYS_COUNT_TX_1024_1526) +
- ocelot_read(ocelot, SYS_COUNT_TX_1527_MAX);
- stats->tx_dropped = ocelot_read(ocelot, SYS_COUNT_TX_DROPS) +
- ocelot_read(ocelot, SYS_COUNT_TX_AGING);
- stats->collisions = ocelot_read(ocelot, SYS_COUNT_TX_COLLISION);
+ stats->tx_bytes = s[OCELOT_STAT_TX_OCTETS];
+ stats->tx_packets = s[OCELOT_STAT_TX_64] +
+ s[OCELOT_STAT_TX_65_127] +
+ s[OCELOT_STAT_TX_128_255] +
+ s[OCELOT_STAT_TX_256_511] +
+ s[OCELOT_STAT_TX_512_1023] +
+ s[OCELOT_STAT_TX_1024_1526] +
+ s[OCELOT_STAT_TX_1527_MAX];
+ stats->tx_dropped = s[OCELOT_STAT_TX_DROPS] +
+ s[OCELOT_STAT_TX_AGED];
+ stats->collisions = s[OCELOT_STAT_TX_COLLISION];

spin_unlock(&ocelot->stats_lock);
}
--
2.34.1