[PATCH 5.8 107/124] net: mscc: ocelot: divide watermark value by 60 when writing to SYS_ATOP

[Greg Kroah-Hartman]

From: Vladimir Oltean <vladimir.oltean@xxxxxxx>

[ Upstream commit 601e984f23abcaa7cf3eb078c13de4db3cf6a4f0 ]

Tail dropping is enabled for a port when:

1. A source port consumes more packet buffers than the watermark encoded
   in SYS:PORT:ATOP_CFG.ATOP.

AND

2. Total memory use exceeds the consumption watermark encoded in
   SYS:PAUSE_CFG:ATOP_TOT_CFG.

The unit of these watermarks is a 60 byte memory cell. That unit is
programmed properly into ATOP_TOT_CFG, but not into ATOP. Actually when
written into ATOP, it would get truncated and wrap around.

Fixes: a556c76adc05 ("net: mscc: Add initial Ocelot switch support")
Signed-off-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/net/ethernet/mscc/ocelot.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/net/ethernet/mscc/ocelot.c b/drivers/net/ethernet/mscc/ocelot.c
index 1438839e3f6ea..61bbb7a090042 100644
--- a/drivers/net/ethernet/mscc/ocelot.c
+++ b/drivers/net/ethernet/mscc/ocelot.c
@@ -2001,7 +2001,7 @@ void ocelot_port_set_maxlen(struct ocelot *ocelot, int port, size_t sdu)
 	struct ocelot_port *ocelot_port = ocelot->ports[port];
 	int maxlen = sdu + ETH_HLEN + ETH_FCS_LEN;
 	int pause_start, pause_stop;
-	int atop_wm;
+	int atop, atop_tot;
 
 	if (port == ocelot->npi) {
 		maxlen += OCELOT_TAG_LEN;
@@ -2022,12 +2022,12 @@ void ocelot_port_set_maxlen(struct ocelot *ocelot, int port, size_t sdu)
 	ocelot_rmw_rix(ocelot, SYS_PAUSE_CFG_PAUSE_STOP(pause_stop),
 		       SYS_PAUSE_CFG_PAUSE_STOP_M, SYS_PAUSE_CFG, port);
 
-	/* Tail dropping watermark */
-	atop_wm = (ocelot->shared_queue_sz - 9 * maxlen) /
+	/* Tail dropping watermarks */
+	atop_tot = (ocelot->shared_queue_sz - 9 * maxlen) /
 		   OCELOT_BUFFER_CELL_SZ;
-	ocelot_write_rix(ocelot, ocelot->ops->wm_enc(9 * maxlen),
-			 SYS_ATOP, port);
-	ocelot_write(ocelot, ocelot->ops->wm_enc(atop_wm), SYS_ATOP_TOT_CFG);
+	atop = (9 * maxlen) / OCELOT_BUFFER_CELL_SZ;
+	ocelot_write_rix(ocelot, ocelot->ops->wm_enc(atop), SYS_ATOP, port);
+	ocelot_write(ocelot, ocelot->ops->wm_enc(atop_tot), SYS_ATOP_TOT_CFG);
 }
 EXPORT_SYMBOL(ocelot_port_set_maxlen);
 
-- 
2.25.1