[PATCH net 08/13] net: stmmac: Fix Rx IC bit setting procedure for Rx-mitigation

[Serge Semin]

The WDT-less Rx-traffic mitigation is simple: enable the Rx-descriptor
Completion interrupt only when a particular number of descriptors handled
by the NIC. Alas it's broken now because the data variable rx_count_frames
is always set to zero due to commit 6fa9d691b91a ("net: stmmac: Prevent
divide-by-zero") (++rx_count_frames + rx_coal_frames > rx_coal_frames
always if no overflow happens). So Rx IC will be enabled for each
descriptor as soon as rx_coal_frames is non-zero or there is no Rx WDT
available, which basically disables the Rx-mitigation in the framework of
the number of received frames part. Fix that by discarding the statement:
rx_q->rx_count_frames += priv->rx_coal_frames.

Fixes: 6fa9d691b91a ("net: stmmac: Prevent divide-by-zero")
Signed-off-by: Serge Semin <Sergey.Semin at baikalelectronics.ru>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 229f827d7572..32aa7953d296 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -4627,7 +4627,6 @@ static inline void stmmac_rx_refill(struct stmmac_priv *priv, u32 queue)
 		stmmac_refill_desc3(priv, rx_q, p);
 
 		rx_q->rx_count_frames++;
-		rx_q->rx_count_frames += priv->rx_coal_frames[queue];
 		if (rx_q->rx_count_frames > priv->rx_coal_frames[queue])
 			rx_q->rx_count_frames = 0;
 
@@ -4967,7 +4966,6 @@ static bool stmmac_rx_refill_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
 		stmmac_refill_desc3(priv, rx_q, rx_desc);
 
 		rx_q->rx_count_frames++;
-		rx_q->rx_count_frames += priv->rx_coal_frames[queue];
 		if (rx_q->rx_count_frames > priv->rx_coal_frames[queue])
 			rx_q->rx_count_frames = 0;
 
-- 
2.39.2