[Intel-wired-lan] [PATCH S37 04/15] ice: Don't allow same value for Rx tail to be written twice

Tony Nguyen anthony.l.nguyen at intel.com
Wed Jan 22 15:20:30 UTC 2020

From: Brett Creeley <brett.creeley at intel.com>

Currently we compare the value we are about to write to the Rx tail
register with the previous value of next_to_use. The problem with this
is we only write tail on 8 descriptor boundaries, but next_to_use is
updated whenever we clean Rx descriptors. Fix this by comparing the
value we are about to write to tail with the previously written tail
value. This will prevent duplicate Rx tail bumps.

Signed-off-by: Brett Creeley <brett.creeley at intel.com>
 drivers/net/ethernet/intel/ice/ice_txrx_lib.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
index 35bbc4ff603c..6da048a6ca7c 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx_lib.c
@@ -10,7 +10,7 @@
 void ice_release_rx_desc(struct ice_ring *rx_ring, u32 val)
-	u16 prev_ntu = rx_ring->next_to_use;
+	u16 prev_ntu = rx_ring->next_to_use & ~0x7;
 	rx_ring->next_to_use = val;

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