qed: Fix reading wrong value in loop condition

[ Upstream commit ed4eac20 ]

The value of "sb_index" is written by the hardware. Reading its value and
writing it to "index" must finish before checking the loop condition.
Signed-off-by: Denis Bolotin <denis.bolotin@cavium.com>
Signed-off-by: Michal Kalderon <michal.kalderon@cavium.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>

drivers/net/ethernet/qlogic/qed/qed_int.c

@@ -992,6 +992,8 @@ static int qed_int_attentions(struct qed_hwfn *p_hwfn)
 	 */
 	do {
 		index = p_sb_attn->sb_index;
+		/* finish reading index before the loop condition */
+		dma_rmb();
 		attn_bits = le32_to_cpu(p_sb_attn->atten_bits);
 		attn_acks = le32_to_cpu(p_sb_attn->atten_ack);
 	} while (index != p_sb_attn->sb_index);