From c24782e612dce377cf9149ad787998af7694f757 Mon Sep 17 00:00:00 2001 From: andrea merello Date: Tue, 18 Feb 2014 02:10:46 +0100 Subject: [PATCH] rtl818x: make sure TX descriptor writes are done before kicking DMA The TX descriptors are consumed by the HW using DMA. Even if in the driver code the TX descriptor writes appears before the HW "dma kick" register writes, the CPU may reorder them. If this happens, the TX may not happen at all becase the "valid" descriptor flag may have not been set yet. This patch adds a write memory barrier to ensures the TX descriptor is written before writing to the HW "dma kick" register. Signed-off-by: Andrea Merello Signed-off-by: John W. Linville --- drivers/net/wireless/rtl818x/rtl8180/dev.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/drivers/net/wireless/rtl818x/rtl8180/dev.c b/drivers/net/wireless/rtl818x/rtl8180/dev.c index 45d2cc14d71c..959e699702e8 100644 --- a/drivers/net/wireless/rtl818x/rtl8180/dev.c +++ b/drivers/net/wireless/rtl818x/rtl8180/dev.c @@ -341,6 +341,12 @@ static void rtl8180_tx(struct ieee80211_hw *dev, */ wmb(); entry->flags = cpu_to_le32(tx_flags); + /* We must be sure this has been written before followings HW + * register write, because this write will made the HW attempts + * to DMA the just-written data + */ + wmb(); + __skb_queue_tail(&ring->queue, skb); if (ring->entries - skb_queue_len(&ring->queue) < 2) ieee80211_stop_queue(dev, prio); -- 2.20.1