Return-path: Received: from mail-wi0-f178.google.com ([209.85.212.178]:36780 "EHLO mail-wi0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932620AbbDUVd1 (ORCPT ); Tue, 21 Apr 2015 17:33:27 -0400 From: Malcolm Priestley To: gregkh@linuxfoundation.org Cc: linux-wireless@vger.kernel.org, Malcolm Priestley , Subject: [PATCH 1/3] staging: vt6655: vnt_tx_packet Correct TX order of OWNED_BY_NIC Date: Tue, 21 Apr 2015 22:33:00 +0100 Message-Id: <1429651982-4352-1-git-send-email-tvboxspy@gmail.com> (sfid-20150421_233331_626806_204D7E51) Sender: linux-wireless-owner@vger.kernel.org List-ID: The state of m_td0TD0.f1Owner should change after the buff_addr has been filled otherwise the device grabs the buffer too early. m_td0TD0.f1Owner is protected by memory barriers on both sides of change. iTDUsed is best incremented after MACvTransmit. It appears that f1Owner actually polls to do the memory transfer. A back port patch will be needed for v3.19 Signed-off-by: Malcolm Priestley Cc: # v4.0+ --- drivers/staging/vt6655/device_main.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-) diff --git a/drivers/staging/vt6655/device_main.c b/drivers/staging/vt6655/device_main.c index c5f8233..ed90b6f 100644 --- a/drivers/staging/vt6655/device_main.c +++ b/drivers/staging/vt6655/device_main.c @@ -1201,14 +1201,6 @@ static int vnt_tx_packet(struct vnt_private *priv, struct sk_buff *skb) if (dma_idx == TYPE_AC0DMA) head_td->pTDInfo->byFlags = TD_FLAGS_NETIF_SKB; - priv->iTDUsed[dma_idx]++; - - /* Take ownership */ - wmb(); - head_td->m_td0TD0.f1Owner = OWNED_BY_NIC; - - /* get Next */ - wmb(); priv->apCurrTD[dma_idx] = head_td->next; spin_unlock_irqrestore(&priv->lock, flags); @@ -1229,11 +1221,18 @@ static int vnt_tx_packet(struct vnt_private *priv, struct sk_buff *skb) head_td->buff_addr = cpu_to_le32(head_td->pTDInfo->skb_dma); + /* Poll Transmit the adapter */ + wmb(); + head_td->m_td0TD0.f1Owner = OWNED_BY_NIC; + wmb(); /* second memory barrier */ + if (head_td->pTDInfo->byFlags & TD_FLAGS_NETIF_SKB) MACvTransmitAC0(priv->PortOffset); else MACvTransmit0(priv->PortOffset); + priv->iTDUsed[dma_idx]++; + spin_unlock_irqrestore(&priv->lock, flags); return 0; -- 2.1.4