Return-path: Received: from mail-vx0-f174.google.com ([209.85.220.174]:33078 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754239Ab1BKBgD (ORCPT ); Thu, 10 Feb 2011 20:36:03 -0500 Received: by vxb37 with SMTP id 37so1073234vxb.19 for ; Thu, 10 Feb 2011 17:36:02 -0800 (PST) Message-ID: <4D5492BC.4030104@lwfinger.net> Date: Thu, 10 Feb 2011 19:37:00 -0600 From: Larry Finger MIME-Version: 1.0 To: Christian Lamparter CC: linux-wireless@vger.kernel.org, linville@tuxdriver.com Subject: Re: [PATCH for-2.6.38] p54pci: update receive dma buffers before and after processing References: <201102110148.43155.chunkeey@googlemail.com> In-Reply-To: <201102110148.43155.chunkeey@googlemail.com> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 02/10/2011 06:48 PM, Christian Lamparter wrote: > Documentation/DMA-API-HOWTO.txt states: > > "DMA transfers need to be synced properly in order for > the cpu and device to see the most uptodate and correct > copy of the DMA buffer." > > Cc: > Signed-off-by: Christian Lamparter > --- > Embarrassingly, this bug is unique to p54 and has been around > since 2.6.25. This tells us something interesting about our > userbase. I do use it on a LE system that probably has coherent DMA. Did someone run into this bug? > --- > diff --git a/drivers/net/wireless/p54/p54pci.c b/drivers/net/wireless/p54/p54pci.c > index 1eacba4..0494d7b 100644 > --- a/drivers/net/wireless/p54/p54pci.c > +++ b/drivers/net/wireless/p54/p54pci.c > @@ -199,6 +199,7 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index, > while (i != idx) { > u16 len; > struct sk_buff *skb; > + dma_addr_t dma_addr; > desc = &ring[i]; > len = le16_to_cpu(desc->len); > skb = rx_buf[i]; > @@ -216,17 +217,20 @@ static void p54p_check_rx_ring(struct ieee80211_hw *dev, u32 *index, > > len = priv->common.rx_mtu; > } > + dma_addr = le32_to_cpu(desc->host_addr); > + pci_dma_sync_single_for_cpu(priv->pdev, dma_addr, > + priv->common.rx_mtu + 32, PCI_DMA_FROMDEVICE); > skb_put(skb, len); > > if (p54_rx(dev, skb)) { > - pci_unmap_single(priv->pdev, > - le32_to_cpu(desc->host_addr), > - priv->common.rx_mtu + 32, > - PCI_DMA_FROMDEVICE); > + pci_unmap_single(priv->pdev, dma_addr, > + priv->common.rx_mtu + 32, PCI_DMA_FROMDEVICE); > rx_buf[i] = NULL; > - desc->host_addr = 0; > + desc->host_addr = cpu_to_le32(0); How does a BE zero differ from a LE zero? Using it this way emphasizes that it needs to be translated - I'm not objecting, just curious. Larry