netdev - Re: [PATCH v2 1/1] net:fec: fix WARNING caused by lack of calls to dma_mapping

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Date:	Thu, 14 Nov 2013 16:37:57 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	B38611@...escale.com
Cc:	bhutchings@...arflare.com, netdev@...r.kernel.org,
	stephen@...workplumber.org
Subject: Re: [PATCH v2 1/1] net:fec: fix WARNING caused by lack of calls to
 dma_mapping_error()

From: Fugang Duan <B38611@...escale.com>
Date: Thu, 14 Nov 2013 09:57:10 +0800

> The driver fails to check the results of DMA mapping and results in
> the following warning: (with kernel config "CONFIG_DMA_API_DEBUG" enable)
 ...
> Because dma-debug add new interfaces to debug dma mapping errors, pls refer
> to: http://lwn.net/Articles/516640/
> 
> After dma mapping, it must call dma_mapping_error() to check mapping error,
> otherwise the map_err_type alway is MAP_ERR_NOT_CHECKED, check_unmap() define
> the mapping is not checked and dump the error msg. So,add dma_mapping_error()
> checking to fix the WARNING
> 
> And RX DMA buffers are used repeatedly and the driver copies it into an skb,
> fec_enet_rx() should not map or unmap, use dma_sync_single_for_cpu()/dma_sync_single_for_device()
> instead of dma_map_single()/dma_unmap_single().
> 
> There have another potential issue:  fec_enet_rx() passes the DMA address to __va().
> Physical and DMA addresses are *not* the same thing. They may differ if the device
> is behind an IOMMU or bounce buffering was required, or just because there is a fixed
> offset between the device and host physical addresses. Also fix it in this patch.
> 
> =============================================
> V2: add net_ratelimit() to limit map err message.
>     use dma_sync_single_for_cpu() instead of dma_map_single().
>     fix the issue that pass DMA addresses to __va() to get virture address.
> V1: initial send
> =============================================
> 
> Signed-off-by: Fugang Duan <B38611@...escale.com>

Applied, thanks a lot.
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