Messages in this thread | | | From | Arnd Bergmann <> | Subject | Re: [PATCH v7] ethernet/arc/arc_emac - Add new driver | Date | Fri, 21 Jun 2013 17:58:25 +0200 |
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On Friday 21 June 2013, Joe Perches wrote: > On Fri, 2013-06-21 at 10:53 +0000, Alexey Brodkin wrote: > > On 06/21/2013 02:32 PM, Joe Perches wrote: > > > On Fri, 2013-06-21 at 11:20 +0400, Alexey Brodkin wrote: > > >> Driver for non-standard on-chip ethernet device ARC EMAC 10/100, > > >> instantiated in some legacy ARC (Synopsys) FPGA Boards such as > > >> ARCAngel4/ML50x. > [] > > >> + rxbd->data = (unsigned char *)cpu_to_le32(rx_buff->skb->data); > > > > > > 32 bit only. Should the Kconfig block have some arch_arc dependency > > > so it can't get compiled for 64 bit systems? > [] > > So for now I may easily add dependency on ARC if it makes acceptance of > > driver easier. > > I don't think it's a big problem. > > Maybe add a Kconfig "depends on !64BIT". > > Another thing to do would be to run it through sparse > with make C=1
No, I think the driver should just be made 64-bit clean. Not because anyone is going to need that of course, but to avoid having to add silly dependencies.
The problem is that rxbd->data is the wrong type. It is declared as a void*, but it is not a kernel pointer at all, it is a DMA pointer. Look at this code in context:
+ addr = dma_map_single(&ndev->dev, (void *)rx_buff->skb->data, + buflen, DMA_FROM_DEVICE); + if (dma_mapping_error(&ndev->dev, addr)) { + if (net_ratelimit()) + netdev_err(ndev, "cannot dma map\n"); + dev_kfree_skb(rx_buff->skb); + stats->rx_errors++; + continue; + } + dma_unmap_addr_set(&rx_buff, mapping, addr); + dma_unmap_len_set(&rx_buff, len, buflen); + + rxbd->data = (unsigned char *)cpu_to_le32(rx_buff->skb->data);
the 'addr' returned by dma_map_single is what the device really needs, although it is the same as rx_buff->skb->data with the trivial definition of dma_map_single.
The last line here needs to be
rxbd->data = cpu_to_le32(addr);
which fixes the bug, and has no dependency on a 32 bit CPU.
Arnd
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