On Fri, 2013-06-21 at 17:58 +0200, Arnd Bergmann wrote:
> 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:
So it should be declared dma_addr_t then,
> + 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.
It still has a dependency on dma_addr_t size being 32 bit
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