Re: NIU driver: Sun x8 Express Quad Gigabit Ethernet Adapter

Jesper Krogh
2008-11-12T17:56:57Z

David Miller wrote:
> I am guessing you're running a 32-bit x86 kernel.
>
> In such a case the driver has to define a local readq()
> and writeq() implementation.
>
> What I provide for NIU right now reads the upper 32-bits
> then the lower 32-bits of the register.
>
> Guess what that does? The packet counters live in the upper
> 32-bits and the MARK bits live in the lower 32-bits of the
> TX_CS register.
>
> So it first reads the packet counters, and as a side effect that
> clears the MARK bits in the TX_CS register. So when we read the lower
> 32-bits the MARK bits are always seen as zero.
>
> BzzaaarT!
>
> So the following patch should fix this bug. writeq() should
> be OK as-is, so doesn't need a similar change.
>
> diff --git a/drivers/net/niu.c b/drivers/net/niu.c
> index 9acb5d7..d8463b1 100644
> --- a/drivers/net/niu.c
> +++ b/drivers/net/niu.c
> @@ -51,8 +51,7 @@ MODULE_VERSION(DRV_MODULE_VERSION);
> #ifndef readq
> static u64 readq(void __iomem *reg)
> {
> - return (((u64)readl(reg + 0x4UL) << 32) |
> - (u64)readl(reg));
> + return ((u64) readl(reg)) | (((u64) readl(reg + 4UL)) << 32);
> }
>
> static void writeq(u64 val, void __iomem *reg)

On my system, I'm not in a position where I can just pull down the
server and test, but if the above seems plausible that it is the same
bug I hit using the 10GBitE card, then I'll definately try to test it out.

I sort-of reliably hit the problem after a few day of production on a 16
core, amd64 system running NFS-server.

Does it seem likely to be the same problem?

Thanks
--
Jesper Krogh