Re: bug in drivers/edac/mpc85xx_edac.c:mpc85xx_mc_check()

[Doug Thompson]

Dave, can you look at this

doug thompson

--- On Tue, 4/28/09, Jeff Haran <jharan@xxxxxxxxxxx> wrote:

> From: Jeff Haran <jharan@xxxxxxxxxxx>
> Subject: bug in drivers/edac/mpc85xx_edac.c:mpc85xx_mc_check()
> To: linux-kernel@xxxxxxxxxxxxxxx
> Date: Tuesday, April 28, 2009, 7:23 PM
> Hi,
> 
> Recent versions of this function contain the following
> snippets:
> 
>     if (err_detect & DDR_EDE_SBE)
>         edac_mc_handle_ce(mci, pfn,
> err_addr & PAGE_MASK,
>                
>   syndrome, row_index, 0, mci->ctl_name);
> 
>     if (err_detect & DDR_EDE_MBE)
>         edac_mc_handle_ue(mci, pfn,
> err_addr & PAGE_MASK,
>                
>   row_index, mci->ctl_name);
> 
> I am pretty sure the references to PAGE_MASK should be
> proceeded by a
> tilda, as in:
> 
>     if (err_detect & DDR_EDE_SBE)
>         edac_mc_handle_ce(mci, pfn,
> err_addr & ~PAGE_MASK,
>                
>   syndrome, row_index, 0, mci->ctl_name);
> 
>     if (err_detect & DDR_EDE_MBE)
>         edac_mc_handle_ue(mci, pfn,
> err_addr & ~PAGE_MASK,
>                
>   row_index, mci->ctl_name);
> 
> 
> Much as I would like to submit a tested patch like the rest
> of the
> world, I find myself in the situation where the only
> Freescale target
> system I have to test on is running a 3 year old kernel
> (2.6.14), which
> preceeds the introduction of EDAC driver support, at least
> for
> Freescale. So the best I can do is borrow from the new EDAC
> driver and
> backport it to the old kernel.
> 
> But I have learned a few things in this process and can
> thus share what
> I've learned as it may be of help to the EDAC driver
> developers:
> 
> 1) Before you read the Freescale 8548 CAPTURE_ADDRESS
> register, you want
> to read CAPTURE_ATTRIBUTES first and make sure the VLD bit
> (least
> significant bit in the register) is set or else the data
> in
> CAPTURE_ADDRESS may not be yet valid.
> 
> 2) When you are done scrubbing the memory with the single
> bit error, you
> want to write 0 to CAPTURE_ATTRIBUTES so as to clear VLD
> and thus setup
> the ECC capture logic to capture the next single bit
> error.
> 
> Please include this email address in responses as I do not
> subscribe.
> 
> Thanks,
> 
> Jeff Haran
> Brocade
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