linux-kernel - Re: bug in drivers/edac/mpc85xx_edac.c:mpc85xx_mc

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Date:	Fri, 10 Apr 2009 14:47:15 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Jeff Haran" <jharan@...cade.COM>
Cc:	linux-kernel@...r.kernel.org,
	Doug Thompson <dougthompson@...ssion.com>,
	Kumar Gala <galak@...nel.crashing.org>,
	Dave Jiang <djiang@...sta.com>, linuxppc-dev@...abs.org
Subject: Re: bug in drivers/edac/mpc85xx_edac.c:mpc85xx_mc_check() ?

(cc's added)

On Wed, 8 Apr 2009 14:57:42 -0700
"Jeff Haran" <jharan@...cade.COM> wrote:

> Hi,
> 
> Recent versions of this function start off with:
> 
> static void mpc85xx_mc_check(struct mem_ctl_info *mci)
> {
>     struct mpc85xx_mc_pdata *pdata = mci->pvt_info;
>     ...
> 
>     err_detect = in_be32(pdata->mc_vbase + MPC85XX_MC_ERR_DETECT);
>     if (err_detect)
>         return;
> 
>     ...
> }
> 
> My reading of the Freescale 8548E Manual leads me to conclude that the
> Memory Error Detect register (ERR_DETECT) will have various bits set if
> the memory controller has detected an error since the last time it was
> cleared. If no memory error has occurred, the register will contain 0.
> 
> Perhaps I am missing something very basic, but it seem to me that the
> above "if" should be:
> 
>     if (!err_detect)
>         return;
> 
> as the existing code would seem to read "if any errors have occurred,
> ignore them", though perhaps testing has demonstrated that the Freescale
> manual is in error.
> 
> Please include this email address in responses as I do not subscribe.
> 
> Thanks,
> 
> Jeff Haran
> Brocade

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