linux-kernel - Re: [PATCH] x86, quirks: Add workaround for AMD F16h Erratum792

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Date:	Mon, 20 Jan 2014 08:07:24 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
Cc:	tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
	x86@...nel.org, bp@...e.de, linux-kernel@...r.kernel.org,
	sherry.hurwitz@....com, hmh@....eng.br, Kim.Naru@....com,
	Suravee.Suthikulpanit@....com
Subject: Re: [PATCH] x86, quirks: Add workaround for AMD F16h Erratum792


* Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com> wrote:

> The workaround for this Erratum is included in AGESA. But BIOSes spun
> only after Jan2014 will have the fix (atleast server versions of the
> chip). The erratum affects both client and server platforms and since
> we cannot say with certainity that ALL BIOSes on systems out in the
> field will have the fix, we should probably insulate ourselves in case
> BIOS does not do the right thing or someone is using old BIOSes.
> 
> Refer Revision Guide for AMD F16h models 00h-0fh, document 51810
> Rev. 3.04, November2013 for details on the Erratum.
> 
> Tested the patch on Fam16h server platform and works fine.
> 
> Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>
> ---
>  arch/x86/kernel/quirks.c |   31 +++++++++++++++++++++++++++++++
>  1 file changed, 31 insertions(+)
> 
> diff --git a/arch/x86/kernel/quirks.c b/arch/x86/kernel/quirks.c
> index 04ee1e2..e55ae02 100644
> --- a/arch/x86/kernel/quirks.c
> +++ b/arch/x86/kernel/quirks.c
> @@ -571,3 +571,34 @@ DECLARE_PCI_FIXUP_FINAL(PCI_VENDOR_ID_AMD, PCI_DEVICE_ID_AMD_15H_NB_F5,
>  			quirk_amd_nb_node);
>  
>  #endif
> +
> +#if defined(CONFIG_PCI)
> +/*
> + * Apply AMD Fam16h Erratum792
> + * see Revision Guide for AMD F16h models 00h-0fh,
> + * document 51810 rev. 3.04, Nov 2013
> + */
> +static void quirk_amd_dram_scrub(struct pci_dev *dev)

The reference to the erratum is useful for people who want to see more 
details, but at least a short description of the problem being fixed 
and systems affected by the quirk is needed. 'DRAM scrub' is not very 
informative.

Thanks,

	Ingo
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