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Date:	Thu, 22 May 2014 01:38:02 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>,
	Robert Richter <rric@...nel.org>,
	Daniel J Blueman <daniel@...ascale.com>,
	Andreas Herrmann <herrmann.der.user@...glemail.com>,
	linux-kernel@...r.kernel.org,
	Aravind Gopalakrishnan <Aravind.Gopalakrishnan@....com>,
	linux-pci@...r.kernel.org, Borislav Petkov <bp@...e.de>,
	Myron Stowe <myron.stowe@...hat.com>
Subject: Re: [PATCH V5 3/4] x86/PCI: Stop enabling ECS for AMD CPUs after
 Fam16h

On Wed, May 21, 2014 at 05:18:17PM -0600, Bjorn Helgaas wrote:
> ECS is an AMD mechanism that allows access to extended PCI config space
> (offsets 256-4096) via I/O ports CF8/CFCh.  We normally use ECAM, i.e.,
> MMCONFIG, to access that space, but apparently old machines have issues
> that meant we couldn't use ECAM.
> 
> The solution was to enable ECS so we could use configuration mechanism #1
> (I/O ports CF8/CFCh) to access extended config space.  See 831d991821da
> ("x86: add PCI extended config space access for AMD Barcelona").
> 
> New machines should be able to use ECAM, which means they don't need the
> CPU-specific code to enable ECS.  This patch leaves ECS the same on all
> existing platforms, but stops enabling it on platforms after Fam16h.
> 
> Those future platforms should be able to use the standard ACPI MCFG/_CBA
> descriptions of the PCIe ECAM mechanism.
> 
> Signed-off-by: Bjorn Helgaas <bhelgaas@...gle.com>
> CC: Robert Richter <rric@...nel.org>
> ---
>  arch/x86/pci/amd_bus.c |    4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/x86/pci/amd_bus.c b/arch/x86/pci/amd_bus.c
> index aa936e3a2019..67dadf179348 100644
> --- a/arch/x86/pci/amd_bus.c
> +++ b/arch/x86/pci/amd_bus.c
> @@ -405,7 +405,9 @@ static int __init amd_postcore_init(void)
>  		return 0;
>  
>  	early_fill_mp_bus_info();
> -	pci_io_ecs_init();
> +
> +	if (boot_cpu_data.x86 <= 0x16)

Fam 0x16, i.e. hex? I think we talked about fam 0x10, i.e. 16 decimal.

Oh well, that's an AMD call now.

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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