netdev - Re: [PATCH] e1000: Work around 82571 completion timout on Pseries HW

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Date:	Wed, 16 May 2007 12:00:57 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Auke Kok <auke-jan.h.kok@...el.com>
CC:	wenxiong@...ibm.com, e1000-devel@...ts.sourceforge.net,
	netdev@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH] e1000: Work around 82571 completion timout on Pseries
 HW

Auke Kok wrote:
> Our 82571 (first PCI-E hardware) causes P-Series hardware to throw
> issues. Disabling PCI-E completion timeouts in our NIC resolves
> the issue.
> 
> Signed-off-by: Auke Kok <auke-jan.h.kok@...el.com>
> Cc: Wen Xiong <wenxiong@...ibm.com>
> ---
> 
>  drivers/net/e1000/e1000_main.c |   10 ++++++++++
>  1 files changed, 10 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/net/e1000/e1000_main.c b/drivers/net/e1000/e1000_main.c
> index 49be393..830d851 100644
> --- a/drivers/net/e1000/e1000_main.c
> +++ b/drivers/net/e1000/e1000_main.c
> @@ -819,6 +819,16 @@ e1000_reset(struct e1000_adapter *adapter)
>  		E1000_WRITE_REG(&adapter->hw, CTRL, ctrl);
>  	}
>  
> +#if defined(CONFIG_PPC64) || defined(CONFIG_PPC)
> +#define E1000_GCR_DISABLE_TIMEOUT_MECHANISM 0x80000000
> +	if (adapter->hw.mac.type == e1000_82571) {
> +		/* work around pSeries hardware by disabling timeouts */
> +		u32 gcr = E1000_READ_REG(&adapter->hw, E1000_GCR);
> +		gcr |= E1000_GCR_DISABLE_TIMEOUT_MECHANISM;
> +		E1000_WRITE_REG(&adapter->hw, E1000_GCR, gcr);

Why is this needed?

Is pSeries PCI-E implementation problematic?  Or is this a e1000 PCI-E 
hardware bug?  If the former, I wonder if this is the best way to work 
around the issue, especially since it might crop up in other PCI-E 
boards besides e1000.  If the latter, it seems like we should disable 
the feature on all platforms.

	Jeff


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