netdev - Re: [PATCH 1/2] netdev: octeon_mgmt: Correct tx IFG workaround.

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Date:	Wed, 19 Jun 2013 18:37:19 -0700
From:	Joe Perches <joe@...ches.com>
To:	David Daney <ddaney.cavm@...il.com>
Cc:	netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
	linux-mips@...ux-mips.org, David Daney <david.daney@...ium.com>
Subject: Re: [PATCH 1/2] netdev: octeon_mgmt: Correct tx IFG workaround.

On Wed, 2013-06-19 at 18:28 -0700, David Daney wrote:
> On 06/19/2013 06:08 PM, Joe Perches wrote:
> > On Wed, 2013-06-19 at 17:40 -0700, David Daney wrote:
> >> From: David Daney <david.daney@...ium.com>
> >>
> >> The previous fix was still too agressive to meet ieee specs.  Increase
> >> to (14, 10).
> > []
> >> diff --git a/drivers/net/ethernet/octeon/octeon_mgmt.c b/drivers/net/ethernet/octeon/octeon_mgmt.c
> > []
> >> @@ -1141,10 +1141,13 @@ static int octeon_mgmt_open(struct net_device *netdev)
> >>   		/* For compensation state to lock. */
> >>   		ndelay(1040 * NS_PER_PHY_CLK);
> >>
> >> -		/* Some Ethernet switches cannot handle standard
> >> -		 * Interframe Gap, increase to 16 bytes.
> >> +		/* Default Interframe Gaps are too small.  Recommended
> >> +		 * workaround is.
> >> +		 *
> >> +		 * AGL_GMX_TX_IFG[IFG1]=14
> >> +		 * AGL_GMX_TX_IFG[IFG2]=10
> >
> > Why isn't the TX IFG just 96 bit times?
> 
> I don't have a full understanding of how the transistors are wired up on 
> the chip, so I cannot accurately answer your question.  But I can say 
> that after I empirically found the previous values to get the thing to 
> work, the hardware designers independently found that the values 
> supplied in this patch are required to achieve industry standard IFGs 
> with this hardware.

For one specific chip or for the Octeon entire family?


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