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

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Date:	Wed, 19 Jun 2013 18:08:07 -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 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'm also confused a bit here by the difference between the
bsd implementation and yours.

http://fxr.watson.org/fxr/source/contrib/octeon-sdk/cvmx-csr-typedefs.h?v=FREEBSD8

 2628  * * Programming IFG1 and IFG2.
 2629  * 
 2630  *   For half-duplex systems that require IEEE 802.3 compatibility, IFG1 must
 2631  *   be in the range of 1-8, IFG2 must be in the range of 4-12, and the
 2632  *   IFG1+IFG2 sum must be 12.
 2633  * 
 2634  *   For full-duplex systems that require IEEE 802.3 compatibility, IFG1 must
 2635  *   be in the range of 1-11, IFG2 must be in the range of 1-11, and the
 2636  *   IFG1+IFG2 sum must be 12.
 2637  * 
 2638  *   For all other systems, IFG1 and IFG2 can be any value in the range of
 2639  *   1-15.  Allowing for a total possible IFG sum of 2-30.
 2640  * 
 2641  * Additionally reset when both MIX0/1_CTL[RESET] are set to 1.

>  		 */
> -		cvmx_write_csr(CVMX_AGL_GMX_TX_IFG, 0x88);
> +		cvmx_write_csr(CVMX_AGL_GMX_TX_IFG, 0xae);
>  	}
>  
>  	octeon_mgmt_rx_fill_ring(netdev);

I don't have a datasheet.  Is one available?

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