netdev - Re: [PATCH] e100 rx: or s and el bits

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Date:	Tue, 01 May 2007 08:21:33 -0700
From:	"Kok, Auke" <auke-jan.h.kok@...el.com>
To:	Milton Miller <miltonm@....com>
CC:	Scott Feldman <sfeldma@...ox.com>, Jeff Garzik <jeff@...zik.org>,
	e1000-devel@...ts.sourceforge.net, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	John Ronciak <john.ronciak@...el.com>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
Subject: Re: [PATCH] e100 rx: or s and el bits

Milton Miller wrote:
> In commit d52df4a35af569071fda3f4eb08e47cc7023f094, the description
> talks about emulating another driver by setting addtional bits and
> the being unable to test when submitted.  Seeing the & operator to
> set more bits made me suspicious, and indeed the bits are defined
> in positive logic:
> 
> 	cb_s      = 0x4000,
> 	cb_el     = 0x8000,
> 
> So anding those together would be 0.   I'm guessing they should
> be or'd, but don't have hardware here to test, much like the
> committed patch.  In fact, I'll let someone else do the compile
> test too.  I'll update the comment.
> 
> (It looks like the end of list and s bits would not be set
> in the template nor cleared when linking in recieve skbs, so
> as long as the kernel can keep up with the 100Mb card we 
> wouldn't see the adapter go off the linked list, possibly
> explaining any successful use of this patch written against
> 2.6.14).

yes, that definately doesn't seem right. I'll try to run this and watch out for 
David Ackers report as well.

Thanks,

Auke


> 
> Signed-off-by: Milton Miller <miltonm@....com>
> 
> 
> --- linux-2.6/drivers/net/e100.c.orig	2007-05-01 05:19:17.000000000 -0500
> +++ linux-2.6/drivers/net/e100.c	2007-05-01 05:22:14.000000000 -0500
> @@ -947,7 +947,7 @@ static void e100_get_defaults(struct nic
>  		((nic->mac >= mac_82558_D101_A4) ? cb_cid : cb_i));
>  
>  	/* Template for a freshly allocated RFD */
> -	nic->blank_rfd.command = cpu_to_le16(cb_el & cb_s);
> +	nic->blank_rfd.command = cpu_to_le16(cb_el | cb_s);
>  	nic->blank_rfd.rbd = 0xFFFFFFFF;
>  	nic->blank_rfd.size = cpu_to_le16(VLAN_ETH_FRAME_LEN);
>  
> @@ -1769,13 +1769,13 @@ static int e100_rx_alloc_skb(struct nic 
>  	}
>  
>  	/* Link the RFD to end of RFA by linking previous RFD to
> -	 * this one, and clearing EL bit of previous.  */
> +	 * this one, and clearing EL and S bit of previous.  */
>  	if(rx->prev->skb) {
>  		struct rfd *prev_rfd = (struct rfd *)rx->prev->skb->data;
>  		put_unaligned(cpu_to_le32(rx->dma_addr),
>  			(u32 *)&prev_rfd->link);
>  		wmb();
> -		prev_rfd->command &= ~cpu_to_le16(cb_el & cb_s);
> +		prev_rfd->command &= ~cpu_to_le16(cb_el | cb_s);
>  		pci_dma_sync_single_for_device(nic->pdev, rx->prev->dma_addr,
>  			sizeof(struct rfd), PCI_DMA_TODEVICE);
>  	}
-
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