netdev - Re: MSI-X vector count on 82754L

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Date:	Mon, 19 Sep 2011 16:56:09 -0700
From:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>
To:	Arnaud Lacombe <lacombar@...il.com>
Cc:	"Allan, Bruce W" <bruce.w.allan@...el.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Vogel, Jack" <jack.vogel@...el.com>
Subject: Re: MSI-X vector count on 82754L

On Sun, 2011-09-18 at 22:34 -0700, Arnaud Lacombe wrote:
> [fixing address of the netdev@ list, sorry - A.]
> 
> On Mon, Sep 19, 2011 at 1:31 AM, Arnaud Lacombe <lacombar@...il.com> wrote:
> > Hi folks,
> >
> > In:
> >
> > commit 4662e82b2cb41c60826e50474dd86dd5c6372b0c
> > Author: Bruce Allan <bruce.w.allan@...el.com>
> > Date:   Tue Aug 26 18:37:06 2008 -0700
> >
> >    e1000e: add support for new 82574L part
> >
> >    This new part has the same feature set as previous parts with the addition
> >    of MSI-X support.
> >
> >    Signed-off-by: Bruce Allan <bruce.w.allan@...el.com>
> >    Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> >    Signed-off-by: Jeff Garzik <jgarzik@...hat.com>
> >
> > MSI-X support was added to the e1000e driver, later on slightly reworked by:
> >
> > commit 8e86acd7d5968e08b3e1604e685a8c45f6fd7f40
> > Author: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> > Date:   Mon Aug 2 14:27:23 2010 +0000
> >
> >    e1000e: Fix irq_synchronize in MSI-X case
> >
> >    Based on original patch/work from Jean Delvare <jdelvare@...e.de>
> >    Synchronize all IRQs when in MSI-X IRQ mode.
> >
> >    Jean's original patch hard coded the sync with the 3 possible vectors,
> >    this patch incorporates more flexibility for the future and aligns
> >    with how igb stores the number of vectors into the adapter structure.
> >
> >    CC: Jean Delvare <jdelvare@...e.de>
> >    Cc: Jesse Brandeburg <jesse.brandeburg@...el.com>
> >    Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@...el.com>
> >    Tested-by: Jeff Pieper <jeffrey.e.pieper@...el.com>
> >    Acked-by: Bruce Allan <bruce.w.allan@...el.com>
> >    Signed-off-by: David S. Miller <davem@...emloft.net>
> >
> > [It is unclear to what "Jean" does this commit log refers to, as the
> > support MSI-X was added Bruce, anyway...]
> >
> > Why only 3 vectors are used when both the product brief and the
> > datasheet advertise up to 5 MSI-X vector usable by the chip ? That is
> > 2*RX + 2*TX.
> >
> > Thanks in advance,
> >  - Arnaud
> >

The e1000e driver is only a single queue driver so it does not need more
than 3 vectors, that is the reason we only use the 3 vectors.

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