netdev - Re: [PATCH net-next 2/2] tg3: Scale back code that modifies MRRS

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Date:	Mon, 28 Nov 2011 14:45:58 -0800
From:	"Matt Carlson" <mcarlson@...adcom.com>
To:	"Ben Hutchings" <bhutchings@...arflare.com>
cc:	"Matthew Carlson" <mcarlson@...adcom.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Michael Chan" <mchan@...adcom.com>
Subject: Re: [PATCH net-next 2/2] tg3: Scale back code that modifies
 MRRS

On Mon, Nov 28, 2011 at 11:53:56AM -0800, Ben Hutchings wrote:
> On Mon, 2011-11-28 at 11:41 -0800, Matt Carlson wrote:
> > Tg3 normally gets a performance boost by increasing the PCI Maximum Read
> > Request Size (MRRS) to 4k.  Unfortunately, this is causing some problems
> > on particular hardware platforms.  This patch removes all code that
> > modifies the MRRS except for one case.
> > 
> > As part of a solution to fix an internal FIFO problem on the 5719, the
> > driver artificially capped the MRRS to 2k for the entire 5719, and later
> > 5720, ASIC revs.  This was overly aggressive and only really needed to
> > be done for the 5719 A0.  In the spirit of the rest of this patch, the
> > driver will only reprogram the MRRS for this device if the value exceeds
> > the 2k cap.
> [...]
> 
> It may be better to do this as a PCI quirk, so that the generic MPS/MRRS
> configuration code has this information.

If at all possible, I'd rather do that as a follow-on patch.  This patch
fixes a critical problem that is blocking a lot of testing.

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