netdev - Re: [PATCH] fix e100 rx path on ARM (was [PATCH] e100 rx: or s and el bits)

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Message-ID: <4672A4A0.4070806@garzik.org>
Date:	Fri, 15 Jun 2007 10:39:28 -0400
From:	Jeff Garzik <jeff@...zik.org>
To:	Milton Miller <miltonm@....com>
CC:	Jeff Garzik <jgarzik@...ox.com>, e1000-devel@...ts.sourceforge.net,
	David Acker <dacker@...net.com>, netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	"Kok, Auke" <auke-jan.h.kok@...el.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Scott Feldman <sfeldma@...ox.com>,
	John Ronciak <john.ronciak@...el.com>
Subject: Re: [PATCH] fix e100 rx path on ARM (was [PATCH] e100 rx: or s and
 el bits)

Milton Miller wrote:
> 
> On Jun 6, 2007, at 4:28 AM, Milton Miller wrote:
> 
>>
>> On Jun 5, 2007, at 9:26 PM, Kok, Auke wrote:
>>
>>> Kok, Auke wrote:
>>>>>
>>>> Hmm git-revert seems to do the job right. I checked it with git-show 
>>>> | patch -p1 -R and the results look OK. The two patches on top of 
>>>> the one we want to revert are unrelated enough to apply (manually it 
>>>> shows some fuzz, but otherwise it's OK).
>>>> Jeff, please `git-revert d52df4a35af569071fda3f4eb08e47cc7023f094` 
>>>> to revert the following patch for now:
>>>> ---
>>>> commit  d52df4a35af569071fda3f4eb08e47cc7023f094
>>>> Author: Scott Feldman <sfeldma@...ox.com>
>>>> Date:   Wed Nov 9 02:18:52 2005 -0500
>>>>      [netdrvr e100] experiment with doing RX in a similar manner to 
>>>> eepro100
>>>>      I was going to say that eepro100's speedo_rx_link() does the 
>>>> same DMA
>>>>      abuse as e100, but then I noticed one little detail: eepro100 
>>>> sets  both
>>>>      EL (end of list) and S (suspend) bits in the RFD as it chains 
>>>> it  to the
>>>>      RFD list.  e100 was only setting the EL bit.  Hmmm, that's  
>>>> interesting.
>>>>      That means that if HW reads a RFD with the S-bit set,  it'll 
>>>> process
>>>>      that RFD and then suspend the receive unit.  The  receive unit 
>>>> will
>>>>      resume when SW clears the S-bit.  There is no need  for SW to 
>>>> restart
>>>>      the receive unit.  Which means a lot of the receive  unit state 
>>>> tracking
>>>>      code in the driver goes away.
>>>>      So here's a patch against 2.6.14.  (Sorry for inlining it; the 
>>>> mailer
>>>>      I'm using now will mess with the word wrap).  I can't test this on
>>>>      XScale (unless someone has an e100 module for Gumstix :) .  It 
>>>> should
>>>>      be doing exactly what eepro100 does with RFDs.  I don't believe 
>>>> this
>>>>      change will introduce a performance hit because the S-bit and 
>>>> EL-bit  go
>>>>      hand-in-hand meaning if we're going to suspend because of the 
>>>> S- bit,
>>>>      we're on the last resource anyway, so we'll have to wait for SW 
>>>>  to
>>>>      replenish.
>>>>      (cherry picked from 29e79da9495261119e3b2e4e7c72507348e75976 
>>>> commit)
>>>> ---
>>>
>>> A little bit more is needed to explain why we're reverting it for 
>>> now. Jeff, please insert this into the revert commit.
>>>
>>> Auke
>>>
>>> -- 
>>> This patch attempted to fix e100 for non-cache coherent memory 
>>> architectures by using the cb style code that eepro100 had and using 
>>> the EL and s bits from the RFD list. Unfortunately the hardware 
>>> doesn't work exactly like this and therefore this patch actually 
>>> breaks e100 on those systems.
>>
>> on all systems.  (Both the &| typo and the removed restart logic).
>>
>>> Reverting the change brings it back to the previously known good 
>>> state for 2.6.22. The pending rewrite in progress to this code can 
>>> then be safely merged later.
>>>
>>> Signed-off-by: Auke Kok <auke-jan.h.kok@...el.com>
>>>
> 
> Jeff I don't see this in netdev upstream-fixes.  Are you waiting on Auke 
> to respond to this?

It should now be upstream, as of a day or two ago.

Sorry for the delaying, was travelling, and wound up accidentally losing 
Auke's commit description.

	Jeff



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