Re: [PATCH net-next V2 06/16] net: fec: don't clear all rx queue bits when just one is being checked

[Troy Kisky <troy.kisky@boundarydevices.com>]

On 3/4/2016 9:38 AM, Russell King - ARM Linux wrote:
> On Fri, Mar 04, 2016 at 09:18:19AM -0700, Troy Kisky wrote:
>> On 3/4/2016 2:11 AM, Fugang Duan wrote:
>>> From: Troy Kisky <troy.kisky@boundarydevices.com>Sent: Thursday, February 25, 2016 8:37 AM
>>>> To: netdev@vger.kernel.org; davem@davemloft.net; b38611@freescale.com
>>>> Cc: fabio.estevam@freescale.com; l.stach@pengutronix.de; andrew@lunn.ch;
>>>> tremyfr@gmail.com; linux@arm.linux.org.uk; linux-arm-
>>>> kernel@lists.infradead.org; laci@boundarydevices.com; shawnguo@kernel.org;
>>>> johannes@sipsolutions.net; stillcompiling@gmail.com;
>>>> sergei.shtylyov@cogentembedded.com; arnd@arndb.de; Troy Kisky
>>>> <troy.kisky@boundarydevices.com>
>>>> Subject: [PATCH net-next V2 06/16] net: fec: don't clear all rx queue bits when
>>>> just one is being checked
>>>>
>>>> FEC_ENET_RXF is 3 separate bits, we only check one queue at a time. So, when
>>>> the last queue is being checked, it is bad to remove the interrupt on the 1st
>>>> queue.
>>>>
>>>> Also, since this is now done in the napi routine and not the interrupt, it is not
>>>> needed.
>>>>
>>>> Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
>>>> ---
>>>>  drivers/net/ethernet/freescale/fec_main.c | 2 --
>>>>  1 file changed, 2 deletions(-)
>>>>
>>>> diff --git a/drivers/net/ethernet/freescale/fec_main.c
>>>> b/drivers/net/ethernet/freescale/fec_main.c
>>>> index 610cf6c..791f385 100644
>>>> --- a/drivers/net/ethernet/freescale/fec_main.c
>>>> +++ b/drivers/net/ethernet/freescale/fec_main.c
>>>> @@ -1338,8 +1338,6 @@ static int fec_rxq(struct net_device *ndev, struct
>>>> fec_enet_private *fep,
>>>>  			break;
>>>>  		pkt_received++;
>>>>
>>>> -		writel(FEC_ENET_RXF, fep->hwp + FEC_IEVENT);
>>>> -
>>>
>>> We should clear the related rx queue ievent, not remove the code.
>>> Pls see commit: db3421c114cf that was submitted by Russell King.
>>>
>>> No ack the patch.
>>
>>
>> This is now done in patch #4 "net: fec: reduce interrupts" and you could argue
>> that it should be squashed into that patch. But I like separating changes
>> as much as possible.
>>
>>
>> Russell, this patch and patch #4 will likely need your ack before it will be applied.
>> Can you take a look please?
> 
> I stopped caring about the FEC ethernet driver about 18 months ago,
> after I ended up dropping a significant pile of fixes on the floor
> through the huge number of conflicts and the shere effort of
> constantly trying to move them forward.
> 
> My patch series tend to be large because I put concentrated effort
> into something for a month, which then gives a problem if conflicts
> come up later and the series has to be effectively rewritten from
> scratch.  It was after the second or third time of facing an almost
> total rewrite that happened that I just gave up.
> 
> I've toyed with the idea of forking the driver, but I wouldn't have
> time to maintain such a thing.  So, right now I just put up with all
> the bad quirks, and reset/power cycle the boards when things go wrong.
> Right now, I just disable runtime PM support on the FEC to get
> stability here. :)
> 
> Sorry, but I can't be of more help.
> 


I can sympathize, I've been almost ready to post my patches numerous times
when a huge patch set would hit, and conflict everywhere. Including once
about 18 months ago :)

That's why I got trigger happy, and first posted my too large set before
net-next was opened. It didn't help though, there was already a conflict
in net.


Troy