netdev - RE: [PATCH net-next 5/7] net:fec: add support for dumping transmit ring on timeout

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Message-ID: <063D6719AE5E284EB5DD2968C1650D6D0F70156E@AcuExch.aculab.com>
Date:	Tue, 29 Apr 2014 14:23:09 +0000
From:	David Laight <David.Laight@...LAB.COM>
To:	'Frank Li' <lznuaa@...il.com>
CC:	Frank Li <Frank.Li@...escale.com>,
	"shawn.guo@...aro.org" <shawn.guo@...aro.org>,
	"B38611@...escale.com" <B38611@...escale.com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"rmk+kernel@....linux.org.uk" <rmk+kernel@....linux.org.uk>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: [PATCH net-next 5/7] net:fec: add support for dumping transmit
 ring on timeout

From: Frank Li [mailto:lznuaa@...il.com]
> On Tue, Apr 29, 2014 at 9:01 AM, David Laight <David.Laight@...lab.com> wrote:
> > From: Frank ...
> >> > You probably want the read and write indexes as well.
> >>
> >>                      bdp == fep->cur_tx ? 'S' : ' ',
> >>                      bdp == fep->dirty_tx ? 'H' : ' ',
> >>
> >> Above code already print read and write index. 'S', 'H'
> >
> > Gah I must be asleep!
> > Something made be think that was to do with the ring ownership bit!
> 
> I think it is same thing. If I am wrong, please tell me difference.

The ownership bit in the ring flags - that the hardware uses.
Which are printed in the next field.

I'm guessing that the reason the tx ring is 'interesting' is that there
have been bugs where the driver and hardware disagree about which entry
each should process next.
Otherwise the full tx ring is likely to be very very boring.

	David