[PATCH] spidernet: don't use debug flag

[PATCH] spidernet: don't use debug flag

[Ishizaki Kou]

GDTDCEIDIS flag is defined that it is for debug and should not be used.
We met some troubles on Celleb platform by setting this flag.
 -network does not recover after ifconfig down, then up operations.

Signed-off-by: Kou Ishizaki <kou.ishizaki@toshiba.co.jp>
---

Index: linux-powerpc-git/drivers/net/spider_net.h
diff -u linux-powerpc-git/drivers/net/spider_net.h:1.1.1.4 linux-powerpc-git/drivers/net/spider_net.h:1.8
--- linux-powerpc-git/drivers/net/spider_net.h:1.1.1.4	Tue Jul  3 15:43:24 2007
+++ linux-powerpc-git/drivers/net/spider_net.h	Fri Jul  6 14:07:00 2007
@@ -222,7 +222,6 @@
 #define SPIDER_NET_GDTBSTA             0x00000300
 #define SPIDER_NET_GDTDCEIDIS          0x00000002
 #define SPIDER_NET_DMA_TX_VALUE        SPIDER_NET_TX_DMA_EN | \
-                                       SPIDER_NET_GDTDCEIDIS | \
                                        SPIDER_NET_GDTBSTA
 
 #define SPIDER_NET_DMA_TX_FEND_VALUE	0x00030003

Re: [PATCH] spidernet: don't use debug flag

[Linas Vepstas]

On Mon, Jul 09, 2007 at 05:45:21PM +0900, Ishizaki Kou wrote:
> GDTDCEIDIS flag is defined that it is for debug and should not be used.

!? Certainly, my spec doesn't say anything like this;
I don't know of any other way of turning off the descriptor 
chain end interrupt; leaving it on hurts performance in a big way.

I get the following TX performance numbers:

pkt sz       rate w/o patch      rate w/patch
(bytes)      (Mbits/sec)         (Mbits/sec)
-------      ----------          ---------
400            503                 353
200            239                  88
100            122                  44
 60             73                  26

That's not quite a 3x performance degradation.

In addition, with your patch, the number of interrupts jumps
from just about zero, to about 55K/second. From what I can tell, 
this huge interrupt rate eats up all the CPU cycles, which is
why the performance drops so drasically.

> We met some troubles on Celleb platform by setting this flag.
>  -network does not recover after ifconfig down, then up operations.

Can you be more specific?  I can't imagine why this flag would
have anything to do with ifdown/ifup. The device open/close 
routines should reset all hardware state; this shouldn't make
any difference. (It doesn't for me, at least).  

--linas

Re: [Cbe-oss-dev] [PATCH] spidernet: don't use debug flag

[Ishizaki Kou]

Linas-san,

> > GDTDCEIDIS flag is defined that it is for debug and should not be
used.
> 
> !? Certainly, my spec doesn't say anything like this;

First, I'm sorry to say that GDTDCEDIS is for debug. It's my
misunderstanding.

My HW manual of SCC simply said that GDTDCEDIS must not be set(Is 
it same for you?).  But I don't know concretely what will go wrong 
by setting this bit.

> I don't know of any other way of turning off the descriptor 
> chain end interrupt; leaving it on hurts performance in a big way.
> 
> I get the following TX performance numbers:
> 
> pkt sz       rate w/o patch      rate w/patch
> (bytes)      (Mbits/sec)         (Mbits/sec)
> -------      ----------          ---------
> 400            503                 353
> 200            239                  88
> 100            122                  44
>  60             73                  26
> 
> That's not quite a 3x performance degradation.
> 
> In addition, with your patch, the number of interrupts jumps
> from just about zero, to about 55K/second. From what I can tell, 
> this huge interrupt rate eats up all the CPU cycles, which is
> why the performance drops so drasically.

I understand the influence for performance by setting GDTDCEDIS and
why you set this bit.

> > We met some troubles on Celleb platform by setting this flag.
> >  -network does not recover after ifconfig down, then up operations.
> 
> Can you be more specific?  I can't imagine why this flag would
> have anything to do with ifdown/ifup. The device open/close 
> routines should reset all hardware state; this shouldn't make
> any difference. (It doesn't for me, at least).  

Sorry, I have no more information that ifconfig down/up commands. All
about I know is that I met the phenomenon when GDTDCEDIS is set.

I need more investigation. Please drop the patch.

Best regards,
Kou Ishizaki

Re: [Cbe-oss-dev] [PATCH] spidernet: don't use debug flag

[Linas Vepstas]

On Wed, Jul 11, 2007 at 04:57:38PM +0900, Ishizaki Kou wrote:
[...]
> I need more investigation. Please drop the patch.

OK.

--linas

p.s. I tested ifdown/ifup, and didn't see any problems.
Does your bug happen immediately, or does it take many attempts 
to trigger it?

Re: [Cbe-oss-dev] [PATCH] spidernet: don't use debug flag

[Ishizaki Kou]

Linas-san,

> p.s. I tested ifdown/ifup, and didn't see any problems.
> Does your bug happen immediately, or does it take many attempts 
> to trigger it?

Thanks for your testing.

It happens immediately in our environment. It may be celleb specific.

Best regards,
Kou Ishizaki