RE: [lwip-users] Misalignment problems on PowerPC (little endian mode)

[Bill Auerbach]

Hi Ikhwan,

 

I’m currently using Freescale CodeWarrior  Power Architecture C/C++ compiler – Ver 8.8.1 (latest version) for the MPC8349EA PPC processor.

 

In Big-endian mode of course.  lwIP performance and bandwidth are excellent and extended saturated TCP bandwidth receive tests (over 3 billion packets continuous) has been perfect.  It took some time to work around a memory coherency or lockup problem in the PowerPC that I’m still working with Freescale on trying to figure out if it’s me doing something I shouldn’t be doing or not.  There’s an extensive errata on this part including 2 problems with TSEC lockups – neither of which appear to be what I’m seeing.

 

Bill

 

From: address@hidden [mailto:address@hidden On Behalf Of Muhamad Ikhwan Ismail
Sent: Saturday, May 10, 2008 1:09 AM
To: Mailing list for lwIP users
Subject: RE: [lwip-users] Misalignment problems on PowerPC (little endian mode)

 

 
Hi Bill
 
Well I wish I could do it in big endian for the PowerPC, since the PowerPC corrects the alignment
problems in the hardware itself in big endian mode. Unfortunately the project itself requires me
to do it little endian. Which compiler did you use last time ?
 
Greetings
Ikhwan

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> Date: Fri, 9 May 2008 17:30:10 +0200
> From: address@hidden
> To: address@hidden
> Subject: Re: [lwip-users] Misalignment problems on PowerPC (little endian mode)
>
> Muhamad Ikhwan Ismail wrote:
> >
> > Hi,
> >
> > Thanks Bill and Simon. Simon is right, my payload is aligned. The
> > problem arises when the Ethernet header
> > gets stripped, the IP addr field is not aligned when it gets accessed.
> > And I didnt know structure packing is a must. Then I have to
> > find a way to make my port works. Meaning even if i fixed my ip addr
> > processing macros and functions, Ill still get problems ?
> I'm not sure but I think so, yeah. The reason is the same reason
> 'network byte order' is used: when you exchange data over the network,
> everyone would have to use the same alignment. Instead, packing is used.
> > I thought i woulnt since all e.g TCP header fields are 2 bytes aligned ?
> At least DNS had a problem with non-packed mode, I think. DHCP could
> have problems, too...
>
> Simon
>
>
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> lwip-users mailing list
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> http://lists.nongnu.org/mailman/listinfo/lwip-users

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