Subject: Re: [PATCH] arch/ppc/8xx_io/enet.c, version 2

From: "Hans Feldt" <[email-masked]>
Date: Wed, 13 Nov 2002 20:30:41 +0100

----- Original Message -----
From: Joakim Tjernlund <[email-masked]>

> You may be right, perhaps one must invalidate the whole buffer before giving it
> to the CPM/DMA. Suppose you reuse a buffer which has been modified before it
> was freed and the dcache must write back data to free up space and the buffer,
> which now is owned by the CPM, get written to.

I beleive this could happen. Since IP does not perform checksumming
but relies on the link (don't know this really) in that matter, I guess
the application could get wrong data...

> I have not seen any corrupted packets and you are the first to report
> any problems.

Did you run any data integrity tests?

> What modifications have you done?

I haven't used your driver patch. I used the __idea__ of delaying the
invalidate to the point where you know how much has been received. This was
in an RTOS ATM driver for a 405. An integrity test showed that some few
packets was wrong. Data was changed by means of cache lines.

> What CPU?
> Post the driver please.

Irrelevant, non-linux

Cheers,
Hans

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