linux-kernel - Re: Strange transmit corruption in jsm driver on geode sc1200 system

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Date:	Fri, 25 Aug 2006 22:20:17 +0100
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Lennart Sorensen <lsorense@...lub.uwaterloo.ca>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Strange transmit corruption in jsm driver on geode sc1200
	system

Ar Gwe, 2006-08-25 am 16:30 -0400, ysgrifennodd Lennart Sorensen:
> The driver is doing memcpy_toio to tranfer data to the transmit FIFO
> (which is a 64byte memory mapped block of memory on the PCI bus as far
> as I can tell).  The data in the transmit queue is in the right order

That should be staying in order unless the device memory is mislabelled
and prefetchable etc.

> being passed to memcpy_toio, but somehow by the time it is in the uart
> and goes out the transmiter, every 4th byte is moved 3 bytes back.

What happens if you swap the memcpy_toio with while() writeb() ?

> I read something about the geodes doing memory write reordering, but
> that it is supposed to magically not screw up PCI writes.  I have no
> idea if it is or not though.

They do a lot of stuff but it should not affect the PCI side and I'd
expect it to do other things than byte lane re-ordering.

> Does anyone have any suggestions for something to try?

Is the buffer 32bit aligned ?


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