Re: Bug: Latest (rc2 and beyond) kernel fails on Dreamcast

[Adrian McMenamin <lkmladrian@gmail.com>]

2009/1/20 Paul Mundt <lethal@linux-sh.org>:
> On Mon, Jan 19, 2009 at 10:33:57PM +0000, Adrian McMenamin wrote:
>> 2009/1/19 Adrian McMenamin <lkmladrian@gmail.com>:
>> > I haven't had time to look at this, but the most up to date kernel
>> > (and the one of around a week ago also) fails to boot, seemingly
>> > seeking an IP address for the 8139too based NIC.
>>
>> > [    4.664236] Sending DHCP requests .<3>eth0: PCI Bus error 2200.
>> > [    4.669582] eth0: PCI Bus error 2200.
>>
>> And the bisection reveals the following:
>>
>> adrian@bossclass:~/linux-2.6$ git bisect bad
>> 58c6d3dfe436eb8cfb451981d8fdc9044eaf42da is first bad commit
>> commit 58c6d3dfe436eb8cfb451981d8fdc9044eaf42da
>> Author: Johannes Weiner <hannes@cmpxchg.org>
>> Date:   Tue Jan 6 14:43:10 2009 -0800
>>
>>     dma-coherent: catch oversized requests to dma_alloc_from_coherent()
>>



>
> The dreamcast uses a 32kB coherent area for PCI DMA, which all of the
> 8139too allocations should fit under just fine. What does
> dma_alloc_from_coherent() say the requested size is, vs the per-device
> memory size for each allocation?
>

Hmmm...

From printks I stuck in the code

[    3.641267] Size is 0x1800, mem->size is 0x8
[    3.644996] Size is 0x2810, mem->size is 0x8

The sizes are correct - the first is the TX buffer, the second RX, but
I have no idea why mem->size is set so low, I assume that is a bug
somewhere else in the Dreamcast code. Any clues gratefully received.