Linux 2.6.39-rc3

Alex Deucher alexdeucher at
Mon Apr 18 09:35:15 PDT 2011

On Mon, Apr 18, 2011 at 11:59 AM, Jerome Glisse <j.glisse at> wrote:
> On Mon, Apr 18, 2011 at 11:33 AM, Alex Deucher <alexdeucher at> wrote:
>> On Mon, Apr 18, 2011 at 11:29 AM, Jerome Glisse <j.glisse at> wrote:
>>> On Mon, Apr 18, 2011 at 11:23 AM, Alex Deucher <alexdeucher at> wrote:
>>>> On Sun, Apr 17, 2011 at 10:09 AM, Joerg Roedel <joro at> wrote:
>>>>> On Sat, Apr 16, 2011 at 02:54:04PM -0400, Jerome Glisse wrote:
>>>>>> If you want to go the printk way you can add printk before each test
>>>>>> ring_test, ib_test in r600.c this 2 functions are the own that might
>>>>>> trigger the first GPU gart activities.
>>>>> Okay, I found the place in source that triggers this. It happens in the
>>>>> function r600_ib_test. The interesting thing is that not the ib-command
>>>>> itself is responsible but the fence that is emitted afterwards (proved
>>>>> by removing the fence command, where the problem went away).
>>>>> I don't know enough about the command semantics to make a guess what
>>>>> goes wrong there. But maybe you GPU folks have an idea?
>>>> I can't think of anything off hand.  It might be worth disabling the
>>>> call to r600_ib_test() in r600_init() and then seeing if you get any
>>>> errors when the fences are used later on when X starts or just at that
>>>> point in the module load sequence.  What's odd is that when you tested
>>>> radeon.no_wb=1 you got the same behavior as that disables shadowing of
>>>> fence writes to gpu gart mem, so it wouldn't be writing to memory in
>>>> that case.
>>>> Alex
>>> It might be the irq ring write that is faulty.
>> That's disabled with no_wb=1 as well.
>> Alex
> I mean the irq interrupt ring, i don't see this being disabled when no_wb=1

I meant the IH ring pointer writeback.  The ih ring itself is still in
gart memory.


> Cheers,
> Jerome

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