[radeon]Question about create ring BO in VRAM

[Chen Jie]

2011/11/5 Alex Deucher <alexdeucher at gmail.com>:
> On Fri, Nov 4, 2011 at 10:26 AM, Chen Jie <chenj at lemote.com> wrote:
>> Hi all,
>>
>> I tried to create/pin ring BO in VRAM instead of GTT to debug some
>> ring-related problems. After I did this, it rendered a black screen in
>> X (on a X86 RS780E board), but radeon.test passed.
>> 'ps aux' shows X uninterruptibly sleeps on radeon.
>>
>> Curious why this does not work?
>
> The tricky part is dealing with the HDP cache.  Access to vram via the
> PCI FB BAR goes through the HDP cache, you have to make sure it's
> flushed properly before the GPU starts using the data there.  To flush
> it, either read back from vram, or write 1 to the
> HDP_MEM_COHERENCY_FLUSH_CNTL register.  We generally don't recommend
> putting the ring in vram.
Get it, thanks.
After add HDP cache flush in r600_cp_commit(), it works fine.



Regards,
-- Chen Jie