[PATCH v2 0/3] ast, mgag200: Map console BO while it's being displayed

Thomas Zimmermann tzimmermann at suse.de
Fri Sep 6 08:10:28 UTC 2019


Hi

Am 05.09.19 um 11:29 schrieb Gerd Hoffmann:
> On Thu, Sep 05, 2019 at 10:19:40AM +0200, Thomas Zimmermann wrote:
>> Hi
>>
>> Am 05.09.19 um 09:56 schrieb Daniel Vetter:
>>> On Thu, Sep 5, 2019 at 9:01 AM Gerd Hoffmann <kraxel at redhat.com> wrote:
>>>>
>>>>   Hi,
>>>>
>>>>> - imo we should fix this by using the io_mapping stuff, that avoids
>>>>> the overhead of repeated pat checks for map/unmap.
>>>>
>>>> Another idea:  IIRC ttm has a move_notify callback.  So we could simply
>>>> keep mappings active even when the refcount goes down to zero.  Then do
>>>> the actual unmap either in the move_notify or in the destroy callback.
>>>
>>> Yeah that should be a really clean solution, and only needs changes in
>>> the vram helpers. Which is nice, more common code!
>>
>> But the console's BO is special wrt to mapping. Putting special code for
>>  console handling into vram helpers doesn't seem right.
> 
> I have no special handling in mind.  I think we can simply do that for
> all gem objects, no matter whenever they are created by fbcon or
> userspace (wayland/xorg/whatever).  vmap will create a mapping (or
> increase the reference count).  vunmap decreases the reference count,
> when it goes down to zero unpin it but keep the mapping.  The actual
> unmap happens when ttm wants move the object from VRAM to SYSTEM due to
> VRAM being full.  In case vram has room for all our objects we simply
> never unmap.

That's pretty cool. Thanks for clarifying. I think it's the solution I
was looking for.

Best regards
Thomas

> 
> hope this clarifies,
>   Gerd
> 
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-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany
GF: Felix Imend├Ârffer, Mary Higgins, Sri Rasiah
HRB 21284 (AG N├╝rnberg)

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