Re: [PATCH v4] drm/ttm: Clarify that the TTM_PL_SYSTEM is under TTMs control

[Zack Rusin <zackr@vmware.com>]

On Wed, 2021-11-10 at 09:50 -0500, Zack Rusin wrote:
> TTM takes full control over TTM_PL_SYSTEM placed buffers. This makes
> driver internal usage of TTM_PL_SYSTEM prone to errors because it
> requires the drivers to manually handle all interactions between TTM
> which can swap out those buffers whenever it thinks it's the right
> thing to do and driver.
> 
> CPU buffers which need to be fenced and shared with accelerators
> should
> be placed in driver specific placements that can explicitly handle
> CPU/accelerator buffer fencing.
> Currently, apart, from things silently failing nothing is enforcing
> that requirement which means that it's easy for drivers and new
> developers to get this wrong. To avoid the confusion we can document
> this requirement and clarify the solution.
> 
> This came up during a discussion on dri-devel:
> https://lore.kernel.org/dri-devel/232f45e9-8748-1243-09bf-56763e6668b3@amd.com


Polite and gentle ping on that one. Are we ok with the wording here?

z