Selecting memory manager for embedded DRM device

[Alex Deucher]

On Mon, Feb 3, 2014 at 11:16 AM, Dmitry Eremin-Solenikov
<dbaryshkov at gmail.com> wrote:
> Hello,
>
> On Mon, Feb 3, 2014 at 7:49 PM, Rob Clark <robdclark at gmail.com> wrote:
>> On Sun, Feb 2, 2014 at 6:50 PM, Dmitry Eremin-Solenikov
>> <dbaryshkov at gmail.com> wrote:
>>> Hello,
>>>
>>> I'm looking onto writing DRM/KMS drivers for few pieces of
>>> embedded equipment. I stumbled upon selecting GEM/TTM/whatever
>>> for them. Could you please guide me?
>>
>> The common choices are either:
>>
>>   * TTM + GEM userspace interface (nouveau and radeon)
>>   * or just GEM (intel, and most of the ARM devices)
>>
>> TTM seems to be mostly advantageous if you need to manage migration
>> between VRAM / GART / system RAM.  But it sounds like you are talking
>> about a UMA system, so maybe TTM doesn't help you as much.
>
> Thank you for the answer. Indeed I had the feeling that just GEM would be
> work for UMA devices. I'm interested about the driver for my second hardware.
> It's a separate graphics chip with separate VRAM, no access to system
> memory and nearly no advanced capabilities (few 2D accelerations,
> but nothing fancy). Would that require TTM, some special setup of GEM
> or something completely different?

ttm can definitely handle it.  Take a look at the mgag200 or cirrus
drivers for relatively simple hardware/drivers that use ttm.

Alex