Re: [PATCH 6/6] drm/msm: add OCMEM driver

[Stanimir Varbanov <stanimir.varbanov@linaro.org>]

On 09/30/2015 02:45 PM, Rob Clark wrote:
> On Wed, Sep 30, 2015 at 7:31 AM, Rob Clark <robdclark@gmail.com> wrote:
>> On Wed, Sep 30, 2015 at 3:51 AM, Stanimir Varbanov
>> <stanimir.varbanov@linaro.org> wrote:
>>> Hi Rob,
>>>
>>> Thanks for your work.
>>>
>>> On 09/29/2015 10:48 PM, Rob Clark wrote:
>>>> For now, since the GPU is the only upstream consumer, just stuff this
>>>> into drm/msm.  Eventually if we have other consumers, we'll have to
>>>
>>> As the video encoder/decoder driver (vidc) for apq8084 && msm8974 also
>>> use the ocmem for scratch buffers, it might be better to relocate the
>>> ocmem driver in drivers/soc/qcom from the beginning?
>>
>> I wasn't really sure how soon vidc would support 8084/8974 (I assume
>> first target is 8916 which fortunately doesn't have ocmem), or if it

My expectations are that the same driver will work on apq8084, as well.

>> was mandatory or just power optimization..  but yes, the plan was to
>> move it somewhere else (not sure quite where, drivers/doc/qcom?)
>> sometime..  Preferably when someone who understands all the other
>> ocmem use-cases better could figure out what we really need to add to
>> the driver.
>>
>> In downstream driver there is a lot of complexity that appears to be
>> in order to allow two clients to each allocate a portion of a macro
>> within a region (ie. aggregate_macro_state(), apply_macro_vote(),
>> etc), and I wanted to figure out if that is even a valid use-case
>> before trying to make ocmem something that could actually support
>> multiple clients.
>>
>> There is also some complexity about ensuring that if clients aren't
>> split up on region boundaries, that you don't have one client in
>> region asking for wide-mode and other for narrow-mode..
>> (switch_region_mode()) but maybe we could handle that by just
>> allocating wide from bottom and narrow from top.  Also seems to be
>> some craziness for allowing one client to pre-empt/evict another.. a
>> dm engine, etc, etc..
>>
>> All I know is gpu just statically allocates one big region aligned
>> chunk of ocmem, so I ignored the rest of the crazy (maybe or maybe not
>> hypothetical) use-cases for now...

OK, I will try to sort out ocmem use cases for vidc driver.

> 
> btw, I should add that I don't mind adding it in drivers/soc/qcom (or
> somewhere else?) to start with if others prefer, I just didn't want to
> give the wrong impression that it is ready yet for multiple clients.

I see. Then to avoid confusions you could remove all clients and keep
only graphics from ocmem_client enum.

> 
> All I know is the gpu uses it statically and is pretty much useless
> without ocmem, so for lack of understanding of the other use cases I
> just tried to add simply what the gpu needs..

Got it now, thanks.

-- 
regards,
Stan