[alsa-devel] [PATCH 2/3] ASoC: Davinci: pcm: add support for sram-support-less platforms

[Porter, Matt]

On Oct 4, 2012, at 5:21 AM, Daniel Mack wrote:

> 
> 
> On 02.10.2012 18:50, Daniel Mack wrote:
>> On 02.10.2012 18:41, Matt Porter wrote:
>>> On Tue, Oct 02, 2012 at 03:42:47PM +0200, Daniel Mack wrote:
>>>> On 02.10.2012 13:06, Sekhar Nori wrote:
>>>>> On 10/2/2012 4:03 PM, Daniel Mack wrote:
>>>>>> On 02.10.2012 11:37, Mark Brown wrote:
>>>>>>> On Tue, Oct 02, 2012 at 10:48:53AM +0300, Peter Ujfalusi wrote:
>>>>>>> 
>>>>>>>> I also agree that ifdef is not a good solution.
>>>>>>>> It is better to have this information passed as device_data and via DT it can
>>>>>>>> be decided based on the compatible property for the device.
>>>>>>> 
>>>>>>> That's not really the problem here - the problem is that the APIs used
>>>>>>> to get the SRAM are DaVinci only so it's not possible to build on OMAP
>>>>>>> or other platforms.  The SRAM code needs to move to a standard API.
>>>>>> 
>>>>>> What about following Matt Porter's idea and ignore the SRAM code
>>>>>> entirely and port the entire PCM code to generic dmaengine code first?
>>>>>> The EDMA driver needs to learn support for cyclic DMA for that, and I
>>>>>> might give that a try in near future.
>>>>>> 
>>>>>> Later on, the SRAM ping-pong code can get added back using genalloc
>>>>>> functions, as Sekhar proposed. That needs to be done by someone who has
>>>>>> access to a Davinci board though, I only have a AM33xx/OMAP here.
>>>>> 
>>>>> We cannot "get rid" of SRAM code and add it back "later". It is required
>>>>> for most DaVinci parts. The SRAM code can be converted to use genalloc
>>>>> (conversion should be straightforward and I can help test it) and the
>>>>> code that uses SRAM can probably keep using the private EDMA API till
>>>>> the dmaengine EDMA driver has cyclic DMA support. Matt has already
>>>>> posted patches to move private EDMA APIs to a common location. That
>>>>> should keep AM335x build from breaking. Is this something that is feasible?
>>>> 
>>>> Yes - by "later" I just meant in a subsequent patch. But you're probably
>>>> right, we can also do that first.
>>>> 
>>>> I'm looking at that right now and the problem seems that we don't have a
>>>> sane way to dynamically look up gen_pools independently of the actual
>>>> run-time platform. All users of gen_pools seem to know which platform
>>>> they run on and access a platform-specific pool. So I don't currently
>>>> see how we could implement multi-platform code, gen_pools are fine but
>>>> don't solve the problem here.
>>>> 
>>>> Would it be an idea to add a char* member to gen_pools and a function
>>>> that can be used to dynamically look it up again? If a buffer with a
>>>> certain name exists, we can use it and install that ping-pong buffer,
>>>> otherwise we just don't. While that would be easy to do, it's a
>>>> tree-wide change.
>>>> 
>>>> Is there a better way that I miss?
>>> 
>>> At the high level there's two platform models we have to handle, the
>>> boot from board file !DT case, and then the boot from DT case. Since
>>> Davinci is just starting DT conversion, we mostly care about the !DT
>>> base in which the struct gen_pool * is passed in pdata to the ASoC
>>> driver. It is then selectable on a per-platform basis where the decision
>>> should be made.
>>> 
>>> Given a separate discussion with Sekhar, we're only going to have one
>>> SRAM pool on any DaVinci part right now...this was only a question on
>>> L138 anyway. But regardless, the created gen_pool will be passed via
>>> pdata.
>> 
>> I thought about this too, as mmp does it that way.
>> 
>>> Since DT conversion is starting and we need to consider that now,
>>> the idea there is to use the DT-based generic sram driver [1] such that
>>> when we do boot from DT on Davinci, the genpool is provided via phandle
>>> and the pointer extracted with the OF helpers that are part of the
>>> series.
>> 
>> A phandle is the cleanest way I think, yes.
>> 
>>> That's pretty much it. I'm reworking the backend support as discussed
>>> with Sekhar wrt to my uio_pruss series. I can post a standalone series
>>> that just replaces sram_* with genalloc for davinci ASoC.
>> 
>> As you can also test it, it would be easiest if you came up with a patch
>> for that, yes. I can have a look at the dma bits laters, once my OMAP
>> board finally works with the code as it currently stands. I'm still
>> fighting with the mcasp driver right now ...
> 
> I quickly prepared two patches to change that, so that topic is out of
> the way. But I did only compile-test them on OMAP - could you check on
> your Davinci platform? Note that these apply on top of the patch in
> discussion here (which isn't applied to the asoc tree yet).

I put a series together yesterday, just ran out of time to post
last night after testing. I'm posting that now...it's on top of my
uio_pruss/genalloc series and only addresss switching davinci-pcm to
genalloc (and actually enabling ping-pon from sram).

I'll take a look a your OMAP patches.

-Matt