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

Daniel Mack zonque at gmail.com
Thu Oct 4 13:11:17 CEST 2012

On 04.10.2012 12:28, Matt Porter wrote:
> On Thu, Oct 04, 2012 at 11:57:30AM +0200, Daniel Mack wrote:
>> On 04.10.2012 11:38, Porter, Matt wrote:
>>> 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).
>> Ok, I don't care which version makes it in after all :)
> Ok :)
>>> I'll take a look a your OMAP patches.
>> The patches I just sent out are only for Davinci and change the SRAM
>> functions to genalloc in the mcasp driver. They work just fine on OMAP
>> of course, as the code is disabled in there.
> Ok, same thing as I did and just sent out. These are tested on AM180x
> and hook up ping-pong buffering so that there's actually one user of
> all this ping-pong code. It's been sitting idle for a long time.
> I didn't see your patches come by yet but will take a look to see if
> we need to combine.

I attached them to my mail for a quick review. I wanted to queue them up
to a bigger series I'll send out later ...


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