On Tue, 2010-08-10 at 14:47 +0100, Mark Brown wrote:
On Tue, Aug 10, 2010 at 03:38:18PM +0200, Sascha Hauer wrote:
I'm wondering what exactly a snd_soc_platform is. Apparently the snd_pcm_ops/pcm_new/pcm_free are specific to a platform. For my understanding these operations are more specific to a cpu_dai. Looking at the tree it seems that each cpu_dai has exactly one possible platform, which seems logical to me because the cpu_dai knows how to transfer the data.
They're for the DMA bit of the CPU. While most platforms have a single DMA controller (though some have more than one) it's moderately common to have more than one DAI (eg, dedicated I2S and DSP mode controllers rather than a programmable serial port, or an AC'97 controller) so it's useful to share the DMA code.
My problem on i.MX is that I currently have two possible cpu dais (imx-ssi.[01]) and each can be configured to use dma or fiq depending on the dma capabilities. So the cpu_dai knows which pcm_ops we have to use, but currently it's the soc glue code which has to decide in platform_name. Am I understanding something wrong here?
This is mostly a holdover from the existing (current mainline) ASoC structuring at the minute, that also has the DMA configured per machine. This may change depending on future hardware requirements, though. _______________________________________________
With multi-component it's possible to register both FIQ and DMA platform together. i.e. ssi0 could use DMA and ssi1 FIQ.
So for OMAP4 I have two platforms. One is the SDMA driver and the other a DSP. So I could have the following DAI link :-
static struct snd_soc_dai_link sdp4430_dai[] = { .name = "TWL6040-SDMA", .stream_name = "TWL6040", .cpu_dai_name ="omap-mcpdm-dai", .codec_dai_name = "twl6040-hifi", .platform_name = "omap-pcm-audio", <<<< SDMA audio device .codec_name = "twl6040-codec", .init = sdp4430_twl6040_init, .ops = &sdp4430_ops, }, { .name = "TWL6040-DSP", .stream_name = "TWL6040", .cpu_dai_name ="omap-mcpdm-dai", .codec_dai_name = "twl6040-hifi", .platform_name = "omap-dsp-audio", <<< DSP audio device. .codec_name = "twl6040-codec", .init = sdp4430_twl6040_init, .ops = &sdp4430_ops, };
The snd_soc_dai_set_dma_data() can be used to pass DMA type data between the SSI ports and FIQ/SDMA components.
Liam