Hello Takashi, I called the function snd_pcm_lib_preallocate_pages_for_all passing SNDRV_DMA_TYPE_DEV and pointer to struct device as parameters. This doesn't crash. However with SNDRV_DMA_TYPE_CONTINUOUS it did crash. I have used the function "snd_pcm_lib_malloc_pages" in the hw_params callout to allocate DMA memory. I hope this is the right way of doing the DMA allocation. With this above configuration can I stay assured that "dma_addr" will give me the physical address of the buffer? Regards; Aadish On Thu, Jun 24, 2010 at 1:57 PM, Adish Kuvelker <adkuvi@xxxxxxxxx> wrote: > Hello Takashi, > > I'm sorry as this is getting bit confusing for me. Playing the PCM > data I would want to pass the starting physical address of this > location to the DMA start address. Now can I access "dma_addr" > directly for this purpose? > Do I still have to allocate DMA memory or will just passing of this > dma_addr as source address suffice? > > I am new to ALSA framework and it's getting a bit confusing to me. > > Regards; > Aadish > > On Thu, Jun 24, 2010 at 1:14 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: >> At Thu, 24 Jun 2010 12:52:47 +0530, >> Adish Kuvelker wrote: >>> >>> Hello, >>> >>> If I use "SNDRV_DMA_TYPE_CONTINUOUS" as a parameter to pre-allocate >>> function to get contiguous locations of memory and use the function >>> snd_dma_continuous_data() would that be correct setting for my case? >> >> I guess no. As mentioned, it's no DMA memory, i.e. simple pages >> allocated via __get_free_pages() and co. >> >>> Where are the parameters of dma_addr and dma_area written to the >>> runtime structure? >> >> These are available only for pages properly allocated for DMA. >> >> >> Takashi >> >>> >>> Regards; >>> Aadish >>> >>> On Thu, Jun 24, 2010 at 12:45 PM, Takashi Iwai <tiwai@xxxxxxx> wrote: >>> > At Thu, 24 Jun 2010 12:38:35 +0530, >>> > Adish Kuvelker wrote: >>> >> >>> >> Hello Takashi, >>> >> >>> >> I am developing a DMA Controller driver to service the PCM out data to >>> >> the Audio controller on the arm-based ATLASIII procesor. In case you >>> >> need any more information on the architecture I can pass. >>> >> >>> >> Since the DMA isn't on PCI bus I am pre-allocation continuous memero >>> >> using the "snd_pcm_lib_preallocate_pages_for_all" passing >>> >> SNDDRV_DMA_TYPE_DEV and "snd_dma_continuous_data" as appropriate >>> >> parameters. >>> > >>> > snd_dma_continuous_data() is only for SNDRV_DMA_TYPE_CONTINUOUS. >>> > In this case, the pages aren't for DMA. >>> > >>> > For SNDRV_DMA_TYPE_DEV, simply pass the device pointer you use. >>> > >>> > >>> > Takashi >>> > >>> >> > _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
