On Thu, Apr 5, 2018 at 8:51 AM, Robert Jarzmik <robert.jarzmik@xxxxxxx> wrote: > Arnd Bergmann <arnd@xxxxxxxx> writes: > >> I'm still unable to follow through that code, but I understand now that >> the device you pass to dma_request_slave_channel() is not the one >> we'd like it to be here. >> >> Where exactly does that call to dma_request_chan() happen? Is this >> the one in dmaengine_pcm_new()? Could we perhaps put a >> pointer to the SSP device into snd_dmaengine_dai_dma_data? > This is a sample stack I captured with an added WARN_ON(1), triggered by a > userland "aplay Sultans_Of_Swing.wav" :) > > [ 299.216743] [<c0012e80>] (unwind_backtrace) from [<c000f55c>] (show_stack+0x20/0x24) > [ 299.223986] [<c000f55c>] (show_stack) from [<c0529d68>] (dump_stack+0x20/0x28) > [ 299.231321] [<c0529d68>] (dump_stack) from [<c001de34>] (__warn+0xf0/0x11c) > [ 299.238183] [<c001de34>] (__warn) from [<c001df94>] (warn_slowpath_null+0x4c/0x58) > [ 299.245234] [<c001df94>] (warn_slowpath_null) from [<c02a2d38>] (dma_request_chan+0x40/0x228) > [ 299.252550] [<c02a2d38>] (dma_request_chan) from [<c02a2f38>] (dma_request_slave_channel+0x18/0x24) > [ 299.259855] [<c02a2f38>] (dma_request_slave_channel) from [<c03f76f0>] (__pxa2xx_pcm_open+0xf4/0x110) > [ 299.266789] [<c03f76f0>] (__pxa2xx_pcm_open) from [<c0409ed0>] (soc_pcm_open+0xf8/0x9c8) > [ 299.273932] [<c0409ed0>] (soc_pcm_open) from [<c03db9d4>] (snd_pcm_open_substream+0x9c/0x134) Ok, so it seems we currently have a special case here that is only used by pxa/mmp and omap, and you can simply open-code that by calling dma_request_chan() from the pxa-specific __pxa2xx_pcm_open() with any device pointer you like, it doesn't have to be the main audio device. I don't know exactly how the probing works, but I'd assume that we have the correct device pointers in pxa2xx_ac97_dev_probe() and asoc_ssp_probe(), or maybe in pxa2xx_ac97_*_startup() and pxa_ssp_startup(). Arnd _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel