Hi again
Allright.. Took me forever doing a bisect in alsa-kmirror while finding the proper revision in alsa-drivers to be able to compile it. So painful.. How do you guys ever manage to quickly do bisect ???
Anyhow...
What broke passthrough for me (and others) is this commit:
commit 1ca3d59d5a3e762fb1c002bcd912914bc858b430 Author: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Date: Thu Aug 4 10:12:56 2011 -0500
ALSA: hda: option to enable arbitrary buffer/period sizes
Add new parameter to disable rounding of buffer/period sizes to multiples of 128 bytes. This is more efficient in terms of memory access but isn't required by the HDA spec and prevents users from specifying exact period/buffer sizes. For example for 44.1kHz, a period size set to 20ms will be rounded to 19.59ms.
Tested and enabled on Intel HDA controllers. Option is disabled by default for other controllers.
Tested-by: Wu Fengguang fengguang.wu@intel.com Signed-off-by: Pierre-Louis Bossart pierre-louis.bossart@linux.intel.com Signed-off-by: Takashi Iwai tiwai@suse.de Signed-off-by: Jaroslav Kysela perex@perex.cz
It's not an obvious breakage however and it only occurs with specific combinations of hardware buffer size (as seen for me in /proc/asound/card1/pcm3p/sub0/prealloc) and request of buffer time and period size.
With the default ALSA hardware buffer size of 64kB, AC3/DTS works. With 4096, it doesn't and it will make the tested applications hang.
both MythTV and mplayer (and I know of a few others), request by default a buffer time of 500ms with a period of 4 (requested respectively through snd_pcm_hw_params_set_buffer_time_near and snd_pcm_hw_params_set_periods_near)
With those combinations: (4MB hardware buffer, 500ms and period of 4), trying to write audio with snd_pcm_writei will hang to eventually fail with the error "Input/output error"
Disabling the functionality introduced in that changeset, fix it for v1.0.25 (using the following patch: diff --git a/pci/hda/hda_intel.c b/pci/hda/hda_intel.c index 9cbde2f..9227389 100644 --- a/pci/hda/hda_intel.c +++ b/pci/hda/hda_intel.c @@ -2773,8 +2773,8 @@ static int __devinit azx_create(struct snd_card *card, str }
/* disable buffer size rounding to 128-byte multiples if supported */ - if (chip->driver_caps & AZX_DCAPS_BUFSIZE) - align_buffer_size = 0; +// if (chip->driver_caps & AZX_DCAPS_BUFSIZE) +// align_buffer_size = 0;
/* allow 64bit DMA address if supported by H/W */ if ((gcap & ICH6_GCAP_64OK) && !pci_set_dma_mask(pci, DMA_BIT_MASK(64)))
)
Hope this help Regards Jean-Yves Avenard