On Tue, Jun 9, 2009 at 11:58 AM, Mark Brown<broonie@xxxxxxxxxxxxxxxxxxxxxxxxxxx> wrote: > On Tue, Jun 09, 2009 at 05:39:18PM +0800, Eric Miao wrote: > >> OK, not having enough time to read all this thread, let's make sure >> first we are on the same floor: > >> frame_width = number of bit clocks per frame >> sample_width = number of bits per sample > > Yes. > >> And the assumption that > >> frame_width = sample_width * channel ( = LRCLK for I2S ) > >> is no longer (and ever) correct. > > Ish. That's always been a minimum for most frame formats, though with > programmable ports like the PXA SSP ports I2S normally makes it an exact > requirement. At the minute the magician is abusing a low frame width to > produce a double rate frame clock but this is an abuse. > >> And the TDM mode is actually special for PXA-SSP to emulate the I2S >> protocol, it's no way generic TDM in a common sense. So talking about >> set_tdm_slots(), I'd really like to hide into the format setting code >> of I2S/Left_J to avoid further confusion. > > In terms of the ASoC APIs TDM mode should only be required in order to > configure actual TDM. Ideally the PXA driver should only ever require > set_tdm_slot() for actual TDM configurations and setting up a single > slot for TDM should be equivalent to never having called it at all. > > It's use in the PXA code has always been a wart. > >> And I still didn't quite capture the issue of magician. Phillip, do >> you have any HW reference to the audio codec and the connection on >> magician? > > Essentially his hardware ends up requiring one frame clock per sample in > a stereo stream - ie, a double rate frame clock. I strongly expect that > it is actually running in a DSP mode with one frame sync per sample > rather than per frame. Correct. A flip-flop between the PXA frame clock output and the UDA1380 codec's LRCLK input turns the double rate DSP mode pulses into an I2S style LRCLK signal. I don't have any references for this, but the behaviour is consistent (for example L/R channels are switched if I restart playback after sending an odd number of samples without powering down first) and suitable flip-flops appear in the HTC Blueangel list of parts at http://www2.electronicproducts.com/HTC_XDA_III_Pocket_PC_Phone_-whatsinside-42.aspx. regards Philipp _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
