On Thu, Jun 2, 2016 at 11:40 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Thu, Jun 02, 2016 at 10:40:58AM -0700, Caleb Crome wrote: >> On Thu, Jun 2, 2016 at 10:17 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> > Well, if you specifically mean TDM as opposed to multi-channel our >> > general support for that isn't good (mainly due to lack of demand). It >> > sounds like you're more interested in multi channel here though. > >> I must be missing something. To me, TDM is synonymous with >> multi-channel on a single wire. The datasheets of codecs and SoCs > > TDM, at least in the sense Linux is using it, is multiple *unrelated* > audio streams on a single wire. Any multi-channel audio stream is TDM > in some sense but the trivial extension to add two or more channels > isn't really a big deal. This is for things more complex than just > stuffing more bytes of data onto a wire where there are going to be some > timeslots that the device should ignore as they're going to/from other > devices (or at least other streams even if the same chip is handling > them). Hi Mark, Thanks for taking the time to describe this to me. This definitely comes as a surprise to me. I assumed that TDM mode simply means multi-channels on a single wire (which is what it means in all the datasheets). Just so I have this straight, TDM in the linux sense is putting say, 6-channels on one wire where the channels are from logically different places? i.e. chanels 0-1 are from bluetooth, 2-3 from analog in, and 4-5 from somewhere else? So, going back to Nicolin's original question for this email, the CS53L30, what are the proper DT settings for these modes: The device can be configured in what amounts to at least 3 different modes: 1) 4-channel, 5-pin ADC interface: dual I2S: shared BCLK/WCLK/MCLK, separate data pins for channels 0/1 and 2/3 (SDOUT0/SDOUT1). 2) 4-channel, 4-pin ADC interface: MBLCK/BCLK/WCLK/SDOUT0 only. Slots 0/1/2/3 on the SDOUT0 pin (synch master) 3) and finally, a multi-codec configuration, where 4 x CS53L30 are used: 16-channel, 4-pin ADC (what I call TDM) interface, all on the same 4 pins. These are very related data streams -- they are perfectly synchronized in hardware, so perhaps this isn't TDM in the linux-sense. >> Nicolin Wrote: >> Another question is for its TDM support. This chip outputs 4-channel >> data on two data output pins (SDOUT1 and SDOUT2) as normal mode; it >> outputs 4-channel data on one data output pin (SDOUT1) as TDM mode. >> However, the mode selection for a 4-channel recording should depend >> on the hardware design: whether the SDOUT2 is connected or not. So >> I am wondering if there is a common way or existing way to indicate >> this hardware design. Or just by simply defining a new DT property? As far as I can see he's not trying to define *unrelated* streams in TDM mode, but very related streams, which is TDM in the datasheet-sense. And there not only needs to be a mechanism of choosing the dual I2S mode, but also which TDM slots to drop the data in (which I think already exists, right?) >> What's the linuxy name for what the datasheets call TDM format with >> slots > 2? Do we just call that 'multi-channel', or specifically say, >> 'channels_max > 2'? I was always under the assumption that's what TDM >> meant. > > We don't particularly call it anything, it's such a trivial extension. That's not been my experience :-) Getting 16 channels onto a wire has been anything but trivial because of the lack of SoC driver support for it. Perhaps I'm just using the wrong SoCs. Thanks again, -Caleb _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
