On 01/21/2014 09:15 PM, Mark Brown wrote: > On Wed, Jan 15, 2014 at 01:27:21PM +0200, Jyri Sarha wrote: >> On 12/31/2013 03:25 PM, Mark Brown wrote: > >>>> support. The only supported sample format is SNDRV_PCM_FORMAT_S32_LE. >>>> The 8 least significant bits are ignored. > >>> Where does this constraint come from? > >> From driver/gpu/drm/i2c/tda998x_drv.c. The driver configures CTS_N >> register statically to a value that works only with 4 byte samples. >> According to my tests it is possible to support 3 and 2 byte samples >> too by changing the CTS_N register value, but I am not sure if the >> configuration can be changed on the fly. My data sheet of the nxp >> chip is very vague about the register definitions, but I suppose the >> register configures some clock divider on the chip. HDMI supports >> only upto 24bit audio and the data sheet states that any extraneous >> least significant bits are ignored. > > Hrm. This sounds like it ought to be presenting as an ASoC CODEC > driver. >
I do not disagree. I just do no not have a clear understanding how something like that should be done. Either the tda998x_drv it self should provide the ASoC codec driver or there should be some kind of API that could be accessed by some driver under sound/soc/codecs. Anyway it sound like Jean-Francois Moine is already doing that. I'll take his driver into use as soon as his code is merged. However, for now a simple implementation that I have does not really need any interaction with the HDMI encoder and thus no codec driver either. >>>> + snd_pcm_hw_constraint_minmax(runtime, SNDRV_PCM_HW_PARAM_CHANNELS, >>>> + 2, 2); > >>> Why not just set all this statically when registering the DAI? > >> Because there is no relevant DAI to where to put these limitations. >> I did not want to add yet another dummy codec driver, but decided to >> use the already existing ASoC HDMI codec. By default the driver >> support all audio params supported by HDMI. The limitations are >> coming from NXP chip, the NXP driver, and because the chip is used >> in i2s mode. In other words the limitation is coming from machine >> setup, not from the DAIs. > > OK, but it sounds like it's got register configuration as well? That > really does sound like a device that ought to have a driver... > Sure, but it would not save form making runtime constraints. The usage of i2s mode, which limits the number of channels, is selected by dai_fmt call after dai registering. Best regards, Jyri
