On Thu, Jun 09, 2022 at 04:09:57PM +0200, Martin Povišer wrote: > > On 9. 6. 2022, at 15:33, Mark Brown <broonie@xxxxxxxxxx> wrote: > >> + /* > >> + * Primary FE > >> + * > >> + * The mclk/fs ratio at 64 for the primary frontend is important > >> + * to ensure that the headphones codec's idea of left and right > >> + * in a stereo stream over I2S fits in nicely with everyone else's. > >> + * (This is until the headphones codec's driver supports > >> + * set_tdm_slot.) > >> + * > >> + * The low mclk/fs ratio precludes transmitting more than two > >> + * channels over I2S, but that's okay since there is the secondary > >> + * FE for speaker arrays anyway. > >> + */ > >> + .mclk_fs = 64, > >> + }, > > This seems weird - it looks like it's confusing MCLK and the bit clock > > for the audio bus. These are two different clocks. Note that it's very > > common for devices to require a higher MCLK/fs ratio to deliver the best > > audio performance, 256fs is standard. > On these machines we are not producing any other clock for the codecs > besides the bit clock, so I am using MCLK interchangeably for it. (It is > what the sample rate is derived from after all.) Please don't do this, you're just making everything needlessly hard to understand by using standard terminology inappropriately and there's a risk of breakage further down the line with drivers implementing the standard ops. > One of the codec drivers this is to be used with (cs42l42) expects to be > given the I2S bit clock with > snd_soc_dai_set_sysclk(dai, 0, mclk, SND_SOC_CLOCK_IN); That's very, very non-standard... > I can rename mclk to bclk in all of the code to make it clearer maybe. > Also the platform driver can take the bit clock value from set_bclk_ratio, > instead of set_sysclk from where it takes it now. The cs42l42 driver I can > patch too to accept set_bclk_ratio. ...indeed, set_bclk_ratio() is a better interface for setting the bclk ratio - the CODEC driver should really be doing that as well. > > This shouldn't be open coded in a driver, please factor it out into the > > core so we've got an API for "set limit X on control Y" then call that. > There’s already snd_soc_limit_volume, but it takes a fixed control name. > Can I extend it to understand patterns beginning with a wildcard, like > '* Amp Gain Volume’? Or add a new call that does that.
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