On Fri, Jul 09, 2021 at 05:05:47PM +0000, Robert Hancock wrote: > On Fri, 2021-07-09 at 13:38 +0100, Mark Brown wrote: > > For something like this I think the driver should be able to figure out > > the ratio based on the configured MCLK and sample rate. For the most > > part set_clkdiv() should be a legacy thing, it's very manual and hard to > > see why a system would do something different to the obvious ratio > > usually. > Possibly the I2S transmitter should be implementing set_sysclk rather than > set_clkdiv then? simple-audio-card seems like it would already propagate that > through into the CPU DAI in asoc_simple_hw_params and then it could figure out > the right divider value to use. I think so. > The tricky part is that the Audio Formatter (used as the "plat" component here) > also needs to know what the mclk-fs value is. (I really don't know why it > cares, I would think it would just push data to the output stream as fast as it > was accepted, but indeed it does have a register to set the sample rate to MCLK > divider, and if it's not set properly the I2S transmitter downstream seems to > constantly get underruns.) I'm not sure if there's any mechanism for it to > determine the value right now, or if something new would need to be added? Given that it knows the MCLK if set_sysclk() is used and it knows the sample rate it should just be able to calculate the ratio?
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