On Wed, Aug 11, 2021 at 01:21:24PM +0100, Richard Fitzgerald wrote:
On 11/08/2021 12:56, Mark Brown wrote:
On Tue, Aug 10, 2021 at 05:27:45PM +0100, Richard Fitzgerald wrote:
cs42l42_pll_config() could check whether it is already running and skip configuration in that case, but that seems to me a rather opaque implementation. In my opinion this doesn't really fall into the case of ignoring-bad-stuff-to-be-helpful (like free() accepting a NULL).
This doesn't treat the situation as an error though, it just ignores it, and there's nothing to stop _pll_config() generating a warning if that makes sense.
It isn't an error. hw_params() will be called for both substreams (PLAYBACK and CAPTURE) and if one is already running we mustn't reconfigure the things we already configured. The DAI is marked symmetric so both substreams will always produce the same I2C BCLK.
If it's a noop reconfiguration then there's a case for saying that _pll_config() should just silently do nothing anyway regardless of issues with reconfiguring, though you might also want to warn dpeending on other expectations. If it's not a noop reconfiguration then presumably the new configuration not taking effect might mean that other things aren't going to see the clocks they expect. Either way if a reconfiguration gets introduced via a path other than hw_params(), either now or later, having the check in the _pll_config() would catch it.