On Fri, Jun 02, 2023 at 01:19:08PM +0100, Mark Brown wrote:
On Fri, Jun 02, 2023 at 12:12:52PM +0000, Alvin Šipraga wrote:
On Fri, Jun 02, 2023 at 12:43:51PM +0100, Mark Brown wrote:
Why would we have a property for this and not just describe whatever the actual clocking arrangement is?
Sure - let me just elaborate on my thinking and maybe you can help me with a better approach:
The clocking arrangement is encoded in the dai_fmt field of snd_soc_dai_link, but this is a single value that describes the format on both ends. The current behaviour of ASoC is to flip the clock roles encoded in dai_fmt when applying it to the CPU side of the link.
Looking from a DT perspective, if I do not specify e.g. bitclock-master on either side of the link, then the dai_fmt will describe the codec as a bitclock consumer and (after flipping) the CPU as a provider. That's the default implication of the DT bindings and I can't break compatibility there.
None of this addresses my question. To repeat why would we not just describe the actual clocking arrangement here - this property does not specify where the clock actually comes from at all, we're still going to need additional information for that and if we've described that clock then we already know it's there without having to specify any more properties.
Yes I see what you mean. On my platform the clock source is actually described by the common clock framework, so I would want to use that. If it were a component driver then it would most likely be a codec that is part of the dai-link anyway. So what about having two struct clk pointers in struct snd_soc_dai?
struct snd_soc_dai { /* ... */ struct clk *bitclock_provider; struct clk *frameclock_provider; /* ... */ };
If non-NULL I could then have the ASoC core enable/disable the clocks on demand? I would say in hw_params/hw_free, albeit that runs after set_fmt.
Having said that, I see ASoC doesn't really use the CCF much... am I way off?
I don't think it's feasible to modify every component driver to explicitly handle this and then ignore any CBP_CFP bits set in its call to set_fmt - this is why I want help from the ASoC core.
The other issue is that for the simple-card the DAI format is only parsed in one place and applied to the whole link. Are you proposing that it be modified to explicitly try and parse both ends in order to determine if both sides want to be clock consumers? In that case I'd have to also introduce bitclock-consumer and frameclock-consumer properties to mirror the existing bitclock-master and frameclock-master properties, as an explicit absence of the *-master property on both sides would have to default to the original ASoC behaviour described above.
If simple-card can't be made to work that's fine, it's deprecated anyway.
Ah OK, I didn't know that. Right now I'm using graph-card2, that's not deprecated, right?
Kind regards, Alvin