Re: [PATCH 09/15] ASoC: SDCA: Add UMP buffer helper functions

[Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxx>]

On Thu, Sep 11, 2025 at 02:33:46PM +0200, Pierre-Louis Bossart wrote:
> > Once these timeouts exist we have to pick values for them,
> > because SDCA is a huge huge fan of asking you to wait for
> > something but not saying for how long. If you have any thoughts
> > on this that would be appreciated too, but mostly I will just
> > pluck some vaguely reasonable sounding values as I did for the
> > existing FDL timeouts.
> 
> The SDCA 1.0 spec defines DisCo properties for UMP timeouts,
> just do a search for "ownership-transition-max-delay". Table 139
> page 236 defines this property specifically for XUs and hence
> the low-level protocol FDL is based on.
> 
> The description reads:
> 
> "
> The maximum time allowed for Device to change the
> ownership from Device to Host in an Rx UMP when Host
> Software is waiting for the owner to change back to Host.
> "
> 
> As usual it's quite possible that platform firmware is broken
> with bad values, but the design intent was to provide a timeout
> value for software to use. Ignoring these properties doesn't
> seem quite right to me...

No, I had missed this property! That is excellent. Don't suppose
you have a similar magic touch with the "Wait until there are
no new requests for File Download" in the Class Software Load
Sequence?

Thanks,
Charles