Hi Robin,

Am Dienstag, 10. April 2018, 13:18:48 CEST schrieb Robin Murphy:
> On 10/04/18 10:26, Heiko Stuebner wrote:
> > Rockchip IOMMUs are used without explicit clock handling for 4 years
> > now, so we should keep compatibility with old devicetrees if possible.
> > Therefore make iommu clocks optional.
> 
> Do we need to touch the binding itself? Obviously the driver has to 
> treat clocks as optional in existing DTs (and I feel a bit dumb now for 
> managing to overlook that in review), but the binding effectively only 
> covers future DTs, and I'd assume we want to encourage the clocks to be 
> correctly specified there.

I guess that depends on your definition of the timespan for backwards
compatibility. I'm always starting out at indefinite till convinced
otherwise ;-). Hence the clocks would need to stay optional for (nearly)
forever.

Also, having the binding claim them as required but the code handling
them as optional just calls for someone to remove the optional handling :-D

Not sure if there is a established way of saying
"we want this for all future devices, but allow it to be missing for old dts".


Heiko
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