Re: missing timer in dts: how to deal ?

[Jared McNeill <jmcneill%invisible.ca@localhost>]

Hi Manuel --

The fp_bootstrap callback for i.mx6sx should be able to deal with this. 
Either make a fake device_t + softc and call the attach function directly 
(no need for this to be an actual device), or create a node 
programatically describing the device and add it to the fdt using 
libfdt.h.

Try to make the code smart enough to only do this if a device with that 
compatible string does not already exist in the device tree, in case it is 
added in the future.

HTH,
Jared



On Fri, 5 May 2023, Manuel Bouyer wrote:

> Hello,
> the i.mx6sx SoC I got working recently includes a single-core cortex A9 CPU.
> As I understand it, all A9 CPUs have the TWD timer, and this is what we
> use for delay and hardclock(). But the imx6sx.dtsi file is missing the
> TWD node ("arm,cortex-a9-twd-timer"), while the imx6qdl.dtsi includes it.
>
> How can we deal with this ?
> - add the twd node to our copy of the device tree (this is what I did
>  in my tree but didn't commit it). But this patches a file in sys/external
> - fake a node in the in-memory fdt early in boot (but is there a way to do
>  this ? I couldn't find anything related to fake nodes in dev/fdt/ or
>  dev/ofw/)
> - add a non-fdt attachement for TWD (and need to find where and when to
>  attach it - maybe as a child of
>  cpus0 at simplebus0
>
> Any though from port-arm experts ?
>
> --
> Manuel Bouyer <bouyer%antioche.eu.org@localhost>
>     NetBSD: 26 ans d'experience feront toujours la difference
> --