ti_scm_syscon driver

[Oskar Holmlund]

Den måndag 7 september 2020 02:30:57 CEST, Thomas Skibo <thomas-bsd at skibo.net> skrev: 

Hello.

I am testing some code I have developed to provide the Zynq boards with
a real clock driver and update the other device drivers to use the clock
infrastructure.  It is also supposed to allow us to use "upstream" gnu
dts files.  But, I ran into a problem booting a GENERIC kernel on my Zybo.
The ti_scm_syscon driver, which has the "syscon" compatibility string,
grabs the zynq-slcr node before my driver.  The compatibility property
for the node in the GNU dts file is;

    compatible = "xlnx,zynq-slcr", "syscon", "simple-mfd";

I fixed the problem by having my probe routine return DEVICE_PROBE_SPECIFIC.
But, the DEVICE_PROBE(9) man page seems to say I shouldn't do this.  Also, I
see a lot of device nodes in other boards that have "syscon" along with their
more specific driver name.  Aren't they going to run into problems too if
the ti_scm_syscon driver matches them?  Should the ti_scm_syscon driver use
a lower priority return value in its probe routine?

--Thomas Skibo

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Hi Thomas,

I'm sorry I've caused you trouble with ti_scm_syscon.c catchall for syscon.

I will try to point out the situation from TI dts.
(head) sys/gnu/dts/arm/am33xx-l4.dtsi from line 270 the control module are defined and 286 the syscon part.
The Control module are described here
https://www.kernel.org/doc/Documentation/devicetree/bindings/arm/omap/ctrl.txt
the syscon part is not directly documented for TI its just there in the example.
(of course this exist https://www.kernel.org/doc/Documentation/devicetree/bindings/mfd/syscon.txt )

I'm glad for any suggestions to solve the issue to not interfere with other drivers.
I can test your proposal to lower the priority.
Or get TI to change syscon to something more specific in the DTS?
Maybe its better if i hardcode ti_scm.c to add the syscon child and remove the probe part from ti_scm_syscon.c?
Other suggestions?

--
Bästa Hälsningar
Oskar Holmlund
Tel 070-3220292