Re: [PATCH 3/5] dt-bindings: reset: ocelot: Add documentation for 'microchip,reset-switch-core' property

[Lars Povlsen <lars.povlsen@microchip.com>]

Lars Povlsen writes:

> Sebastian Reichel writes:
>
>> Hi,
>> 
>> On Tue, Jun 02, 2020 at 11:49:08AM +0200, Lars Povlsen wrote:
>> > Rob Herring writes:
>> > > On Wed, May 13, 2020 at 03:08:40PM +0200, Lars Povlsen wrote:
>> > >> This documents the 'microchip,reset-switch-core' property in the
>> > >> ocelot-reset driver.
>> > >>
>> > >> Signed-off-by: Lars Povlsen <lars.povlsen@microchip.com>
>> > >> ---
>> > >>  .../devicetree/bindings/power/reset/ocelot-reset.txt        | 6 ++++++
>> > >>  1 file changed, 6 insertions(+)
>> > >>
>> > >> diff --git a/Documentation/devicetree/bindings/power/reset/ocelot-rese=
>> t.txt b/Documentation/devicetree/bindings/power/reset/ocelot-reset.txt
>> > >> index 4d530d8154848..20fff03753ad2 100644
>> > >> --- a/Documentation/devicetree/bindings/power/reset/ocelot-reset.txt
>> > >> +++ b/Documentation/devicetree/bindings/power/reset/ocelot-reset.txt
>> > >> @@ -9,9 +9,15 @@ microchip Sparx5 armv8 SoC's.
>> > >>  Required Properties:
>> > >>   - compatible: "mscc,ocelot-chip-reset" or "microchip,sparx5-chip-res=
>> et"
>> > >>
>> > >> +Optional properties:
>> > >> +- microchip,reset-switch-core : Perform a switch core reset at the
>> > >> +  time of driver load. This is may be used to initialize the switch
>> > >> +  core to a known state (before other drivers are loaded).
>> > >
>> > > How do you know when other drivers are loaded? This could be a module
>> > > perhaps. Doesn't seem like something that belongs in DT.
>> > >
>> > 
>> > The reset driver is loaded at postcore_initcall() time, which ensures it
>> > is loaded before other drivers using the switch core. I noticed other
>> > drivers do the same to do low-level system reset and initialization at
>> > early boot time.
>> > 
>> > > Can this behavior be implied with "microchip,sparx5-chip-reset"?
>> > 
>> > Since we need to cater for both modus operandi, I would need two driver
>> > compatible strings per platform, which scales worse than a single
>> > property.
>> > 
>> > The "microchip,reset-switch-core" is a device configuration property
>> > which tells the system (driver) how the hw should be handled. Since you
>> > do not *always* want to reset the switch core (f.ex. when implementing
>> > systems with warm reboot), I think it makes perfect sense - but I may be
>> > biased off course :-)
>> > 
>> > Thank you for (all) of your comments, by the way!
>> > 
>> > ---Lars
>> > > Rob
>> 
>> Is this series still needed? Did I miss a follow-up?
>
> Hi Sebastian!
>
> Yes, the series is still needed, but the conversation died after my
> last message.
>
> If the DT-controlled reset property is too controversial, I am willing
> to drop that part. (Rob just reviewed the bindings).
>
> MCHP reference designs have GPIO resets, so we *could* get by without,
> but new designs may this feature.
>
>> -- Sebastian
>

Sebastian,

Any update on the patches? They're the last part of the original Sparx5
series, so I would love to get them done.

As previously stated, I could remove the "microchip,reset-switch-core"
parts if that's whats what holding it stuck.

---Lars

-- 
Lars Povlsen,
Microchip