Hi, Rob

On 2019/12/19 4:34, Rob Herring wrote:

On Wed, Dec 18, 2019 at 03:37:49PM +0800, Xingyu Chen wrote:

quoted

Hi, Guenter Martin

On 2019/12/16 21:30, Guenter Roeck wrote:

quoted

On 12/15/19 10:03 PM, Xingyu Chen wrote:

quoted

Hi, Martin

Sorry for the late reply.

On 2019/12/13 4:05, Martin Blumenstingl wrote:

quoted

Hi Xingyu and Rob,

On Thu, Dec 12, 2019 at 1:20 PM Xingyu Chen
[off-list ref] wrote:
[...]

quoted

+examples:
+  - |
+    watchdog {
+          compatible = "amlogic,meson-sec-wdt";
+          timeout-sec = <60>;
+    };

in v3 of this patch Rob commented that there shouldn't be an OF node
if there are no additional properties
with timeout-sec there's now an additional property so my
understanding is that it's fine to have an OF node

Your understanding is correct.

quoted

what I don't understand yet is where this node should be placed.
is it supposed to be a child node of the secure monitor node (for
which we already have a binding here:
Documentation/devicetree/bindings/firmware/meson/meson_sm.txt) or
where else would we place it inside the .dts?

IMO,  Although the watchdog node need to reference the meson_sm
node, there is no
bus-like dependencies between the devices which the two nodes
corresponding to.
so i think that the watchdog node as child node of meson_sm maybe
not appropriate.

The watchdog driver needs the meson SM's dt node, and it depends on the
existence
of that node. That seems enough of a relationship to warrant having it
as child note.

Thanks for your reply, if i take the wdt node as child of secure monitor
(sm), how should
i register or find the wdt device ?

I only think of the following three methods :
1). update the sm driver，and scan&register wdt device when the sm driver
probes(It is like i2c), but there
are too many changes involved.

Just add of_platform_default_populate() call and clean-up calls. That's
not what I'd call 'too many changes'.

Thanks for your guidance.

quoted

2). add "simple-bus" key string to compatible of sm node, and it will make
the child node is registered as
platform device, but it seems that the key string is not match current
scene.

You previously said it's not a bus...

quoted

secure-monitor {
     compatible = "amlogic,meson-gxbb-sm",  "simple-bus";

     watchdog {
         compatible = "amlogic,meson-sec-wdt";
         timeout-sec = <60>;
     }
}

3).  don't register device, and find directly the watchdog node by using the
of_* API in watchdog
driver (Eg: linux-4.x/drivers/tee/optee/core.c)

secure-monitor {
     compatible = "amlogic,meson-gxbb-sm";

     watchdog {
         compatible = "amlogic,meson-sec-wdt";
         timeout-sec = <60>;
     }
}

The method 3 looks better for me, do you have a better suggestion ? Thanks

BR

quoted

Guenter

.

.

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