Hi Matti,

On 11/01/2021 11:32, Vaittinen, Matti wrote:

Hello Matthias & All,

On Mon, 2021-01-11 at 11:08 +0100, Matthias Brugger wrote:

quoted

On 11/01/2021 03:18, gene_chen(陳俊宇) wrote:

quoted

[ Internal Use - External ]

Please don't top-post in the future.

quoted

Hi Matthias,

I discussed OF match table with Mark in previous mail in our PATCH
v3,
MFD should just instantiate the platform device.

Did you ever test that? Which MFD driver should instantiate the
device?
I had a look at mt6360-core.c (the obvious one) but I don't see any
reference to
the regulator [1]. What am I missing?

quoted

quoted

Mark Brown [off-list ref] 於 2020年8月20日 週四 下午7:45寫道：

quoted

This device only exists in the context of a single parent
device, there
should be no need for a compatible string here - this is just a
detail
of how Linux does things.  The MFD should just instntiate the
platform
device.

Trying to autoload module without of_id_table will cause run-time 
error:
ueventd: LoadWithAliases was unable to load
of:NregulatorT(null)Cmediatek,mt6360-regulator

You shouldn't have this described in the device tree at all, like I
say
the MFD should just instantiate the platform device.

Well from my understanding the regulator has a device-tree entry [2],
so it
needs to match against a device-tree node. My understanding is, that
you need a
the devicetree node to describe the regulators provided by the
device. TBH I'm a
bit puzzled about the comment from Mark here. How does another DT
node be able
to reference a regulator if this is not described in DT? I think we
need a DT
node here and the matching in the regulator and MFD driver to get the
regulator
loaded via udev.

Others are better to answer - but as I spotted this from my inbox I'll
give my 2 cents :) 

This can be done W/O regulators having own compatible. Please see
following:

drivers/mfd/rohm-bd718x7.c
drivers/regulator/bd718x7-regulator.c
Documentation/devicetree/bindings/mfd/rohm,bd71847-pmic.yaml
Documentation/devicetree/bindings/regulator/rohm,bd71847-regulator.yaml

as example.

Thanks for the links. Yes that's' a way to go, but...

The device matching can be done via platform_device_id table.
I think the MODULE_ALIAS() is needed for module matching - but I don't
remember without further code browsing.

Anyways, the BD71837/47/50 DT entry without compatible for
clk/regulators do probe and load the sub-devices.

As a "tradeoff" subdevices must retrieve the DT node from the parent
device.

For my uneducated eyes the DT binding for regulators should be changed.
Compatible should not be required and the example node should be moved
to MFD binding document in the MFD node. But that's just my view on
this - not willing to push this to any direction!

Generally speaking, DT bindings are stable and can't be changed in a
none-compatible way. We could argue if there is any user of the compatible out
there (probably there isn't any, as the code seems to not even be working).
Apart from that all other cells in the MFD driver are defined as OF_MFD_CELL
[1]. Actually I suspect that mt6360_ldo should represent mt6360-regulator.

Regards,
Matthias

[1] https://elixir.bootlin.com/linux/latest/source/drivers/mfd/mt6360-core.c#L294

Best Regards
	Matti Vaittinen

--
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland
SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~

Simon says - in Latin please.
"non cogito me" dixit Rene Descarte, deinde evanescavit

(Thanks for the translation Simon)

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