Re: [PATCH v3 2/9] ARM: dts: nspire: Use syscon-reboot to handle restart

From: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
To: Andrew Davis <afd@ti.com>, Lee Jones <lee@kernel.org>,
	Rob Herring <robh+dt@kernel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
	Arnd Bergmann <arnd@arndb.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	Geert Uytterhoeven <geert+renesas@glider.be>,
	Daniel Tang <dt.tangr@gmail.com>,
	Fabian Vogt <fabian@ritter-vogt.de>
Cc: devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 2/9] ARM: dts: nspire: Use syscon-reboot to handle restart
Date: Thu, 27 Oct 2022 17:27:09 -0400	[thread overview]
Message-ID: <4236ab07-6ad3-efcd-7d5e-c244581d2944@linaro.org> (raw)
In-Reply-To: <a4688f2d-0a0f-dffc-92cc-4fa50938d0d8@ti.com>

On 27/10/2022 17:07, Andrew Davis wrote:
> On 10/27/22 2:33 PM, Krzysztof Kozlowski wrote:
>> On 27/10/2022 14:13, Andrew Davis wrote:
>>> Writing this bit can be handled by the syscon-reboot driver.
>>> Add this node to DT.
>>>
>>> Signed-off-by: Andrew Davis <afd@ti.com>
>>> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
>>> Tested-by: Fabian Vogt <fabian@ritter-vogt.de>
>>> Reviewed-by: Fabian Vogt <fabian@ritter-vogt.de>
>>> ---
>>>   arch/arm/boot/dts/nspire.dtsi | 7 +++++++
>>>   1 file changed, 7 insertions(+)
>>>
>>> diff --git a/arch/arm/boot/dts/nspire.dtsi b/arch/arm/boot/dts/nspire.dtsi
>>> index bb240e6a3a6f..48fbc9d533c3 100644
>>> --- a/arch/arm/boot/dts/nspire.dtsi
>>> +++ b/arch/arm/boot/dts/nspire.dtsi
>>> @@ -172,7 +172,14 @@ rtc: rtc@90090000 {
>>>   			};
>>>   
>>>   			misc: misc@900a0000 {
>>> +				compatible = "ti,nspire-misc", "syscon", "simple-mfd";
>>
>> You have syscon and simple-mfd, but bindings in patch #1 say only syscon.
>>
> 
> I'm not following, are you just saying my wording in the patch message just
> wasn't complete?

Your binding patch adds nspire compatible to the list of two items, so
you have two items in total - nspire followed by syscon.

What you implemented here is different.

> 
> Or are you saying something more about nodes that are both syscon and simple-mfd?
> In that case, having both syscon and simple-mfd seems rather common, looks like
> you added the rule for it[0].
> 
> Thinking on this, they almost represent the same thing. simple-mfd says "my child
> nodes should be considered devices", why do we need that? Couldn't we simply state
> that "syscon" node's children are always devices, I mean what else could they be,
> syscon is an MFD after all (and lives in drivers/mfd/).

No, syscon is not an MFD. Syscon means system controller and alone it
does not have children.

> 
> "syscon" often just says, others can use the registers within this node, so as a
> different option, make "syscon" a property of "simple-mfd" nodes. I'm seeing all
> these examples of devices that should have been children of the "syscon" device,
> but instead use
> 
> regmap = <&x>;
> syscon = <&x>;
> 
> or similar and put the device node out somewhere random. And in those cases,
> wouldn't it have been more correct to use the normal "reg" and "regions" to
> define the registers belonging to the child node/device?..

Sorry, I do not follow. How this is even related to your patch?

Your bindings say A, DTS say B. A != B. This needs fixing.

Unless you are asking me what your device is in general. This I don't
really know, but if you want to use it as regmap provider for system
registers and as a parent of syscon-based reboot device, then your
device is syscon and simple-mfd. With a specific compatible. Was this
your question?

Best regards,
Krzysztof