Re: [PATCH v3 2/2] dt-bindings: rtc: m41t80: Mark the clock: subnode as deprecated

[Marek Vasut <marex@denx.de>]

On 12/15/22 19:06, Sebastian Reichel wrote:
> Hi,

Hi,

> On Sun, Dec 11, 2022 at 09:51:24PM +0100, Marek Vasut wrote:
>> The clock {} subnode seems like it is describing an always-on clock
>> generated by the PMIC. This should rather be modeled by consumer of
>> the clock taking phandle to the RTC node itself, since it already
>> does have clock-cells and all. Since there are no users of the clock
>> subnode in tree anyway, mark it as deprecated to avoid proliferation
>> of this approach.
>>
>> Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
>> Signed-off-by: Marek Vasut <marex@denx.de>
>> ---
>> Cc: Alessandro Zummo <a.zummo@towertech.it>
>> Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
>> Cc: Rob Herring <robh+dt@kernel.org>
>> Cc: Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>
>> Cc: linux-rtc@vger.kernel.org
>> To: devicetree@vger.kernel.org
>> ---
>> V2: - Add AB from Krzysztof
>> V3: - No change
>> ---
> 
> I just noticed this by accident. Basically everything in the patch
> description is wrong:
> 
> 1. There is a in-tree user: arch/arm/boot/dts/imx6dl-qmx6.dtsi

Sorry, I missed this one.

> 2. The PMIC has nothing to do with this

In [3] the commit message claims the PMIC supplies 32kHz clock to i.MX6 
CKIL , which per IMX6DQRM rev.6 Table 18-3 row SNVS indirectly supplies 
SNVS RTC . This reminded me of commit:

9509593f327ac ("arm64: dts: imx8mm: Model PMIC to SNVS RTC clock path on 
Data Modul i.MX8M Mini eDM SBC")

which solves exactly the same problem, system hangs when 32 kHz clock 
are stopped, except this time on i.MX8MM, clock are generated by PMIC on 
I2C (notice how the PMIC is referenced directly) and the clock are 
supplied to the SVNS RTC XTal terminals.

I wonder if this could be reused on the QMX6 board too ?

> 3. Directly referencing the RTC does not work, since that introduces
>     an unsolvable dependency loop on QMX6. This was the solution accepted
>     by Rob and Saravana:
> 
> [v1] https://lore.kernel.org/lkml/20210222171247.97609-1-sebastian.reichel@collabora.com/
> [v2] https://lore.kernel.org/all/20210428222953.235280-1-sebastian.reichel@collabora.com/

[3] 
https://lore.kernel.org/linux-clk/20191108170135.9053-1-sebastian.reichel@collabora.com/