[PATCH] arm64: dts: imx8mm: Model PMIC to SNVS RTC clock path on Data Modul i.MX8M Mini eDM SBC

[Marek Vasut]

On 9/27/22 22:23, Tim Harvey wrote:
> On Tue, Sep 27, 2022 at 1:10 PM Marek Vasut <marex at denx.de> wrote:
>>
>> On 9/27/22 21:43, Tim Harvey wrote:
>>
>> Tim,
>>
>>> Marek,
>>>
>>> The modeling here makes sense, but I tried this on the boards I have
>>> with the rohm,bd71847 and it did not bump the clk_enable_count for
>>> clk-32k-out and thus drivers/clk/clk-bd718x7.c still disables the
>>> clock. Is something else required to make that happen?
>>
>> The only thing I can think of is, do you have SNVS_RTC driver enabled
>> and compiled in, just like the PMIC, or are they maybe modules ?
>>
>> You can always try and add a printk() into the snvs rtc driver and see
>> whether the clk_get there doesn't fail for some reason, and what the
>> error code is.
> 
> Marek,

Tim,

> Thanks! I did 'not' have CONFIG_RTC_DRV_SNVS enabled in this test case
> and as soon as I enable that it does bump the count and enable the
> clock. We actually have a separate watchdog on our boards so I
> typically disable the SNVS one to avoid the confusion of having two
> watchdogs for our users. I tried adding 'clocks = <&pmic>' to the wdog
> node and disalbing the RTC_DRV_SNVS again but it fails to enable that
> clock.

I believe the 32 kHz fed into the SNVS RTC are mandatory, they must be 
supplied to the MX8M otherwise the SoC hangs. So whatever supplies the 
RTC_XTALI on your board should be connected to the SNVS RTC node clock 
and the SNVS RTC should be enabled.

> Also I wonder if your patch deserves a 'Fixes: acb01032e11a5 ("arm64:
> defconfig: Enable clock driver for ROHM BD718x7 PMIC")' tag?

No, since the current board DT without this patch is not really broken. 
Without the clock parts in the PMIC node, the PMIC just supplies 32 kHz 
clock and does not disable those clock, because Linux is not even aware 
of them, so everything works just fine even if the PMIC driver is 
enabled. This could potentially by a Fixes for this specific board DT, 
but I am don't think it's worth it either.

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