Dne sobota, 24. avgust 2019 ob 23:27:46 CEST je Ondřej Jirman napisal(a):

Hello Jernej,

On Sat, Aug 24, 2019 at 11:09:49PM +0200, Jernej Škrabec wrote:

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Visually?

That would explain why it doesn't work for you. The mainline RTC driver
disables auto-switch feature, and if your board doesn't have a crystal
for
LOSC, RTC will not generate a clock for the RTC.

H6's dtsi describes by default a situatiuon with external 32k crystal
oscillator. See ext_osc32k node. That's incorrect for your board if it
doesn't have the crystal. You need to fix this in the DTS for your board
instead of patching the driver.

I see that reparenting is supported, but I'm not sure how to fix that in
DT. Any suggestion?

You may try removing the clocks property from rtc node.

I don't think this would work:
https://elixir.bootlin.com/linux/latest/source/drivers/rtc/rtc-sun6i.c#L246

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The driver has parent clock selection logic in case the LOSC crystal is
not
used.

Your patch enables automatic detection of LOSC failure and RTC changes
clock to LOSC automatically, despite what's described in the DTS. That
may fix the issue, but is not the correct solution.

Registers on my board look like this (external 32k osc is used) for
reference:

LOSC_CTRL_REG[7000000]: 8011

	KEY_FIELD                      ???                  (0)
	LOSC_AUTO_SWT_BYPASS           EN                   (1)
	LOSC_AUTO_SWT_EN               DIS                  (0)
	EXT_LOSC_EN                    EN                   (1)
	EXT_LOSC_GSM                   LOW                  (0)
	BATTERY_DIR                    DISCHARGE            (0)
	LOSC_SRC_SEL                   EXT32k               (1)

LOSC_AUTO_SWT_STA_REG[7000004]: 1

	EXT_LOSC_STA                   OK                   (0)
	LOSC_AUTO_SWT_PEND             NOEFF                (0)
	LOSC_SRC_SEL_STA               EXT32K               (1)

In my case LOSC_CTRL_REG has value 0x4010 and LOSC_AUTO_SWT_STA_REG
has value 0x4, so there is issue with external crystal (it's missing) and
RTC switched to internal one.

BTW, what's wrong with automatic switching? Why is it disabled?

It always was disabled on mainline (bit 14 was set to 0 even before my
patch). H6 just probably has another extra undocummented bit, that's needed
to disables it properly.

You probably don't want a glitch to switch your RTC from high-precision
clock to a low precision one possibly without any indication in the
userspace or a kernel log.

Regardless of all this, DTS needs to have a correct description of the HW,
which means if RTC module is not connected to the 32.757kHz crystal/clock,
clocks property should be empty.

If we are talking about correct HW description, then clock property should 
actually have possibility that two clocks are defined - one for internal RC 
(always present) and one external crystal (optional). In such case I could 
really just omit external clock and be done with it. But I'm not sure if such 
solution is acceptable at this point.

Best regards,
Jernej

regards,
	o.

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Best regards,
Jernej

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regards,

	o.
	

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The real issue probably is that the mainline driver is missing this:

https://megous.com/git/linux/tree/drivers/rtc/rtc-sunxi.c?h=h6-4.9-b
sp#n
650

Not sure what you mean by that. ext vs. int source selection?



Best regards,
Jernej

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regards,

	o.

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