Hello Jernej,

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

quoted

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.

quoted

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.

regards,
	o.

Best regards,
Jernej

quoted

regards,
	o.

quoted

quoted

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-bsp#n
650

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



Best regards,
Jernej

quoted

regards,

	o.

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