lkml.org 
[lkml]   [2019]   [Aug]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [linux-sunxi] [PATCH v2 2/3] rtc: sun6i: Add support for H6 RTC
Hello Jernej,

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

> >
> > 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
>
> > regards,
> > o.
> >
> > > > 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
> > >
> > > > regards,
> > > >
> > > > o.
>
>
>
>

\
 
 \ /
  Last update: 2019-08-24 23:28    [W:0.053 / U:16.944 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site