Re: [PATCH 1/2] rtc: sun6i: Make external 32k oscillator optional

Jernej Škrabec
2020-02-14T16:42:28Z

Hi Maxime,

Dne petek, 14. februar 2020 ob 09:14:43 CET je Maxime Ripard napisal(a):
> Hi Jernej,
>
> Thanks for taking care of this
>
> On Thu, Feb 13, 2020 at 10:14:26PM +0100, Jernej Skrabec wrote:
> > Some boards, like OrangePi PC2 (H5), OrangePi Plus 2E (H3) and Tanix TX6
> > (H6) don't have external 32kHz oscillator. Till H6, it didn't really
> > matter if external oscillator was enabled because HW detected error and
> > fall back to internal one. H6 has same functionality but it's the first
> > SoC which have "auto switch bypass" bit documented and always enabled in
> > driver. This prevents RTC to work correctly if external crystal is not
> > present on board. There are other side effects - all peripherals which
> > depends on this clock also don't work (HDMI CEC for example).
> >
> > Make clocks property optional. If it is present, select external
> > oscillator. If not, stay on internal.
> >
> > Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
> > ---
> >
> > drivers/rtc/rtc-sun6i.c | 14 ++++++--------
> > 1 file changed, 6 insertions(+), 8 deletions(-)
> >
> > diff --git a/drivers/rtc/rtc-sun6i.c b/drivers/rtc/rtc-sun6i.c
> > index 852f5f3b3592..538cf7e19034 100644
> > --- a/drivers/rtc/rtc-sun6i.c
> > +++ b/drivers/rtc/rtc-sun6i.c
> > @@ -250,19 +250,17 @@ static void __init sun6i_rtc_clk_init(struct
> > device_node *node,>
> > writel(reg, rtc->base + SUN6I_LOSC_CTRL);
> >
> > }
> >
> > - /* Switch to the external, more precise, oscillator */
> > - reg |= SUN6I_LOSC_CTRL_EXT_OSC;
> > - if (rtc->data->has_losc_en)
> > - reg |= SUN6I_LOSC_CTRL_EXT_LOSC_EN;
> > + /* Switch to the external, more precise, oscillator, if present */
> > + if (of_get_property(node, "clocks", NULL)) {
> > + reg |= SUN6I_LOSC_CTRL_EXT_OSC;
> > + if (rtc->data->has_losc_en)
> > + reg |= SUN6I_LOSC_CTRL_EXT_LOSC_EN;
> > + }
> >
> > writel(reg, rtc->base + SUN6I_LOSC_CTRL);
> >
> > /* Yes, I know, this is ugly. */
> > sun6i_rtc = rtc;
> >
> > - /* Deal with old DTs */
> > - if (!of_get_property(node, "clocks", NULL))
> > - goto err;
> > -
>
> Doesn't that prevent the parents to be properly set if there's an
> external crystal?

No, why?

Check these two clk_summary:
http://ix.io/2bHY Tanix TX6 (no external crystal)
http://ix.io/2bI2 OrangePi 3 (external crystal present)

Please disregard ac200_clk in first case, it's part of another work.

Best regards,
Jernej