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

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Date:   Fri, 14 Feb 2020 09:14:43 +0100
From:   Maxime Ripard <maxime@...no.tech>
To:     Jernej Skrabec <jernej.skrabec@...l.net>
Cc:     wens@...e.org, robh+dt@...nel.org, mark.rutland@....com,
        a.zummo@...ertech.it, alexandre.belloni@...tlin.com,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org
Subject: Re: [PATCH 1/2] rtc: sun6i: Make external 32k oscillator optional

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@...l.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?

Maxime

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