linux-kernel - Re: [PATCH 06/33] ARM: dts: exynos: Correct S3C RTC bindings and enable it in Universal C210

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Date:   Mon, 31 Aug 2020 11:49:38 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     Krzysztof Kozlowski <krzk@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Kukjin Kim <kgene@...nel.org>, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-samsung-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Denis GNUtoo Carikli <GNUtoo@...erdimension.org>,
        Simon Shields <simon@...eageos.org>
Cc:     Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Sylwester Nawrocki <snawrocki@...nel.org>
Subject: Re: [PATCH 06/33] ARM: dts: exynos: Correct S3C RTC bindings and
 enable it in Universal C210


On 30.08.2020 15:51, Krzysztof Kozlowski wrote:
> The S3C RTC requires 32768 Hz clock as input which is provided by PMIC.
> However there is no clock provided for the PMIC and the driver registers
> the clock as regulator.  This is an old driver which will not be updated
> so add a workaround - add a fixed-clock to fill missing clock phandle
> reference in S3C RTC.  The "clock" regulator in PMIC is already present
> and enabled.
>
> This allows to enable the S3C RTC and fixes dtbs_check warnings:
>
>    arch/arm/boot/dts/exynos4210-universal_c210.dt.yaml: rtc@...70000: clocks: [[5, 346]] is too short
>    arch/arm/boot/dts/exynos4210-universal_c210.dt.yaml: rtc@...70000: clock-names: ['rtc'] is too short
>
> Signed-off-by: Krzysztof Kozlowski <krzk@...nel.org>

Confirmed, this workaround enables s3c-rtc driver operation on this board.

Tested-by: Marek Szyprowski <m.szyprowski@...sung.com>

> ---
>   arch/arm/boot/dts/exynos4210-universal_c210.dts | 13 +++++++++++++
>   1 file changed, 13 insertions(+)
>
> diff --git a/arch/arm/boot/dts/exynos4210-universal_c210.dts b/arch/arm/boot/dts/exynos4210-universal_c210.dts
> index 99ce53b120ac..9479e41bdc2a 100644
> --- a/arch/arm/boot/dts/exynos4210-universal_c210.dts
> +++ b/arch/arm/boot/dts/exynos4210-universal_c210.dts
> @@ -39,6 +39,13 @@
>   			compatible = "samsung,clock-xusbxti";
>   			clock-frequency = <24000000>;
>   		};
> +
> +		pmic_ap_clk: pmic-ap-clk {
> +			/* Workaround for missing clock on PMIC */
> +			compatible = "fixed-clock";
> +			#clock-cells = <0>;
> +			clock-frequency = <32768>;
> +		};
>   	};
>   
>   	vemmc_reg: voltage-regulator {
> @@ -537,6 +544,12 @@
>   	status = "okay";
>   };
>   
> +&rtc {
> +	status = "okay";
> +	clocks = <&clock CLK_RTC>, <&pmic_ap_clk>;
> +	clock-names = "rtc", "rtc_src";
> +};
> +
>   &sdhci_0 {
>   	bus-width = <8>;
>   	non-removable;

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland