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Subject: Re: [PATCH] arm64: dts: meson: enable rtc node on Khadas VIM1/VIM2
 boards
To:     Christian Hewitt <christianshewitt@gmail.com>,
        Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Kevin Hilman <khilman@baylibre.com>,
        devicetree@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-amlogic@lists.infradead.org, linux-kernel@vger.kernel.org
Cc:     Artem Lapkin <art@khadas.com>
References: <20201116064147.12062-1-christianshewitt@gmail.com>
From:   Neil Armstrong <narmstrong@baylibre.com>
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Organization: Baylibre
Message-ID: <9e790744-c966-0ed6-349e-b1e0013f5193@baylibre.com>
Date:   Mon, 16 Nov 2020 09:36:07 +0100
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On 16/11/2020 07:41, Christian Hewitt wrote:
> Enable the rtc node on VIM1/VIM2 boards so users can simply attach a power
> cell and use the on-board RTC without modifying the device-tree.
> 
> Cold boot with no cell attached is gracefully handled:
> 
> VIM2:~ # dmesg | grep rtc
> [    7.716150] rtc-hym8563 1-0051: no valid clock/calendar values available
> [    7.716957] rtc-hym8563 1-0051: registered as rtc0
> [    7.729850] rtc-hym8563 1-0051: no valid clock/calendar values available
> [    7.729877] rtc-hym8563 1-0051: hctosys: unable to read the hardware clock
> [    8.126768] rtc-hym8563 1-0051: no valid clock/calendar values available
> 
> Warm boot (and any boot with cell attached) recalls stored values resulting
> in consistently faster (re)boot times:
> 
> VIM2:~ # dmesg | grep rtc
> [    7.441671] rtc-hym8563 1-0051: registered as rtc0
> [    7.442663] rtc-hym8563 1-0051: setting system clock to 2020-11-16T05:49:59 UTC (1605505799)
> 
> Suggested-by: Artem Lapkin <art@khadas.com>
> Signed-off-by: Christian Hewitt <christianshewitt@gmail.com>
> ---
> 
> This supersedes other recent attempts by Art to make the same change [0]
> and [1] which were rejected for lack of justification for the change and
> leaving comments behind. I have been using the same changes in my own
> tree for a while.
> 
> Christian
> 
> [0] https://patchwork.kernel.org/project/linux-amlogic/patch/20200925033017.1790973-8-art@khadas.com/
> [1] https://patchwork.kernel.org/project/linux-amlogic/patch/20200925033017.1790973-9-art@khadas.com/
> 
>  arch/arm64/boot/dts/amlogic/meson-gxl-s905x-khadas-vim.dts | 3 +--
>  arch/arm64/boot/dts/amlogic/meson-gxm-khadas-vim2.dts      | 3 +--
>  2 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-khadas-vim.dts b/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-khadas-vim.dts
> index 8bcdffdf55d0..638a5992d760 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-khadas-vim.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-gxl-s905x-khadas-vim.dts
> @@ -97,8 +97,7 @@
>  	pinctrl-names = "default";
>  
>  	rtc: rtc@51 {
> -		/* has to be enabled manually when a battery is connected: */
> -		status = "disabled";
> +		status = "okay";
>  		compatible = "haoyu,hym8563";
>  		reg = <0x51>;
>  		#clock-cells = <0>;
> diff --git a/arch/arm64/boot/dts/amlogic/meson-gxm-khadas-vim2.dts b/arch/arm64/boot/dts/amlogic/meson-gxm-khadas-vim2.dts
> index bff8ec2c1c70..da000c10b945 100644
> --- a/arch/arm64/boot/dts/amlogic/meson-gxm-khadas-vim2.dts
> +++ b/arch/arm64/boot/dts/amlogic/meson-gxm-khadas-vim2.dts
> @@ -228,8 +228,7 @@
>  	pinctrl-names = "default";
>  
>  	rtc: rtc@51 {
> -		/* has to be enabled manually when a battery is connected: */
> -		status = "disabled";
> +		status = "okay";
>  		compatible = "haoyu,hym8563";
>  		reg = <0x51>;
>  		#clock-cells = <0>;
> 

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>