linux-kernel - Re: [PATCH V2] drivers/rtc/rtc-palmas.c: support for backup battery charging

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Date:	Thu, 1 Aug 2013 18:09:41 +0300
From:	Felipe Balbi <balbi@...com>
To:	Laxman Dewangan <ldewangan@...dia.com>
CC:	<akpm@...ux-foundation.org>, <grant.likely@...aro.org>,
	<rob.herring@...xeda.com>, <rob@...dley.net>,
	<devicetree@...r.kernel.org>, <linux-doc@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <rtc-linux@...glegroups.com>,
	<gg@...mlogic.co.uk>, <kishon@...com>, <swarren@...dia.com>,
	<pawel.moll@....com>, <Mark.Rutland@....com>,
	<ian.campbell@...rix.com>, <broonie@...nel.org>
Subject: Re: [PATCH V2] drivers/rtc/rtc-palmas.c: support for backup battery
 charging

Hi,

On Thu, Aug 01, 2013 at 08:01:11PM +0530, Laxman Dewangan wrote:
> Palmas series device like TPS65913, TPS80036 supports the backup battery
> for powering the RTC when no other energy source is available.
> 
> The backup battery is optional, connected to the VBACKUP pin, and can be
> nonrechargeable or rechargeable. The rechargeable battery can be charged
> from the system supply using the backup battery charger.
> 
> Add support for enabling charging of this backup battery.  Also add the DT
> binding document and the new properties to have this support.
> 
> Signed-off-by: Laxman Dewangan <ldewangan@...dia.com>
> ---
> Changes from V1:
> - Converted DT property to boolean.
> - cleanups as use "...".
> 
>  .../devicetree/bindings/rtc/rtc-palmas.txt         |   28 ++++++++++++++++
>  drivers/rtc/rtc-palmas.c                           |   35 ++++++++++++++++++++
>  2 files changed, 63 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/devicetree/bindings/rtc/rtc-palmas.txt
> 
> diff --git a/Documentation/devicetree/bindings/rtc/rtc-palmas.txt b/Documentation/devicetree/bindings/rtc/rtc-palmas.txt
> new file mode 100644
> index 0000000..c8c9def
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/rtc/rtc-palmas.txt
> @@ -0,0 +1,28 @@
> +Palmas RTC controller bindings
> +
> +Required properties:
> +- compatible:
> +  - "ti,palmas-rtc" for palma series of the RTC controller
> +- interrupt-parent: Parent interrupt device, must be handle of palmas node.
> +- interrupts: Interrupt number of RTC submodule on device.
> +
> +Optional properties:
> +- ti,back-battery-charge-enable: The palmas series device like TPS65913 or
> +	TPS80036 supports the battery backup for powering the RTC when main
> +	battery is removed or in very low power state. This flag will enable
> +	the backup battery charging.
> +- ti,back-charge-low-current: Configure lower charging current. Device supports the
> +	charging current as < 100mA or >100mA. Low current will set as <100mA.
> +
> +Example:
> +	palmas: tps65913@58 {
> +		...
> +		palmas_rtc: rtc {
> +			compatible = "ti,palmas-rtc";
> +			interrupt-parent = <&palmas>;
> +			interrupts = <8 0>;
> +			ti,back-battery-charge-enable;
> +			ti,back-charge-low-current;
> +		};
> +		...
> +	};
> diff --git a/drivers/rtc/rtc-palmas.c b/drivers/rtc/rtc-palmas.c
> index a1fecc8..7f34e33 100644
> --- a/drivers/rtc/rtc-palmas.c
> +++ b/drivers/rtc/rtc-palmas.c
> @@ -238,6 +238,15 @@ static int palmas_rtc_probe(struct platform_device *pdev)
>  	struct palmas *palmas = dev_get_drvdata(pdev->dev.parent);
>  	struct palmas_rtc *palmas_rtc = NULL;
>  	int ret;
> +	bool enable_bb_charging = false;
> +	bool low_bb_charging;
> +
> +	if (pdev->dev.of_node) {
> +		enable_bb_charging = of_property_read_bool(pdev->dev.of_node,
> +					"ti,back-battery-charge-enable");
> +		low_bb_charging = of_property_read_bool(pdev->dev.of_node,
> +					"ti,back-charge-low-current");
> +	}
>  
>  	palmas_rtc = devm_kzalloc(&pdev->dev, sizeof(struct palmas_rtc),
>  			GFP_KERNEL);
> @@ -254,6 +263,32 @@ static int palmas_rtc_probe(struct platform_device *pdev)
>  	palmas_rtc->dev = &pdev->dev;
>  	platform_set_drvdata(pdev, palmas_rtc);
>  
> +	if (enable_bb_charging) {
> +		unsigned reg = 0;
> +
> +		if (low_bb_charging)
> +			reg |= PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG;
> +
> +		ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
> +			PALMAS_BACKUP_BATTERY_CTRL,
> +			PALMAS_BACKUP_BATTERY_CTRL_BBS_BBC_LOW_ICHRG, reg);
> +		if (ret < 0) {
> +			dev_err(&pdev->dev,
> +				"BACKUP_BATTERY_CTRL update failed, %d\n", ret);
> +			return ret;
> +		}
> +
> +		ret = palmas_update_bits(palmas, PALMAS_PMU_CONTROL_BASE,
> +			PALMAS_BACKUP_BATTERY_CTRL,
> +			PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN,
> +			PALMAS_BACKUP_BATTERY_CTRL_BB_CHG_EN);
> +		if (ret < 0) {
> +			dev_err(&pdev->dev,
> +				"BACKUP_BATTERY_CTRL update failed, %d\n", ret);
> +			return ret;
> +		}

I wonder if this should be exposed via power_supply class, although it's
not really a power supply. So perhaps not needed :-s

looks good though (can't test as I don't have any boards available right
now):

Reviewed-by: Felipe Balbi <balbi@...com>

-- 
balbi

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