linux-kernel - Re: [PATCH v2 1/4] iio: adc: rockchip_saradc: reset saradc controller before programming it

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Message-ID: <57976814.3040605@roeck-us.net>
Date:	Tue, 26 Jul 2016 06:39:32 -0700
From:	Guenter Roeck <linux@...ck-us.net>
To:	Caesar Wang <wxt@...k-chips.com>, jic23@...nel.org, heiko@...ech.de
Cc:	devicetree@...r.kernel.org, linux-rockchip@...ts.infradead.org,
	linux-arm-kernel@...ts.infradead.org, robh+dt@...nel.org,
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
	john@...anate.com, dianders@...omium.org
Subject: Re: [PATCH v2 1/4] iio: adc: rockchip_saradc: reset saradc controller
 before programming it

On 07/26/2016 05:13 AM, Caesar Wang wrote:
> SARADC controller needs to be reset before programming it, otherwise
> it will not function properly.
>
> Signed-off-by: Caesar Wang <wxt@...k-chips.com>
> Cc: Jonathan Cameron <jic23@...nel.org>
> Cc: Heiko Stuebner <heiko@...ech.de>
> Cc: Rob Herring <robh+dt@...nel.org>
> Cc: linux-iio@...r.kernel.org
> Cc: linux-rockchip@...ts.infradead.org
>
> ---
>
> Changes in v2:
> - Make the reset as an optional property, since it should work
> with old devicetrees as well.
>
>   .../bindings/iio/adc/rockchip-saradc.txt           |  7 +++++
>   drivers/iio/adc/Kconfig                            |  1 +
>   drivers/iio/adc/rockchip_saradc.c                  | 31 ++++++++++++++++++++++
>   3 files changed, 39 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/iio/adc/rockchip-saradc.txt b/Documentation/devicetree/bindings/iio/adc/rockchip-saradc.txt
> index bf99e2f..205593f 100644
> --- a/Documentation/devicetree/bindings/iio/adc/rockchip-saradc.txt
> +++ b/Documentation/devicetree/bindings/iio/adc/rockchip-saradc.txt
> @@ -16,6 +16,11 @@ Required properties:
>   - vref-supply: The regulator supply ADC reference voltage.
>   - #io-channel-cells: Should be 1, see ../iio-bindings.txt
>
> +Optional properties:
> +- resets: Must contain an entry for each entry in reset-names if need support
> +	  this option. See ../reset/reset.txt for details.
> +- reset-names: Must include the name "saradc-apb".
> +
>   Example:
>   	saradc: saradc@...6c000 {
>   		compatible = "rockchip,saradc";
> @@ -23,6 +28,8 @@ Example:
>   		interrupts = <GIC_SPI 26 IRQ_TYPE_LEVEL_HIGH>;
>   		clocks = <&cru SCLK_SARADC>, <&cru PCLK_SARADC>;
>   		clock-names = "saradc", "apb_pclk";
> +		resets = <&cru SRST_SARADC>;
> +		reset-names = "saradc-apb";
>   		#io-channel-cells = <1>;
>   		vref-supply = <&vcc18>;
>   	};
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 1de31bd..7675772 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -389,6 +389,7 @@ config QCOM_SPMI_VADC
>   config ROCKCHIP_SARADC
>   	tristate "Rockchip SARADC driver"
>   	depends on ARCH_ROCKCHIP || (ARM && COMPILE_TEST)
> +	depends on RESET_CONTROLLER
>   	help
>   	  Say yes here to build support for the SARADC found in SoCs from
>   	  Rockchip.
> diff --git a/drivers/iio/adc/rockchip_saradc.c b/drivers/iio/adc/rockchip_saradc.c
> index f9ad6c2..dc1379f 100644
> --- a/drivers/iio/adc/rockchip_saradc.c
> +++ b/drivers/iio/adc/rockchip_saradc.c
> @@ -21,6 +21,8 @@
>   #include <linux/of_device.h>
>   #include <linux/clk.h>
>   #include <linux/completion.h>
> +#include <linux/delay.h>
> +#include <linux/reset.h>
>   #include <linux/regulator/consumer.h>
>   #include <linux/iio/iio.h>
>
> @@ -53,6 +55,7 @@ struct rockchip_saradc {
>   	struct clk		*clk;
>   	struct completion	completion;
>   	struct regulator	*vref;
> +	struct reset_control	*reset;
>   	const struct rockchip_saradc_data *data;
>   	u16			last_val;
>   };
> @@ -190,6 +193,16 @@ static const struct of_device_id rockchip_saradc_match[] = {
>   };
>   MODULE_DEVICE_TABLE(of, rockchip_saradc_match);
>
> +/**
> + * Reset SARADC Controller.
> + */
> +static void rockchip_saradc_reset_controller(struct reset_control *reset)
> +{
> +	reset_control_assert(reset);
> +	usleep_range(10, 20);
> +	reset_control_deassert(reset);
> +}
> +
>   static int rockchip_saradc_probe(struct platform_device *pdev)
>   {
>   	struct rockchip_saradc *info = NULL;
> @@ -218,6 +231,21 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
>   	if (IS_ERR(info->regs))
>   		return PTR_ERR(info->regs);
>
> +	/*
> +	 * The reset should be an optional property, as it should work
> +	 * with old devicetrees as well
> +	 */
> +	info->reset = devm_reset_control_get_optional(&pdev->dev,
> +			"saradc-apb");

Does anyone know what the _optional API is for ? It seems to be exactly the same
as devm_reset_control_get().

Guenter

> +	if (IS_ERR(info->reset)) {
> +		ret = PTR_ERR(info->reset);
> +		if (ret != -ENOENT)
> +			return ret;
> +
> +		dev_dbg(&pdev->dev, "no reset control found\n");
> +		info->reset = NULL;
> +	}
> +
>   	init_completion(&info->completion);
>
>   	irq = platform_get_irq(pdev, 0);
> @@ -252,6 +280,9 @@ static int rockchip_saradc_probe(struct platform_device *pdev)
>   		return PTR_ERR(info->vref);
>   	}
>
> +	if (info->reset)
> +		rockchip_saradc_reset_controller(info->reset);
> +
>   	/*
>   	 * Use a default value for the converter clock.
>   	 * This may become user-configurable in the future.
>