Re: [PATCH V4] iio: adc: Add Renesas GyroADC driver

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On 10/01/17 21:33, Marek Vasut wrote:
> Add IIO driver for the Renesas RCar GyroADC block. This block is a
> simple 4/8-channel ADC which samples 12/15/24 bits of data every
> cycle from all channels.
> 
> Signed-off-by: Marek Vasut <marek.vasut@xxxxxxxxx>
> Cc: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
> Cc: Simon Horman <horms+renesas@xxxxxxxxxxxx>
Various minor bits and pieces.  In particular I'm not keen on carrying
on probing once we have a device tree entry that is 'wrong'.  I'd bail there
and then.  This should never happen an is a bug.

The only obvious exception would be if the device name wasn't supported 'yet'.
Things to do with how it is described should result in hard errors.

Anyhow, basically looks pretty good.

Jonathan
> ---
> V2: - Spelling fixes
>     - Rename the driver source file to rcar-gyroadc
>     - Rework the channel sample width handling
>     - Use iio_device_claim_mode_direct()
>     - Rename "renesas,rcar-gyroadc" to "renesas,r8a7791-gyroadc" and
>       rename "renesas,rcar-gyroadc-r8a7792" to "renesas,r8a7792-gyroadc"
>       to match the new naming scheme (WARNING: scif uses the old one!)
>     - Switch to using regulators for channel voltage reference, add new
>       properties renesas,gyroadc-vref-chN-supply for N in 0..7
>     - Handle vref regulators as optional to, make channels without
>       vref regulator return EINVAL on read.
>     - Fix module license to GPL
>     - Drop interrupt.h include
>     - Rename clk to iclk
>     - Rename RCar to R-Car
>     - Rework the invalid mode handling
>     - Don't print error message on EPROBE_DEFER
>     - Drop fclk handling, use runtime PM for that instead
> V3: - More R-Car spelling fixes
>     - Flip checks for V2H, since that's the only one that has
>       interrupt registers
>     - Replace if-else statement with switch statement in init_mode
>     - Use unsigned types where applicable
>     - Rework timing calculation slightly to drop if-else block
>     - Use DIV_ROUND_CLOSEST
> V4: - Add renesas,rcar-gyroadc fallback compatible string into the bindings
>     - Rework the ADC bindings to use per-channel subdevs
>     - Support more compatible ADC chips
> ---
>  .../bindings/iio/adc/renesas,gyroadc.txt           |  70 +++
>  MAINTAINERS                                        |   6 +
>  drivers/iio/adc/Kconfig                            |  10 +
>  drivers/iio/adc/Makefile                           |   1 +
>  drivers/iio/adc/rcar-gyroadc.c                     | 531 +++++++++++++++++++++
>  5 files changed, 618 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/renesas,gyroadc.txt
>  create mode 100644 drivers/iio/adc/rcar-gyroadc.c
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/renesas,gyroadc.txt b/Documentation/devicetree/bindings/iio/adc/renesas,gyroadc.txt
> new file mode 100644
> index 000000000000..2dcea9c8895b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/renesas,gyroadc.txt
> @@ -0,0 +1,70 @@
> +* Renesas RCar GyroADC device driver
> +
> +Required properties:
> +- compatible:	Should be "renesas,<chip>-gyroadc", "renesas,rcar-gyroadc".
> +		Use "renesas,r8a7792-gyroadc" for a GyroADC with interrupt
> +		block found in R8A7792.
> +- reg:		Address and length of the register set for the device
> +- clocks:	References to all the clocks specified in the clock-names
> +		property as specified in
> +		Documentation/devicetree/bindings/clock/clock-bindings.txt.
> +- clock-names:	Shall contain "fck" and "if". The "fck" is the GyroADC block
> +		clock, the "if" is the interface clock.
> +- power-domains: Must contain a reference to the PM domain, if available.
> +- #address-cells: Should be <1> (setting for the subnodes)
> +- #size-cells:	Should be <0> (setting for the subnodes)
> +
> +Sub-nodes:
> +Optionally you can define subnodes which define the reference voltage
> +for the analog inputs.
> +
> +Required properties for subnodes:
> +- compatible:	Should be either of:
> +		"fujitsu,mb88101a"
> +			- Fujitsu MB88101A compatible mode,
> +			  12bit sampling, 4 channels
> +		"ti,adcs7476" or "ti,adc121" or "adi,ad7476"
> +			- TI ADCS7476 / TI ADC121 / ADI AD7476 compatible mode,
> +			  15bit sampling, 8 channels
> +		"maxim,max1162" or "maxim,max11100"
> +			- Maxim MAX1162 / Maxim MAX11100 compatible mode,
> +			  16bit sampling, 8 channels
Worth putting something here about how this might be interfaced.
Realistically we are either looking at some extra circuitry or supporting
only 3 of the channels.
The max11100 is only a single channel device for example. This description
doesn't make it clear that 8 of them would be needed to do 8 channels.
> +- reg:		Should be the number of the analog input.
> +- vref-supply:	Reference to the channel reference voltage regulator.
> +
> +Example:
> +	vref_max1162: regulator-vref-max1162 {
> +		compatible = "regulator-fixed";
> +
> +		regulator-name = "MAX1162 Vref";
> +		regulator-min-microvolt = <4096000>;
> +		regulator-max-microvolt = <4096000>;
> +	};
> +
> +	&adc {
> +		compatible = "renesas,r8a7791-gyroadc", "renesas,rcar-gyroadc";
> +		reg = <0 0xe6e54000 0 64>;
> +		clocks = <&mstp9_clks R8A7791_CLK_GYROADC>, <&clk_65m>;
> +		clock-names = "fck", "if";
> +		power-domains = <&sysc R8A7791_PD_ALWAYS_ON>;
> +
> +		pinctrl-0 = <&adc_pins>;
> +		pinctrl-names = "default";
> +
> +		status = "okay";
> +
> +		#address-cells = <1>;
> +		#size-cells = <0>;
> +
> +		adc@0 {
> +			reg = <0>;
> +			compatible = "maxim,max1162";
> +			vref-supply = <&vref_max1162>;
> +		};
> +
> +		adc@1 {
> +			reg = <1>;
> +			compatible = "maxim,max1162";
> +			vref-supply = <&vref_max1162>;
> +		};
> +	};
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 890fc9e3c191..498e8a755eb6 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -10276,6 +10276,12 @@ L:	linux-renesas-soc@xxxxxxxxxxxxxxx
>  F:	drivers/net/ethernet/renesas/
>  F:	include/linux/sh_eth.h
>  
> +RENESAS R-CAR GYROADC DRIVER
> +M:	Marek Vasut <marek.vasut@xxxxxxxxx>
> +L:	linux-iio@xxxxxxxxxxxxxxx
> +S:	Supported
> +F:	drivers/iio/adc/rcar_gyro_adc.c
> +
>  RENESAS USB2 PHY DRIVER
>  M:	Yoshihiro Shimoda <yoshihiro.shimoda.uh@xxxxxxxxxxx>
>  L:	linux-renesas-soc@xxxxxxxxxxxxxxx
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 99c051490eff..f9954c71048d 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -408,6 +408,16 @@ config QCOM_SPMI_VADC
>  	  To compile this driver as a module, choose M here: the module will
>  	  be called qcom-spmi-vadc.
>  
> +config RCAR_GYRO_ADC
> +	tristate "Renesas R-Car GyroADC driver"
> +	depends on ARCH_RCAR_GEN2 || (ARM && COMPILE_TEST)
> +	help
> +	  Say yes here to build support for the GyroADC found in Renesas
> +	  R-Car Gen2 SoCs.
Put a bit more detail here perhaps - it's not really an ADC afterall but
a rather dumb spi offload engine. If it was slightly smarter I'd suggest
supporting it through that infrastructure.  That would require changes
in every relevant driver though so not terribly elegant.
> +
> +	  To compile this driver as a module, choose M here: the
> +	  module will be called rcar-gyroadc.
> +
>  config ROCKCHIP_SARADC
>  	tristate "Rockchip SARADC driver"
>  	depends on ARCH_ROCKCHIP || (ARM && COMPILE_TEST)
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index 7a40c04c311f..13db7c2bffc8 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -39,6 +39,7 @@ obj-$(CONFIG_NAU7802) += nau7802.o
>  obj-$(CONFIG_PALMAS_GPADC) += palmas_gpadc.o
>  obj-$(CONFIG_QCOM_SPMI_IADC) += qcom-spmi-iadc.o
>  obj-$(CONFIG_QCOM_SPMI_VADC) += qcom-spmi-vadc.o
> +obj-$(CONFIG_RCAR_GYRO_ADC) += rcar-gyroadc.o
>  obj-$(CONFIG_ROCKCHIP_SARADC) += rockchip_saradc.o
>  obj-$(CONFIG_STX104) += stx104.o
>  obj-$(CONFIG_TI_ADC081C) += ti-adc081c.o
> diff --git a/drivers/iio/adc/rcar-gyroadc.c b/drivers/iio/adc/rcar-gyroadc.c
> new file mode 100644
> index 000000000000..14f139613e1c
> --- /dev/null
> +++ b/drivers/iio/adc/rcar-gyroadc.c
> @@ -0,0 +1,531 @@
> +/*
> + * Renesas R-Car GyroADC driver
> + *
> + * Copyright 2016 Marek Vasut <marek.vasut@xxxxxxxxx>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/platform_device.h>
> +#include <linux/delay.h>
> +#include <linux/kernel.h>
> +#include <linux/slab.h>
> +#include <linux/io.h>
> +#include <linux/clk.h>
> +#include <linux/of.h>
> +#include <linux/of_irq.h>
> +#include <linux/regulator/consumer.h>
> +#include <linux/of_platform.h>
> +#include <linux/err.h>
> +#include <linux/pm_runtime.h>
> +
> +#include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/sysfs.h>
> +#include <linux/iio/trigger.h>
> +
> +/* GyroADC registers. */
> +#define RCAR_GYROADC_MODE_SELECT		0x00
> +#define RCAR_GYROADC_MODE_SELECT_1_MB88101A	0x0
> +#define RCAR_GYROADC_MODE_SELECT_2_ADCS7476	0x1
> +#define RCAR_GYROADC_MODE_SELECT_3_MAX1162	0x3
> +
> +#define RCAR_GYROADC_START_STOP			0x04
> +#define RCAR_GYROADC_START_STOP_START		BIT(0)
> +
> +#define RCAR_GYROADC_CLOCK_LENGTH		0x08
> +#define RCAR_GYROADC_1_25MS_LENGTH		0x0c
> +
> +#define RCAR_GYROADC_REALTIME_DATA(ch)		(0x10 + ((ch) * 4))
> +#define RCAR_GYROADC_100MS_ADDED_DATA(ch)	(0x30 + ((ch) * 4))
> +#define RCAR_GYROADC_10MS_AVG_DATA(ch)		(0x50 + ((ch) * 4))
> +
> +#define RCAR_GYROADC_FIFO_STATUS		0x70
> +#define RCAR_GYROADC_FIFO_STATUS_EMPTY(ch)	BIT(0 + (4 * (ch)))
> +#define RCAR_GYROADC_FIFO_STATUS_FULL(ch)	BIT(1 + (4 * (ch)))
> +#define RCAR_GYROADC_FIFO_STATUS_ERROR(ch)	BIT(2 + (4 * (ch)))
> +
> +#define RCAR_GYROADC_INTR			0x74
> +#define RCAR_GYROADC_INTR_INT			BIT(0)
> +
> +#define RCAR_GYROADC_INTENR			0x78
> +#define RCAR_GYROADC_INTENR_INTEN		BIT(0)
> +
> +#define RCAR_GYROADC_SAMPLE_RATE		800	/* Hz */
> +
> +enum rcar_gyroadc_model {
> +	RCAR_GYROADC_MODEL_DEFAULT,
> +	RCAR_GYROADC_MODEL_R8A7792,
> +};
> +
> +struct rcar_gyroadc {
> +	struct device			*dev;
> +	void __iomem			*regs;
> +	struct clk			*iclk;
> +	struct regulator		*vref[8];
> +	unsigned int			num_channels;
> +	enum rcar_gyroadc_model		model;
> +	unsigned int			mode;
> +	unsigned int			sample_width;
> +	u32				buffer[8];
> +};
> +
> +static void rcar_gyroadc_hw_init(struct rcar_gyroadc *priv)
> +{
> +	const unsigned long clk_mhz = clk_get_rate(priv->iclk) / 1000000;
> +	const unsigned long clk_mul =
> +		(priv->mode == RCAR_GYROADC_MODE_SELECT_1_MB88101A) ? 10 : 5;
> +
> +	/* Stop the GyroADC. */
> +	writel(0, priv->regs + RCAR_GYROADC_START_STOP);
> +
> +	/* Disable IRQ on V2H. */
> +	if (priv->model == RCAR_GYROADC_MODEL_R8A7792)
> +		writel(0, priv->regs + RCAR_GYROADC_INTENR);
> +
> +	/* Set mode and timing. */
> +	writel(priv->mode, priv->regs + RCAR_GYROADC_MODE_SELECT);
> +	writel(clk_mhz * clk_mul, priv->regs + RCAR_GYROADC_CLOCK_LENGTH);
> +	writel(clk_mhz * 1250, priv->regs + RCAR_GYROADC_1_25MS_LENGTH);
> +
> +	/*
> +	 * We can possibly turn the sampling on/off on-demand to reduce power
> +	 * consumption, but for the sake of quick availability of samples, we
> +	 * don't do it now.
Typically, if you want to do this, do it with runtime_pm and use the
auto suspend stuff.  Can work well.
> +	 */
> +	writel(RCAR_GYROADC_START_STOP_START,
> +	       priv->regs + RCAR_GYROADC_START_STOP);
> +
> +	/* Wait for the first conversion to complete. */
> +	udelay(1250);
> +}
> +
> +#define RCAR_GYROADC_CHAN(_idx) {				\
> +	.type			= IIO_VOLTAGE,			\
> +	.indexed		= 1,				\
> +	.channel		= (_idx),			\
> +	.info_mask_separate	= BIT(IIO_CHAN_INFO_RAW) |	\
> +				  BIT(IIO_CHAN_INFO_SCALE),	\
> +	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ), \
> +}
> +
> +static const struct iio_chan_spec rcar_gyroadc_iio_channels_1[] = {
> +	RCAR_GYROADC_CHAN(0),
> +	RCAR_GYROADC_CHAN(1),
> +	RCAR_GYROADC_CHAN(2),
> +	RCAR_GYROADC_CHAN(3),
> +};
> +
> +static const struct iio_chan_spec rcar_gyroadc_iio_channels_2[] = {
> +	RCAR_GYROADC_CHAN(0),
> +	RCAR_GYROADC_CHAN(1),
> +	RCAR_GYROADC_CHAN(2),
> +	RCAR_GYROADC_CHAN(3),
> +	RCAR_GYROADC_CHAN(4),
> +	RCAR_GYROADC_CHAN(5),
> +	RCAR_GYROADC_CHAN(6),
> +	RCAR_GYROADC_CHAN(7),
> +};
> +
> +/*
> + * NOTE: The data we receive in mode 3 from MAX1162 have MSByte = 0,
> + *       therefore we only use 16bit realbits here instead of 24.
Umm. That would be a fair comment if realbits was set at all!
With what you are currently supporting it shouldn't be.
> + */
> +static const struct iio_chan_spec rcar_gyroadc_iio_channels_3[] = {
> +	RCAR_GYROADC_CHAN(0),
> +	RCAR_GYROADC_CHAN(1),
> +	RCAR_GYROADC_CHAN(2),
> +	RCAR_GYROADC_CHAN(3),
> +	RCAR_GYROADC_CHAN(4),
> +	RCAR_GYROADC_CHAN(5),
> +	RCAR_GYROADC_CHAN(6),
> +	RCAR_GYROADC_CHAN(7),
> +};
> +
> +static int rcar_gyroadc_read_raw(struct iio_dev *indio_dev,
> +				 struct iio_chan_spec const *chan,
> +				 int *val, int *val2, long mask)
> +{
> +	struct rcar_gyroadc *priv = iio_priv(indio_dev);
> +	struct regulator *consumer = priv->vref[chan->channel];
> +	unsigned int datareg = RCAR_GYROADC_REALTIME_DATA(chan->channel);
> +	unsigned int vref;
> +	int ret;
> +
> +	switch (mask) {
> +	case IIO_CHAN_INFO_RAW:
> +		if (chan->type != IIO_VOLTAGE)
> +			return -EINVAL;
> +
> +		/* Channel not connected. */
> +		if (!consumer)
> +			return -EINVAL;
> +
> +		ret = iio_device_claim_direct_mode(indio_dev);
> +		if (ret)
> +			return ret;
> +
> +		*val = readl(priv->regs + datareg);
> +		*val &= BIT(priv->sample_width) - 1;
> +
> +		iio_device_release_direct_mode(indio_dev);
> +
> +		return IIO_VAL_INT;
> +	case IIO_CHAN_INFO_SCALE:
> +		/* Channel not connected. */
> +		if (!consumer)
> +			return -EINVAL;
> +
> +		vref = regulator_get_voltage(consumer);
> +		*val = 0;
> +		*val2 = DIV_ROUND_CLOSEST(vref * 1000, 0x10000);
spacing is a bit variable.  Sometimes you leave a line before the return,
sometimes you don't. Pick one or the other and it'll read slightly better!
> +		return IIO_VAL_INT_PLUS_NANO;
> +	case IIO_CHAN_INFO_SAMP_FREQ:
> +		*val = RCAR_GYROADC_SAMPLE_RATE;
> +		return IIO_VAL_INT;
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +static int rcar_gyroadc_reg_access(struct iio_dev *indio_dev,
> +				   unsigned int reg, unsigned int writeval,
> +				   unsigned int *readval)
> +{
> +	struct rcar_gyroadc *priv = iio_priv(indio_dev);
> +	unsigned int maxreg = RCAR_GYROADC_FIFO_STATUS;
> +
> +	if (readval == NULL)
> +		return -EINVAL;
> +
> +	if (reg % 4)
> +		return -EINVAL;
> +
> +	/* Handle the V2H case with extra interrupt block. */
> +	if (priv->model == RCAR_GYROADC_MODEL_R8A7792)
> +		maxreg = RCAR_GYROADC_INTENR;
> +
> +	if (reg > maxreg)
> +		return -EINVAL;
> +
> +	*readval = readl(priv->regs + reg);
> +
> +	return 0;
> +}
> +
> +static const struct iio_info rcar_gyroadc_iio_info = {
> +	.driver_module		= THIS_MODULE,
> +	.read_raw		= rcar_gyroadc_read_raw,
> +	.debugfs_reg_access	= rcar_gyroadc_reg_access,
> +};
> +
> +static const struct of_device_id rcar_gyroadc_match[] = {
> +	{
> +		/* R-Car compatible GyroADC */
> +		.compatible	= "renesas,rcar-gyroadc",
> +		.data		= (void *)RCAR_GYROADC_MODEL_DEFAULT,
> +	}, {
> +		/* R-Car V2H specialty with interrupt registers. */
> +		.compatible	= "renesas,r8a7792-gyroadc",
> +		.data		= (void *)RCAR_GYROADC_MODEL_R8A7792,
> +	}, {
> +		/* sentinel */
> +	}
> +};
> +
> +MODULE_DEVICE_TABLE(of, rcar_gyroadc_match);
> +
> +static const struct of_device_id rcar_gyroadc_child_match[] = {
> +	/* Mode 1 ADCs */
> +	{
> +		.compatible	= "fujitsu,mb88101a",
> +		.data		= (void *)RCAR_GYROADC_MODE_SELECT_1_MB88101A,
> +	},
> +	/* Mode 2 ADCs */
> +	{
> +		.compatible	= "ti,adcs7476",
> +		.data		= (void *)RCAR_GYROADC_MODE_SELECT_2_ADCS7476,
> +	}, {
> +		.compatible	= "ti,adc121",
> +		.data		= (void *)RCAR_GYROADC_MODE_SELECT_2_ADCS7476,
> +	}, {
> +		.compatible	= "adi,ad7476",
> +		.data		= (void *)RCAR_GYROADC_MODE_SELECT_2_ADCS7476,
> +	},
> +	/* Mode 3 ADCs */
> +	{
> +		.compatible	= "maxim,max1162",
> +		.data		= (void *)RCAR_GYROADC_MODE_SELECT_3_MAX1162,
> +	}, {
> +		.compatible	= "maxim,max11100",
> +		.data		= (void *)RCAR_GYROADC_MODE_SELECT_3_MAX1162,
> +	},
> +	{ /* sentinel */ }
> +};
> +
> +static int rcar_gyroadc_parse_subdevs(struct iio_dev *indio_dev)
> +{
> +	const struct of_device_id *of_id;
> +	const struct iio_chan_spec *channels;
> +	struct rcar_gyroadc *priv = iio_priv(indio_dev);
> +	struct device *dev = priv->dev;
> +	struct device_node *np = dev->of_node;
> +	struct device_node *child;
> +	struct regulator *vref;
> +	unsigned int reg, maxreg;
> +	unsigned int adcmode, childmode;
> +	unsigned int sample_width;
> +	unsigned int num_channels;
> +	int ret, first = 1;
> +
> +	for_each_child_of_node(np, child) {
> +		of_id = of_match_node(rcar_gyroadc_child_match, child);
> +		if (!of_id) {
> +			dev_err(dev, "Ignoring unsupported ADC \"%s\".",
> +				child->name);
This is the only case that should result in a continue.
> +			continue;
> +		}
> +
> +		ret = of_property_read_u32(child, "reg", &reg);
> +		if (ret) {
> +			dev_err(dev,
> +				"Failed to get child reg property of ADC \"%s\".\n",
> +				child->name);
> +			continue;
> +		}
> +
> +		childmode = (unsigned int)of_id->data;
> +		switch (childmode) {
> +		case RCAR_GYROADC_MODE_SELECT_1_MB88101A:
> +			maxreg = 4;
> +			sample_width = 12;
> +			channels = rcar_gyroadc_iio_channels_1;
> +			num_channels = ARRAY_SIZE(rcar_gyroadc_iio_channels_1);
> +			break;
> +		case RCAR_GYROADC_MODE_SELECT_2_ADCS7476:
> +			maxreg = 8;
> +			sample_width = 15;
> +			channels = rcar_gyroadc_iio_channels_2;
> +			num_channels = ARRAY_SIZE(rcar_gyroadc_iio_channels_2);
> +			break;
> +		case RCAR_GYROADC_MODE_SELECT_3_MAX1162:
> +			maxreg = 8;
> +			sample_width = 16;
> +			channels = rcar_gyroadc_iio_channels_3;
> +			num_channels = ARRAY_SIZE(rcar_gyroadc_iio_channels_3);
> +			break;
> +		}
> +
> +		/* Channel number is too high. */
> +		if (reg >= maxreg) {
> +			dev_err(dev,
> +				"Only %i channels supported with %s, but reg = <%i>, ignoring.\n",
> +				maxreg, child->name, reg);
> +			continue;
> +		}
> +
> +		/* Child node selected different mode than the rest. */
> +		if (!first && (adcmode != childmode)) {
> +			dev_err(dev,
> +				"Channel %i uses different ADC mode than the rest, ignoring.\n",
> +				reg);
> +			continue;
Fail hard - not softly - I'd expect the probe to completely fail if the
device tree is invalid in this way.

Same is true for other conditions above. Don't paper over the issue please.
> +		}
> +
> +		/* Channel is valid, grab the regulator. */
> +		dev->of_node = child;
> +		vref = devm_regulator_get_optional(dev, "vref");
> +		dev->of_node = np;
> +		if (IS_ERR(vref)) {
> +			/*
> +			 * Regulator is not present, which means the channel
> +			 * supply is not connected.
> +			 */
> +			dev_dbg(dev, "Channel %i 'vref' supply not connected\n",
> +				reg);
Error out rather than carrying on to try other channels. If the device tree
is invalid we want to know and fail hard.
> +			continue;
> +		}
> +
> +		priv->vref[reg] = vref;
> +
> +		if (!first)
> +			continue;
> +
> +		/* First child node which passed sanity tests. */
> +		adcmode = childmode;
> +		first = 0;
> +
> +		priv->num_channels = maxreg;
> +		priv->mode = childmode;
> +		priv->sample_width = sample_width;
> +
> +		indio_dev->channels = channels;
> +		indio_dev->num_channels = num_channels;
> +	}
> +
> +	if (first) {
> +		dev_err(dev, "No valid ADC channels found, aborting.\n");
> +		return -EINVAL;
> +	}
> +
> +	return 0;
> +}
> +
> +static void rcar_gyroadc_deinit_supplies(struct iio_dev *indio_dev)
> +{
> +	struct rcar_gyroadc *priv = iio_priv(indio_dev);
> +	unsigned int i;
> +
> +	for (i = 0; i < priv->num_channels; i++) {
> +		if (!priv->vref[i])
> +			continue;
> +
> +		regulator_disable(priv->vref[i]);
> +	}
> +}
> +
> +static int rcar_gyroadc_init_supplies(struct iio_dev *indio_dev)
> +{
> +	struct rcar_gyroadc *priv = iio_priv(indio_dev);
> +	struct device *dev = priv->dev;
> +	unsigned int i;
> +	int ret;
> +
> +	for (i = 0; i < priv->num_channels; i++) {
> +		if (!priv->vref[i])
> +			continue;
> +
> +		ret = regulator_enable(priv->vref[i]);
> +		if (ret) {
> +			dev_err(dev, "Failed to enable regulator %i (ret=%i)\n",
> +				i, ret);
> +			goto err;
> +		}
> +	}
> +
> +	return 0;
> +
> +err:
> +	rcar_gyroadc_deinit_supplies(indio_dev);
> +	return ret;
> +}
> +
> +static int rcar_gyroadc_probe(struct platform_device *pdev)
> +{
> +	const struct of_device_id *of_id =
> +		of_match_device(rcar_gyroadc_match, &pdev->dev);
> +	struct device *dev = &pdev->dev;
> +	struct rcar_gyroadc *priv;
> +	struct iio_dev *indio_dev;
> +	struct resource *mem;
> +	int ret;
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
> +	if (!indio_dev) {
> +		dev_err(dev, "Failed to allocate IIO device.\n");
> +		return -ENOMEM;
> +	}
> +
> +	priv = iio_priv(indio_dev);
> +	priv->dev = dev;
> +
> +	mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	priv->regs = devm_ioremap_resource(dev, mem);
> +	if (IS_ERR(priv->regs))
> +		return PTR_ERR(priv->regs);
> +
> +	priv->iclk = devm_clk_get(dev, "if");
> +	if (IS_ERR(priv->iclk)) {
> +		ret = PTR_ERR(priv->iclk);
> +		if (ret != -EPROBE_DEFER)
> +			dev_err(dev, "Failed to get IF clock (ret=%i)\n", ret);
> +		return ret;
> +	}
> +
> +	ret = rcar_gyroadc_parse_subdevs(indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	ret = rcar_gyroadc_init_supplies(indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	priv->model = (enum rcar_gyroadc_model)of_id->data;
> +
> +	platform_set_drvdata(pdev, indio_dev);
> +
> +	indio_dev->name = dev_name(dev);
> +	indio_dev->dev.parent = dev;
> +	indio_dev->dev.of_node = pdev->dev.of_node;
> +	indio_dev->info = &rcar_gyroadc_iio_info;
> +	indio_dev->modes = INDIO_DIRECT_MODE;
> +
> +	pm_runtime_enable(dev);
> +	pm_runtime_get_sync(dev);
> +
> +	ret = clk_prepare_enable(priv->iclk);
> +	if (ret) {
> +		dev_err(dev, "Could not prepare or enable the IF clock.\n");
> +		goto error_clk_if_enable;
> +	}
> +
> +	rcar_gyroadc_hw_init(priv);
This doesn't seem to be unwound on a failure in iio_device_register
in particular the sampling isn't stopped on an error occuring.
> +
> +	ret = iio_device_register(indio_dev);
> +	if (ret) {
> +		dev_err(dev, "Couldn't register IIO device.\n");
> +		goto error_iio_device_register;
> +	}
> +
> +	return 0;
> +
> +error_iio_device_register:
> +	clk_disable_unprepare(priv->iclk);
> +error_clk_if_enable:
> +	pm_runtime_put(dev);
> +	pm_runtime_disable(dev);
> +	rcar_gyroadc_deinit_supplies(indio_dev);
> +	return ret;
> +}
> +
> +static int rcar_gyroadc_remove(struct platform_device *pdev)
> +{
> +	struct iio_dev *indio_dev = platform_get_drvdata(pdev);
> +	struct rcar_gyroadc *priv = iio_priv(indio_dev);
> +	struct device *dev = priv->dev;
> +
> +	/* Stop sampling */
I'd slightly prefer to see this wrapped up in a function that makes it clear
it is unwinding the _init() call made in probe.
Also the ordering of remove should be the reverse of probe which I think
means this should be somewhat later.
> +	writel(0, priv->regs + RCAR_GYROADC_START_STOP);

> +
> +	iio_device_unregister(indio_dev);
> +	clk_disable_unprepare(priv->iclk);
> +	pm_runtime_put(dev);
> +	pm_runtime_disable(dev);
> +	rcar_gyroadc_deinit_supplies(indio_dev);
> +
> +	return 0;
> +}
> +
> +static struct platform_driver rcar_gyroadc_driver = {
> +	.probe          = rcar_gyroadc_probe,
> +	.remove         = rcar_gyroadc_remove,
> +	.driver         = {
> +		.name		= "rcar-gyroadc",
> +		.of_match_table	= rcar_gyroadc_match,
> +	},
> +};
> +
> +module_platform_driver(rcar_gyroadc_driver);
> +
> +MODULE_AUTHOR("Marek Vasut <marek.vasut@xxxxxxxxx>");
> +MODULE_DESCRIPTION("Renesas R-Car GyroADC driver");
> +MODULE_LICENSE("GPL");
> 

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