Re: [PATCH 5/5] iio: adc: stm32: add support for STM32H7

[Jonathan Cameron]

On 19/05/17 13:45, Fabrice Gasnier wrote:
> Add support for STM32H7 Analog to Digital Converter. It has up
> to 20 external channels, resolution ranges from 8 to 16bits.
> Either bus or asynchronous adc clock may be used.
>
> Add registers & bitfields definition. Also add new configuration
> options to enter/exit powerdown and perform self-calibration.
>
> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx>
A couple of trivial bits inline.

Nothing that would prevent me applying this, but I would like to
leave it on the list for a little longer first, purely because
its a substantial addition to the driver, and we might get
some more eyes on it. (I was very close to just taking it but
I'd also like to give time for the devicetree lot to have time
to comment if they wish to.

Do give me a poke if I seem to have forgotten this one
(it wouldn't be the first time that I'd demonstrated that level
of forgetfulness!)

Thanks,

Jonathan
> ---
>   drivers/iio/adc/stm32-adc-core.c | 171 +++++++++++-
>   drivers/iio/adc/stm32-adc-core.h |   2 +
>   drivers/iio/adc/stm32-adc.c      | 552 ++++++++++++++++++++++++++++++++++++++-
>   3 files changed, 721 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/adc/stm32-adc-core.c b/drivers/iio/adc/stm32-adc-core.c
> index c5d292c..e09233b 100644
> --- a/drivers/iio/adc/stm32-adc-core.c
> +++ b/drivers/iio/adc/stm32-adc-core.c
> @@ -49,6 +49,23 @@
>   /* STM32 F4 maximum analog clock rate (from datasheet) */
>   #define STM32F4_ADC_MAX_CLK_RATE	36000000
>   
> +/* STM32H7 - common registers for all ADC instances */
> +#define STM32H7_ADC_CSR			(STM32_ADCX_COMN_OFFSET + 0x00)
> +#define STM32H7_ADC_CCR			(STM32_ADCX_COMN_OFFSET + 0x08)
> +
> +/* STM32H7_ADC_CSR - bit fields */
> +#define STM32H7_EOC_SLV			BIT(18)
> +#define STM32H7_EOC_MST			BIT(2)
> +
> +/* STM32H7_ADC_CCR - bit fields */
> +#define STM32H7_PRESC_SHIFT		18
> +#define STM32H7_PRESC_MASK		GENMASK(21, 18)
> +#define STM32H7_CKMODE_SHIFT		16
> +#define STM32H7_CKMODE_MASK		GENMASK(17, 16)
> +
> +/* STM32 H7 maximum analog clock rate (from datasheet) */
> +#define STM32H7_ADC_MAX_CLK_RATE	72000000
> +
>   /**
>    * stm32_adc_common_regs - stm32 common registers, compatible dependent data
>    * @csr:	common status register offset
> @@ -80,6 +97,7 @@ struct stm32_adc_priv_cfg {
>    * @irq:		irq for ADC block
>    * @domain:		irq domain reference
>    * @aclk:		clock reference for the analog circuitry
> + * @bclk:		bus clock common for all ADCs, depends on part used
>    * @vref:		regulator reference
>    * @cfg:		compatible configuration data
>    * @common:		common data for all ADC instances
> @@ -88,6 +106,7 @@ struct stm32_adc_priv {
>   	int				irq;
>   	struct irq_domain		*domain;
>   	struct clk			*aclk;
> +	struct clk			*bclk;
>   	struct regulator		*vref;
>   	const struct stm32_adc_priv_cfg	*cfg;
>   	struct stm32_adc_common		common;
> @@ -129,6 +148,7 @@ static int stm32f4_adc_clk_sel(struct platform_device *pdev,
>   		return -EINVAL;
>   	}
>   
> +	priv->common.rate = rate;
>   	val = readl_relaxed(priv->common.base + STM32F4_ADC_CCR);
>   	val &= ~STM32F4_ADC_ADCPRE_MASK;
>   	val |= i << STM32F4_ADC_ADCPRE_SHIFT;
> @@ -140,6 +160,111 @@ static int stm32f4_adc_clk_sel(struct platform_device *pdev,
>   	return 0;
>   }
>   
> +/**
> + * struct stm32h7_adc_ck_spec - specification for stm32h7 adc clock
> + * @ckmode: ADC clock mode, Async or sync with prescaler.
> + * @presc: prescaler bitfield for async clock mode
> + * @div: prescaler division ratio
> + */
> +struct stm32h7_adc_ck_spec {
> +	u32 ckmode;
> +	u32 presc;
> +	int div;
> +};
> +
> +const struct stm32h7_adc_ck_spec stm32h7_adc_ckmodes_spec[] = {
> +	/* 00: CK_ADC[1..3]: Asynchronous clock modes */
> +	{ 0, 0, 1 },
> +	{ 0, 1, 2 },
> +	{ 0, 2, 4 },
> +	{ 0, 3, 6 },
> +	{ 0, 4, 8 },
> +	{ 0, 5, 10 },
> +	{ 0, 6, 12 },
> +	{ 0, 7, 16 },
> +	{ 0, 8, 32 },
> +	{ 0, 9, 64 },
> +	{ 0, 10, 128 },
> +	{ 0, 11, 256 },
> +	/* HCLK used: Synchronous clock modes (1, 2 or 4 prescaler) */
> +	{ 1, 0, 1 },
> +	{ 2, 0, 2 },
> +	{ 3, 0, 4 },
> +};
> +
> +static int stm32h7_adc_clk_sel(struct platform_device *pdev,
> +			       struct stm32_adc_priv *priv)
> +{
> +	u32 ckmode, presc, val;
> +	unsigned long rate;
> +	int i, div;
> +
> +	/* stm32h7 bus clock is common for all ADC instances (mandatory) */
> +	if (!priv->bclk) {
> +		dev_err(&pdev->dev, "No 'bus' clock found\n");
> +		return -ENOENT;
> +	}
> +
> +	/*
> +	 * stm32h7 can use either 'bus' or 'adc' clock for analog circuitry.
> +	 * So, choice is to have bus clock mandatory and adc clock optional.
> +	 * If optional 'adc' clock has been found, then try to use it first.
> +	 */
> +	if (priv->aclk) {
> +		/*
> +		 * Asynchronous clock modes (e.g. ckmode == 0)
> +		 * From spec: PLL output musn't exceed max rate
> +		 */
> +		rate = clk_get_rate(priv->aclk);
> +
> +		for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) {
> +			ckmode = stm32h7_adc_ckmodes_spec[i].ckmode;
> +			presc = stm32h7_adc_ckmodes_spec[i].presc;
> +			div = stm32h7_adc_ckmodes_spec[i].div;
> +
> +			if (ckmode)
> +				continue;
> +
> +			if ((rate / div) <= STM32H7_ADC_MAX_CLK_RATE)
> +				goto out;
> +		}
> +	}
> +
> +	/* Synchronous clock modes (e.g. ckmode is 1, 2 or 3) */
> +	rate = clk_get_rate(priv->bclk);
> +
> +	for (i = 0; i < ARRAY_SIZE(stm32h7_adc_ckmodes_spec); i++) {
> +		ckmode = stm32h7_adc_ckmodes_spec[i].ckmode;
> +		presc = stm32h7_adc_ckmodes_spec[i].presc;
> +		div = stm32h7_adc_ckmodes_spec[i].div;
> +
> +		if (!ckmode)
> +			continue;
> +
> +		if ((rate / div) <= STM32H7_ADC_MAX_CLK_RATE)
> +			goto out;
> +	}
> +
> +	dev_err(&pdev->dev, "adc clk selection failed\n");
> +	return -EINVAL;
> +
> +out:
> +	/* rate used later by each ADC instance to control BOOST mode */
> +	priv->common.rate = rate;
> +
> +	/* Set common clock mode and prescaler */
> +	val = readl_relaxed(priv->common.base + STM32H7_ADC_CCR);
> +	val &= ~(STM32H7_CKMODE_MASK | STM32H7_PRESC_MASK);
> +	val |= ckmode << STM32H7_CKMODE_SHIFT;
> +	val |= presc << STM32H7_PRESC_SHIFT;
> +	writel_relaxed(val, priv->common.base + STM32H7_ADC_CCR);
> +
> +	dev_dbg(&pdev->dev, "Using %s clock/%d source at %ld kHz\n",
> +		ckmode ? "bus" : "adc", div, rate / (div * 1000));
> +
> +	return 0;
> +}
> +
>   /* STM32F4 common registers definitions */
>   static const struct stm32_adc_common_regs stm32f4_adc_common_regs = {
>   	.csr = STM32F4_ADC_CSR,
> @@ -148,6 +273,13 @@ static int stm32f4_adc_clk_sel(struct platform_device *pdev,
>   	.eoc3_msk = STM32F4_EOC3,
>   };
>   
> +/* STM32H7 common registers definitions */
> +static const struct stm32_adc_common_regs stm32h7_adc_common_regs = {
> +	.csr = STM32H7_ADC_CSR,
> +	.eoc1_msk = STM32H7_EOC_MST,
> +	.eoc2_msk = STM32H7_EOC_SLV,
> +};
> +
>   /* ADC common interrupt for all instances */
>   static void stm32_adc_irq_handler(struct irq_desc *desc)
>   {
> @@ -291,13 +423,32 @@ static int stm32_adc_probe(struct platform_device *pdev)
>   		}
>   	}
>   
> +	priv->bclk = devm_clk_get(&pdev->dev, "bus");
> +	if (IS_ERR(priv->bclk)) {
> +		ret = PTR_ERR(priv->bclk);
> +		if (ret == -ENOENT) {
> +			priv->bclk = NULL;
> +		} else {
> +			dev_err(&pdev->dev, "Can't get 'bus' clock\n");
> +			goto err_aclk_disable;
> +		}
> +	}
> +
> +	if (priv->bclk) {
> +		ret = clk_prepare_enable(priv->bclk);
> +		if (ret < 0) {
> +			dev_err(&pdev->dev, "adc clk enable failed\n");
> +			goto err_aclk_disable;
> +		}
> +	}
> +
>   	ret = priv->cfg->clk_sel(pdev, priv);
>   	if (ret < 0)
> -		goto err_clk_disable;
> +		goto err_bclk_disable;
>   
>   	ret = stm32_adc_irq_probe(pdev, priv);
>   	if (ret < 0)
> -		goto err_clk_disable;
> +		goto err_bclk_disable;
>   
>   	platform_set_drvdata(pdev, &priv->common);
>   
> @@ -312,7 +463,11 @@ static int stm32_adc_probe(struct platform_device *pdev)
>   err_irq_remove:
>   	stm32_adc_irq_remove(pdev, priv);
>   
> -err_clk_disable:
> +err_bclk_disable:
> +	if (priv->bclk)
> +		clk_disable_unprepare(priv->bclk);
> +
> +err_aclk_disable:
>   	if (priv->aclk)
>   		clk_disable_unprepare(priv->aclk);
>   
> @@ -329,6 +484,8 @@ static int stm32_adc_remove(struct platform_device *pdev)
>   
>   	of_platform_depopulate(&pdev->dev);
>   	stm32_adc_irq_remove(pdev, priv);
> +	if (priv->bclk)
> +		clk_disable_unprepare(priv->bclk);
>   	if (priv->aclk)
>   		clk_disable_unprepare(priv->aclk);
>   	regulator_disable(priv->vref);
> @@ -341,11 +498,19 @@ static int stm32_adc_remove(struct platform_device *pdev)
>   	.clk_sel = stm32f4_adc_clk_sel,
>   };
>   
> +static const struct stm32_adc_priv_cfg stm32h7_adc_priv_cfg = {
> +	.regs = &stm32h7_adc_common_regs,
> +	.clk_sel = stm32h7_adc_clk_sel,
> +};
> +
>   static const struct of_device_id stm32_adc_of_match[] = {
>   	{
>   		.compatible = "st,stm32f4-adc-core",
>   		.data = (void *)&stm32f4_adc_priv_cfg
>   	}, {
> +		.compatible = "st,stm32h7-adc-core",
> +		.data = (void *)&stm32h7_adc_priv_cfg
> +	}, {
>   	},
>   };
>   MODULE_DEVICE_TABLE(of, stm32_adc_of_match);
> diff --git a/drivers/iio/adc/stm32-adc-core.h b/drivers/iio/adc/stm32-adc-core.h
> index 2ec7abb..250ee95 100644
> --- a/drivers/iio/adc/stm32-adc-core.h
> +++ b/drivers/iio/adc/stm32-adc-core.h
> @@ -43,11 +43,13 @@
>    * struct stm32_adc_common - stm32 ADC driver common data (for all instances)
>    * @base:		control registers base cpu addr
>    * @phys_base:		control registers base physical addr
> + * @rate:		clock rate used for analog circuitry
>    * @vref_mv:		vref voltage (mv)
>    */
>   struct stm32_adc_common {
>   	void __iomem			*base;
>   	phys_addr_t			phys_base;
> +	unsigned long			rate;
>   	int				vref_mv;
>   };
>   
> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c
> index ad8fdb9..dba89c7 100644
> --- a/drivers/iio/adc/stm32-adc.c
> +++ b/drivers/iio/adc/stm32-adc.c
> @@ -31,6 +31,7 @@
>   #include <linux/iio/triggered_buffer.h>
>   #include <linux/interrupt.h>
>   #include <linux/io.h>
> +#include <linux/iopoll.h>
>   #include <linux/module.h>
>   #include <linux/platform_device.h>
>   #include <linux/of.h>
> @@ -77,6 +78,78 @@
>   #define STM32F4_DMA			BIT(8)
>   #define STM32F4_ADON			BIT(0)
>   
> +/* STM32H7 - Registers for each ADC instance */
> +#define STM32H7_ADC_ISR			0x00
> +#define STM32H7_ADC_IER			0x04
> +#define STM32H7_ADC_CR			0x08
> +#define STM32H7_ADC_CFGR		0x0C
> +#define STM32H7_ADC_PCSEL		0x1C
> +#define STM32H7_ADC_SQR1		0x30
> +#define STM32H7_ADC_SQR2		0x34
> +#define STM32H7_ADC_SQR3		0x38
> +#define STM32H7_ADC_SQR4		0x3C
> +#define STM32H7_ADC_DR			0x40
> +#define STM32H7_ADC_CALFACT		0xC4
> +#define STM32H7_ADC_CALFACT2		0xC8
> +
> +/* STM32H7_ADC_ISR - bit fields */
> +#define STM32H7_EOC			BIT(2)
> +#define STM32H7_ADRDY			BIT(0)
> +
> +/* STM32H7_ADC_IER - bit fields */
> +#define STM32H7_EOCIE			STM32H7_EOC
> +
> +/* STM32H7_ADC_CR - bit fields */
> +#define STM32H7_ADCAL			BIT(31)
> +#define STM32H7_ADCALDIF		BIT(30)
> +#define STM32H7_DEEPPWD			BIT(29)
> +#define STM32H7_ADVREGEN		BIT(28)
> +#define STM32H7_LINCALRDYW6		BIT(27)
> +#define STM32H7_LINCALRDYW5		BIT(26)
> +#define STM32H7_LINCALRDYW4		BIT(25)
> +#define STM32H7_LINCALRDYW3		BIT(24)
> +#define STM32H7_LINCALRDYW2		BIT(23)
> +#define STM32H7_LINCALRDYW1		BIT(22)
> +#define STM32H7_ADCALLIN		BIT(16)
> +#define STM32H7_BOOST			BIT(8)
> +#define STM32H7_ADSTP			BIT(4)
> +#define STM32H7_ADSTART			BIT(2)
> +#define STM32H7_ADDIS			BIT(1)
> +#define STM32H7_ADEN			BIT(0)
> +
> +/* STM32H7_ADC_CFGR bit fields */
> +#define STM32H7_EXTEN_SHIFT		10
> +#define STM32H7_EXTEN_MASK		GENMASK(11, 10)
> +#define STM32H7_EXTSEL_SHIFT		5
> +#define STM32H7_EXTSEL_MASK		GENMASK(9, 5)
> +#define STM32H7_RES_SHIFT		2
> +#define STM32H7_RES_MASK		GENMASK(4, 2)
> +#define STM32H7_DMNGT_SHIFT		0
> +#define STM32H7_DMNGT_MASK		GENMASK(1, 0)
> +
> +enum stm32h7_adc_dmngt {
> +	STM32H7_DMNGT_DR_ONLY,		/* Regular data in DR only */
> +	STM32H7_DMNGT_DMA_ONESHOT,	/* DMA one shot mode */
> +	STM32H7_DMNGT_DFSDM,		/* DFSDM mode */
> +	STM32H7_DMNGT_DMA_CIRC,		/* DMA circular mode */
> +};
> +
> +/* STM32H7_ADC_CALFACT - bit fields */
> +#define STM32H7_CALFACT_D_SHIFT		16
> +#define STM32H7_CALFACT_D_MASK		GENMASK(26, 16)
> +#define STM32H7_CALFACT_S_SHIFT		0
> +#define STM32H7_CALFACT_S_MASK		GENMASK(10, 0)
> +
> +/* STM32H7_ADC_CALFACT2 - bit fields */
> +#define STM32H7_LINCALFACT_SHIFT	0
> +#define STM32H7_LINCALFACT_MASK		GENMASK(29, 0)
> +
> +/* Number of linear calibration shadow registers / LINCALRDYW control bits */
> +#define STM32H7_LINCALFACT_NUM		6
> +
> +/* BOOST bit must be set on STM32H7 when ADC clock is above 20MHz */
> +#define STM32H7_BOOST_CLKRATE		20000000UL
> +
>   #define STM32_ADC_MAX_SQ		16	/* SQ1..SQ16 */
>   #define STM32_ADC_TIMEOUT_US		100000
>   #define STM32_ADC_TIMEOUT	(msecs_to_jiffies(STM32_ADC_TIMEOUT_US / 1000))
> @@ -122,6 +195,18 @@ struct stm32_adc_trig_info {
>   };
>   
>   /**
> + * struct stm32_adc_calib - optional adc calibration data
> + * @calfact_s: Calibration offset for single ended channels
> + * @calfact_d: Calibration offset in differential
> + * @lincalfact: Linearity calibration factor
> + */
> +struct stm32_adc_calib {
> +	u32			calfact_s;
> +	u32			calfact_d;
> +	u32			lincalfact[STM32H7_LINCALFACT_NUM];
> +};
> +
> +/**
>    * stm32_adc_regs - stm32 ADC misc registers & bitfield desc
>    * @reg:		register offset
>    * @mask:		bitfield mask
> @@ -161,16 +246,22 @@ struct stm32_adc_regspec {
>    * @adc_info:		per instance input channels definitions
>    * @trigs:		external trigger sources
>    * @clk_required:	clock is required
> + * @selfcalib:		optional routine for self-calibration
> + * @prepare:		optional prepare routine (power-up, enable)
>    * @start_conv:		routine to start conversions
>    * @stop_conv:		routine to stop conversions
> + * @unprepare:		optional unprepare routine (disable, power-down)
>    */
>   struct stm32_adc_cfg {
>   	const struct stm32_adc_regspec	*regs;
>   	const struct stm32_adc_info	*adc_info;
>   	struct stm32_adc_trig_info	*trigs;
>   	bool clk_required;
> +	int (*selfcalib)(struct stm32_adc *);
> +	int (*prepare)(struct stm32_adc *);
>   	void (*start_conv)(struct stm32_adc *, bool dma);
>   	void (*stop_conv)(struct stm32_adc *);
> +	void (*unprepare)(struct stm32_adc *);
>   };
>   
>   /**
> @@ -191,6 +282,8 @@ struct stm32_adc_cfg {
>    * @rx_buf:		dma rx buffer cpu address
>    * @rx_dma_buf:		dma rx buffer bus address
>    * @rx_buf_sz:		dma rx buffer size
> + * @pcsel		bitmask to preselect channels on some devices
> + * @cal:		optional calibration data on some devices
>    */
>   struct stm32_adc {
>   	struct stm32_adc_common	*common;
> @@ -209,6 +302,8 @@ struct stm32_adc {
>   	u8			*rx_buf;
>   	dma_addr_t		rx_dma_buf;
>   	unsigned int		rx_buf_sz;
> +	u32			pcsel;
> +	struct stm32_adc_calib	cal;
>   };
>   
>   /**
> @@ -269,6 +364,42 @@ struct stm32_adc_info {
>   	.num_res = ARRAY_SIZE(stm32f4_adc_resolutions),
>   };
>   
> +/* Input definitions for stm32h7 */
> +static const struct stm32_adc_chan_spec stm32h7_adc_channels[] = {
> +	{ IIO_VOLTAGE, 0, "in0" },
> +	{ IIO_VOLTAGE, 1, "in1" },
> +	{ IIO_VOLTAGE, 2, "in2" },
> +	{ IIO_VOLTAGE, 3, "in3" },
> +	{ IIO_VOLTAGE, 4, "in4" },
> +	{ IIO_VOLTAGE, 5, "in5" },
> +	{ IIO_VOLTAGE, 6, "in6" },
> +	{ IIO_VOLTAGE, 7, "in7" },
> +	{ IIO_VOLTAGE, 8, "in8" },
> +	{ IIO_VOLTAGE, 9, "in9" },
> +	{ IIO_VOLTAGE, 10, "in10" },
> +	{ IIO_VOLTAGE, 11, "in11" },
> +	{ IIO_VOLTAGE, 12, "in12" },
> +	{ IIO_VOLTAGE, 13, "in13" },
> +	{ IIO_VOLTAGE, 14, "in14" },
> +	{ IIO_VOLTAGE, 15, "in15" },
> +	{ IIO_VOLTAGE, 16, "in16" },
> +	{ IIO_VOLTAGE, 17, "in17" },
> +	{ IIO_VOLTAGE, 18, "in18" },
> +	{ IIO_VOLTAGE, 19, "in19" },
> +};
It does rather feel like a bit of macro magic would have remove
the need for the third parameter ;)  The first is kind of pointless
currently as well.

It doesn't really matter though, but if you want to send a patch
tidying that up it would be welcome.
> +
> +static const unsigned int stm32h7_adc_resolutions[] = {
> +	/* sorted values so the index matches RES[2:0] in STM32H7_ADC_CFGR */
> +	16, 14, 12, 10, 8,
> +};
> +
> +static const struct stm32_adc_info stm32h7_adc_info = {
> +	.channels = stm32h7_adc_channels,
> +	.max_channels = ARRAY_SIZE(stm32h7_adc_channels),
> +	.resolutions = stm32h7_adc_resolutions,
> +	.num_res = ARRAY_SIZE(stm32h7_adc_resolutions),
> +};
> +
>   /**
>    * stm32f4_sq - describe regular sequence registers
>    * - L: sequence len (register & bit field)
> @@ -327,6 +458,58 @@ struct stm32_adc_info {
>   	.res = { STM32F4_ADC_CR1, STM32F4_RES_MASK, STM32F4_RES_SHIFT },
>   };
>   
> +static const struct stm32_adc_regs stm32h7_sq[STM32_ADC_MAX_SQ + 1] = {
> +	/* L: len bit field description to be kept as first element */
> +	{ STM32H7_ADC_SQR1, GENMASK(3, 0), 0 },
> +	/* SQ1..SQ16 registers & bit fields (reg, mask, shift) */
> +	{ STM32H7_ADC_SQR1, GENMASK(10, 6), 6 },
> +	{ STM32H7_ADC_SQR1, GENMASK(16, 12), 12 },
> +	{ STM32H7_ADC_SQR1, GENMASK(22, 18), 18 },
> +	{ STM32H7_ADC_SQR1, GENMASK(28, 24), 24 },
> +	{ STM32H7_ADC_SQR2, GENMASK(4, 0), 0 },
> +	{ STM32H7_ADC_SQR2, GENMASK(10, 6), 6 },
> +	{ STM32H7_ADC_SQR2, GENMASK(16, 12), 12 },
> +	{ STM32H7_ADC_SQR2, GENMASK(22, 18), 18 },
> +	{ STM32H7_ADC_SQR2, GENMASK(28, 24), 24 },
> +	{ STM32H7_ADC_SQR3, GENMASK(4, 0), 0 },
> +	{ STM32H7_ADC_SQR3, GENMASK(10, 6), 6 },
> +	{ STM32H7_ADC_SQR3, GENMASK(16, 12), 12 },
> +	{ STM32H7_ADC_SQR3, GENMASK(22, 18), 18 },
> +	{ STM32H7_ADC_SQR3, GENMASK(28, 24), 24 },
> +	{ STM32H7_ADC_SQR4, GENMASK(4, 0), 0 },
> +	{ STM32H7_ADC_SQR4, GENMASK(10, 6), 6 },
> +};
> +
> +/* STM32H7 external trigger sources for all instances */
> +static struct stm32_adc_trig_info stm32h7_adc_trigs[] = {
> +	{ TIM1_CH1, STM32_EXT0 },
> +	{ TIM1_CH2, STM32_EXT1 },
> +	{ TIM1_CH3, STM32_EXT2 },
> +	{ TIM2_CH2, STM32_EXT3 },
> +	{ TIM3_TRGO, STM32_EXT4 },
> +	{ TIM4_CH4, STM32_EXT5 },
> +	{ TIM8_TRGO, STM32_EXT7 },
> +	{ TIM8_TRGO2, STM32_EXT8 },
> +	{ TIM1_TRGO, STM32_EXT9 },
> +	{ TIM1_TRGO2, STM32_EXT10 },
> +	{ TIM2_TRGO, STM32_EXT11 },
> +	{ TIM4_TRGO, STM32_EXT12 },
> +	{ TIM6_TRGO, STM32_EXT13 },
> +	{ TIM3_CH4, STM32_EXT15 },
> +	{},
> +};
> +
> +static const struct stm32_adc_regspec stm32h7_adc_regspec = {
> +	.dr = STM32H7_ADC_DR,
> +	.ier_eoc = { STM32H7_ADC_IER, STM32H7_EOCIE },
> +	.isr_eoc = { STM32H7_ADC_ISR, STM32H7_EOC },
> +	.sqr = stm32h7_sq,
> +	.exten = { STM32H7_ADC_CFGR, STM32H7_EXTEN_MASK, STM32H7_EXTEN_SHIFT },
> +	.extsel = { STM32H7_ADC_CFGR, STM32H7_EXTSEL_MASK,
> +		    STM32H7_EXTSEL_SHIFT },
> +	.res = { STM32H7_ADC_CFGR, STM32H7_RES_MASK, STM32H7_RES_SHIFT },
> +};
> +
>   /**
>    * STM32 ADC registers access routines
>    * @adc: stm32 adc instance
> @@ -340,6 +523,12 @@ static u32 stm32_adc_readl(struct stm32_adc *adc, u32 reg)
>   	return readl_relaxed(adc->common->base + adc->offset + reg);
>   }
>   
> +#define stm32_adc_readl_addr(addr)	stm32_adc_readl(adc, addr)
> +
> +#define stm32_adc_readl_poll_timeout(reg, val, cond, sleep_us, timeout_us) \
> +	readx_poll_timeout(stm32_adc_readl_addr, reg, val, \
> +			   cond, sleep_us, timeout_us)
> +
>   static u16 stm32_adc_readw(struct stm32_adc *adc, u32 reg)
>   {
>   	return readw_relaxed(adc->common->base + adc->offset + reg);
> @@ -436,6 +625,324 @@ static void stm32f4_adc_stop_conv(struct stm32_adc *adc)
>   			   STM32F4_ADON | STM32F4_DMA | STM32F4_DDS);
>   }
>   
> +static void stm32h7_adc_start_conv(struct stm32_adc *adc, bool dma)
> +{
> +	enum stm32h7_adc_dmngt dmngt;
> +	unsigned long flags;
> +	u32 val;
> +
> +	if (dma)
> +		dmngt = STM32H7_DMNGT_DMA_CIRC;
> +	else
> +		dmngt = STM32H7_DMNGT_DR_ONLY;
> +
> +	spin_lock_irqsave(&adc->lock, flags);
> +	val = stm32_adc_readl(adc, STM32H7_ADC_CFGR);
> +	val = (val & ~STM32H7_DMNGT_MASK) | (dmngt << STM32H7_DMNGT_SHIFT);
> +	stm32_adc_writel(adc, STM32H7_ADC_CFGR, val);
> +	spin_unlock_irqrestore(&adc->lock, flags);
> +
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADSTART);
> +}
> +
> +static void stm32h7_adc_stop_conv(struct stm32_adc *adc)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +	int ret;
> +	u32 val;
> +
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADSTP);
> +
> +	ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +					   !(val & (STM32H7_ADSTART)),
> +					   100, STM32_ADC_TIMEOUT_US);
> +	if (ret)
> +		dev_warn(&indio_dev->dev, "stop failed\n");
> +
> +	stm32_adc_clr_bits(adc, STM32H7_ADC_CFGR, STM32H7_DMNGT_MASK);
> +}
> +
> +static void stm32h7_adc_exit_pwr_down(struct stm32_adc *adc)
> +{
> +	/* Exit deep power down, then enable ADC voltage regulator */
> +	stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_DEEPPWD);
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADVREGEN);
> +
> +	if (adc->common->rate > STM32H7_BOOST_CLKRATE)
> +		stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_BOOST);
> +
> +	/* Wait for startup time */
> +	usleep_range(10, 20);
> +}
> +
> +static void stm32h7_adc_enter_pwr_down(struct stm32_adc *adc)
> +{
> +	stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_BOOST);
> +
> +	/* Setting DEEPPWD disables ADC vreg and clears ADVREGEN */
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_DEEPPWD);
> +}
> +
> +static int stm32h7_adc_enable(struct stm32_adc *adc)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +	int ret;
> +	u32 val;
> +
> +	/* Clear ADRDY by writing one, then enable ADC */
> +	stm32_adc_set_bits(adc, STM32H7_ADC_ISR, STM32H7_ADRDY);
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADEN);
> +
> +	/* Poll for ADRDY to be set (after adc startup time) */
> +	ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_ISR, val,
> +					   val & STM32H7_ADRDY,
> +					   100, STM32_ADC_TIMEOUT_US);
> +	if (ret) {
> +		stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_ADEN);
> +		dev_err(&indio_dev->dev, "Failed to enable ADC\n");
> +	}
> +
> +	return ret;
> +}
> +
> +static void stm32h7_adc_disable(struct stm32_adc *adc)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +	int ret;
> +	u32 val;
> +
> +	/* Disable ADC and wait until it's effectively disabled */
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADDIS);
> +	ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +					   !(val & STM32H7_ADEN), 100,
> +					   STM32_ADC_TIMEOUT_US);
> +	if (ret)
> +		dev_warn(&indio_dev->dev, "Failed to disable\n");
> +}
> +
> +/**
> + * stm32h7_adc_read_selfcalib() - read calibration shadow regs, save result
> + * @adc: stm32 adc instance
> + */
> +static int stm32h7_adc_read_selfcalib(struct stm32_adc *adc)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +	int i, ret;
> +	u32 lincalrdyw_mask, val;
> +
> +	/* Enable adc so LINCALRDYW1..6 bits are writable */
> +	ret = stm32h7_adc_enable(adc);
> +	if (ret)
> +		return ret;
> +
> +	/* Read linearity calibration */
> +	lincalrdyw_mask = STM32H7_LINCALRDYW6;
> +	for (i = STM32H7_LINCALFACT_NUM - 1; i >= 0; i--) {
> +		/* Clear STM32H7_LINCALRDYW[6..1]: transfer calib to CALFACT2 */
> +		stm32_adc_clr_bits(adc, STM32H7_ADC_CR, lincalrdyw_mask);
> +
> +		/* Poll: wait calib data to be ready in CALFACT2 register */
> +		ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +						   !(val & lincalrdyw_mask),
> +						   100, STM32_ADC_TIMEOUT_US);
> +		if (ret) {
> +			dev_err(&indio_dev->dev, "Failed to read calfact\n");
> +			goto disable;
> +		}
> +
> +		val = stm32_adc_readl(adc, STM32H7_ADC_CALFACT2);
> +		adc->cal.lincalfact[i] = (val & STM32H7_LINCALFACT_MASK);
> +		adc->cal.lincalfact[i] >>= STM32H7_LINCALFACT_SHIFT;
> +
> +		lincalrdyw_mask >>= 1;
> +	}
> +
> +	/* Read offset calibration */
> +	val = stm32_adc_readl(adc, STM32H7_ADC_CALFACT);
> +	adc->cal.calfact_s = (val & STM32H7_CALFACT_S_MASK);
> +	adc->cal.calfact_s >>= STM32H7_CALFACT_S_SHIFT;
> +	adc->cal.calfact_d = (val & STM32H7_CALFACT_D_MASK);
> +	adc->cal.calfact_d >>= STM32H7_CALFACT_D_SHIFT;
> +
> +disable:
> +	stm32h7_adc_disable(adc);
> +
> +	return ret;
> +}
> +
> +/**
> + * stm32h7_adc_restore_selfcalib() - Restore saved self-calibration result
> + * @adc: stm32 adc instance
> + * Note: ADC must be enabled, with no on-going conversions.
> + */
> +static int stm32h7_adc_restore_selfcalib(struct stm32_adc *adc)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +	int i, ret;
> +	u32 lincalrdyw_mask, val;
> +
> +	val = (adc->cal.calfact_s << STM32H7_CALFACT_S_SHIFT) |
> +		(adc->cal.calfact_d << STM32H7_CALFACT_D_SHIFT);
> +	stm32_adc_writel(adc, STM32H7_ADC_CALFACT, val);
> +
> +	lincalrdyw_mask = STM32H7_LINCALRDYW6;
> +	for (i = STM32H7_LINCALFACT_NUM - 1; i >= 0; i--) {
> +		/*
> +		 * Write saved calibration data to shadow registers:
> +		 * Write CALFACT2, and set LINCALRDYW[6..1] bit to trigger
> +		 * data write. Then poll to wait for complete transfer.
> +		 */
> +		val = adc->cal.lincalfact[i] << STM32H7_LINCALFACT_SHIFT;
> +		stm32_adc_writel(adc, STM32H7_ADC_CALFACT2, val);
> +		stm32_adc_set_bits(adc, STM32H7_ADC_CR, lincalrdyw_mask);
> +		ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +						   val & lincalrdyw_mask,
> +						   100, STM32_ADC_TIMEOUT_US);
> +		if (ret) {
> +			dev_err(&indio_dev->dev, "Failed to write calfact\n");
> +			return ret;
> +		}
> +
> +		/*
> +		 * Read back calibration data, has two effects:
> +		 * - It ensures bits LINCALRDYW[6..1] are kept cleared
> +		 *   for next time calibration needs to be restored.
> +		 * - BTW, bit clear triggers a read, then check data has been
> +		 *   correctly written.
> +		 */
> +		stm32_adc_clr_bits(adc, STM32H7_ADC_CR, lincalrdyw_mask);
> +		ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +						   !(val & lincalrdyw_mask),
> +						   100, STM32_ADC_TIMEOUT_US);
> +		if (ret) {
> +			dev_err(&indio_dev->dev, "Failed to read calfact\n");
> +			return ret;
> +		}
> +		val = stm32_adc_readl(adc, STM32H7_ADC_CALFACT2);
> +		if (val != adc->cal.lincalfact[i] << STM32H7_LINCALFACT_SHIFT) {
> +			dev_err(&indio_dev->dev, "calfact not consistent\n");
> +			return -EIO;
> +		}
> +
> +		lincalrdyw_mask >>= 1;
> +	}
> +
> +	return 0;
> +}
> +
> +/**
> + * Fixed timeout value for ADC calibration.
> + * worst cases:
> + * - low clock frequency
> + * - maximum prescalers
> + * Calibration requires:
> + * - 131,072 ADC clock cycle for the linear calibration
> + * - 20 ADC clock cycle for the offset calibration
> + *
> + * Set to 100ms for now
> + */
> +#define STM32H7_ADC_CALIB_TIMEOUT_US		100000
> +
> +/**
> + * stm32h7_adc_selfcalib() - Procedure to calibrate ADC (from power down)
> + * @adc: stm32 adc instance
> + * Exit from power down, calibrate ADC, then return to power down.
> + */
> +static int stm32h7_adc_selfcalib(struct stm32_adc *adc)
> +{
> +	struct iio_dev *indio_dev = iio_priv_to_dev(adc);
> +	int ret;
> +	u32 val;
> +
> +	stm32h7_adc_exit_pwr_down(adc);
> +
> +	/*
> +	 * Select calibration mode:
> +	 * - Offset calibration for single ended inputs
> +	 * - No linearity calibration (do it later, before reading it)
> +	 */
> +	stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_ADCALDIF);
> +	stm32_adc_clr_bits(adc, STM32H7_ADC_CR, STM32H7_ADCALLIN);
> +
> +	/* Start calibration, then wait for completion */
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADCAL);
> +	ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +					   !(val & STM32H7_ADCAL), 100,
> +					   STM32H7_ADC_CALIB_TIMEOUT_US);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "calibration failed\n");
> +		goto pwr_dwn;
> +	}
> +
> +	/*
> +	 * Select calibration mode, then start calibration:
> +	 * - Offset calibration for differential input
> +	 * - Linearity calibration (needs to be done only once for single/diff)
> +	 *   will run simultaneously with offset calibration.
> +	 */
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR,
> +			   STM32H7_ADCALDIF | STM32H7_ADCALLIN);
> +	stm32_adc_set_bits(adc, STM32H7_ADC_CR, STM32H7_ADCAL);
> +	ret = stm32_adc_readl_poll_timeout(STM32H7_ADC_CR, val,
> +					   !(val & STM32H7_ADCAL), 100,
> +					   STM32H7_ADC_CALIB_TIMEOUT_US);
> +	if (ret) {
> +		dev_err(&indio_dev->dev, "calibration failed\n");
> +		goto pwr_dwn;
> +	}
> +
> +	stm32_adc_clr_bits(adc, STM32H7_ADC_CR,
> +			   STM32H7_ADCALDIF | STM32H7_ADCALLIN);
> +
> +	/* Read calibration result for future reference */
> +	ret = stm32h7_adc_read_selfcalib(adc);
> +
> +pwr_dwn:
> +	stm32h7_adc_enter_pwr_down(adc);
> +
> +	return ret;
> +}
> +
> +/**
> + * stm32h7_adc_prepare() - Leave power down mode to enable ADC.
> + * @adc: stm32 adc instance
> + * Leave power down mode.
> + * Enable ADC.
> + * Restore calibration data.
> + * Pre-select channels that may be used in PCSEL (required by input MUX / IO).
> + */
> +static int stm32h7_adc_prepare(struct stm32_adc *adc)
> +{
> +	int ret;
> +
> +	stm32h7_adc_exit_pwr_down(adc);
> +
> +	ret = stm32h7_adc_enable(adc);
> +	if (ret)
> +		goto pwr_dwn;
> +
> +	ret = stm32h7_adc_restore_selfcalib(adc);
> +	if (ret)
> +		goto disable;
> +
> +	stm32_adc_writel(adc, STM32H7_ADC_PCSEL, adc->pcsel);
> +
> +	return 0;
> +
> +disable:
> +	stm32h7_adc_disable(adc);
> +pwr_dwn:
> +	stm32h7_adc_enter_pwr_down(adc);
> +
> +	return ret;
> +}
> +
> +static void stm32h7_adc_unprepare(struct stm32_adc *adc)
> +{
> +	stm32h7_adc_disable(adc);
> +	stm32h7_adc_enter_pwr_down(adc);
> +}
> +
>   /**
>    * stm32_adc_conf_scan_seq() - Build regular channels scan sequence
>    * @indio_dev: IIO device
> @@ -606,6 +1113,12 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev,
>   
>   	adc->bufi = 0;
>   
> +	if (adc->cfg->prepare) {
> +		ret = adc->cfg->prepare(adc);
> +		if (ret)
> +			return ret;
> +	}
> +
>   	/* Program chan number in regular sequence (SQ1) */
>   	val = stm32_adc_readl(adc, regs->sqr[1].reg);
>   	val &= ~regs->sqr[1].mask;
> @@ -637,6 +1150,9 @@ static int stm32_adc_single_conv(struct iio_dev *indio_dev,
>   
>   	stm32_adc_conv_irq_disable(adc);
>   
> +	if (adc->cfg->unprepare)
> +		adc->cfg->unprepare(adc);
> +
>   	return ret;
>   }
>   
> @@ -861,10 +1377,16 @@ static int stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
>   	struct stm32_adc *adc = iio_priv(indio_dev);
>   	int ret;
>   
> +	if (adc->cfg->prepare) {
> +		ret = adc->cfg->prepare(adc);
> +		if (ret)
> +			return ret;
> +	}
> +
>   	ret = stm32_adc_set_trig(indio_dev, indio_dev->trig);
>   	if (ret) {
>   		dev_err(&indio_dev->dev, "Can't set trigger\n");
> -		return ret;
> +		goto err_unprepare;
>   	}
>   
>   	ret = stm32_adc_dma_start(indio_dev);
> @@ -892,6 +1414,9 @@ static int stm32_adc_buffer_postenable(struct iio_dev *indio_dev)
>   		dmaengine_terminate_all(adc->dma_chan);
>   err_clr_trig:
>   	stm32_adc_set_trig(indio_dev, NULL);
> +err_unprepare:
> +	if (adc->cfg->unprepare)
> +		adc->cfg->unprepare(adc);
>   
>   	return ret;
>   }
> @@ -915,6 +1440,9 @@ static int stm32_adc_buffer_predisable(struct iio_dev *indio_dev)
>   	if (stm32_adc_set_trig(indio_dev, NULL))
>   		dev_err(&indio_dev->dev, "Can't clear trigger\n");
>   
> +	if (adc->cfg->unprepare)
> +		adc->cfg->unprepare(adc);
> +
>   	return ret;
>   }
>   
> @@ -1002,6 +1530,7 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
>   {
>   	struct stm32_adc *adc = iio_priv(indio_dev);
>   
> +	/* Initialize IIO channel */
If I was being really really fussy, this comment shouldn't be in this patch.
Nothing wrong with it, but it isn't what this patch is about.
>   	chan->type = channel->type;
>   	chan->channel = channel->channel;
>   	chan->datasheet_name = channel->name;
> @@ -1013,6 +1542,9 @@ static void stm32_adc_chan_init_one(struct iio_dev *indio_dev,
>   	chan->scan_type.realbits = adc->cfg->adc_info->resolutions[adc->res];
>   	chan->scan_type.storagebits = 16;
>   	chan->ext_info = stm32_adc_ext_info;
> +
> +	/* pre-build selected channels mask */
> +	adc->pcsel |= BIT(chan->channel);
>   }
>   
>   static int stm32_adc_chan_of_init(struct iio_dev *indio_dev)
> @@ -1166,6 +1698,12 @@ static int stm32_adc_probe(struct platform_device *pdev)
>   		goto err_clk_disable;
>   	stm32_adc_set_res(adc);
>   
> +	if (adc->cfg->selfcalib) {
> +		ret = adc->cfg->selfcalib(adc);
> +		if (ret)
> +			goto err_clk_disable;
> +	}
> +
>   	ret = stm32_adc_chan_of_init(indio_dev);
>   	if (ret < 0)
>   		goto err_clk_disable;
> @@ -1236,8 +1774,20 @@ static int stm32_adc_remove(struct platform_device *pdev)
>   	.stop_conv = stm32f4_adc_stop_conv,
>   };
>   
> +static const struct stm32_adc_cfg stm32h7_adc_cfg = {
> +	.regs = &stm32h7_adc_regspec,
> +	.adc_info = &stm32h7_adc_info,
> +	.trigs = stm32h7_adc_trigs,
> +	.selfcalib = stm32h7_adc_selfcalib,
> +	.start_conv = stm32h7_adc_start_conv,
> +	.stop_conv = stm32h7_adc_stop_conv,
> +	.prepare = stm32h7_adc_prepare,
> +	.unprepare = stm32h7_adc_unprepare,
> +};
> +
>   static const struct of_device_id stm32_adc_of_match[] = {
>   	{ .compatible = "st,stm32f4-adc", .data = (void *)&stm32f4_adc_cfg },
> +	{ .compatible = "st,stm32h7-adc", .data = (void *)&stm32h7_adc_cfg },
>   	{},
>   };
>   MODULE_DEVICE_TABLE(of, stm32_adc_of_match);