Message-ID: <20210329115826.03bc5745@jic23-huawei>
Date:   Mon, 29 Mar 2021 11:58:26 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Oleksij Rempel <o.rempel@...gutronix.de>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>,
        Robin van der Gracht <robin@...tonic.nl>,
        linux-iio@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>
Subject: Re: [PATCH v5 3/3] iio: adc: add ADC driver for the TI TSC2046
 controller

On Mon, 29 Mar 2021 09:31:31 +0200
Oleksij Rempel <o.rempel@...gutronix.de> wrote:

> Basically the TI TSC2046 touchscreen controller is 8 channel ADC optimized for
> the touchscreen use case. By implementing it as an IIO ADC device, we can
> make use of resistive-adc-touch and iio-hwmon drivers.
> 
> Polled readings are currently not implemented to keep this patch small, so
> iio-hwmon will not work out of the box for now.
> 
> So far, this driver was tested with a custom version of resistive-adc-touch driver,
> since it needs to be extended to make use of Z1 and Z2 channels. The X/Y
> are working without additional changes.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Hi Oleksij,

Couple of things in here I missed before, but big question is still whether
Dmitry is happy with what you mention in the cover letter:

"This driver can replace drivers/input/touchscreen/ads7846.c and has
following advantages over it:
- less code to maintain
- shared code paths (resistive-adc-touch, iio-hwmon, etc)
- can be used as plain IIO ADC to investigate signaling issues or test
  real capacity of the plates and attached low-pass filters
  (or use the touchscreen as a microphone if you like ;) )"

So two things that need addressing in here are
iio_dev->name (part number, not hybrid of that an spi device name)
Why oversampling is DT rather than userspace controllable.
For that I'm looking for clear reasoning for the choice.

Thanks,

Jonathan



> ---
>  MAINTAINERS                  |   8 +
>  drivers/iio/adc/Kconfig      |  12 +
>  drivers/iio/adc/Makefile     |   1 +
>  drivers/iio/adc/ti-tsc2046.c | 726 +++++++++++++++++++++++++++++++++++
>  4 files changed, 747 insertions(+)
>  create mode 100644 drivers/iio/adc/ti-tsc2046.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 9a9bf18bba00..e288fae26cde 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -18013,6 +18013,14 @@ S:	Supported
>  F:	Documentation/devicetree/bindings/net/nfc/trf7970a.txt
>  F:	drivers/nfc/trf7970a.c
>  
> +TI TSC2046 ADC DRIVER
> +M:	Oleksij Rempel <o.rempel@...gutronix.de>
> +R:	kernel@...gutronix.de
> +L:	linux-iio@...r.kernel.org
> +S:	Maintained
> +F:	Documentation/devicetree/bindings/iio/adc/ti,tsc2046.yaml
> +F:	drivers/iio/adc/ti-tsc2046.c
> +
>  TI TWL4030 SERIES SOC CODEC DRIVER
>  M:	Peter Ujfalusi <peter.ujfalusi@...il.com>
>  L:	alsa-devel@...a-project.org (moderated for non-subscribers)
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 769381b05b9a..6fe8d1046b4b 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -1188,6 +1188,18 @@ config TI_TLC4541
>  	  This driver can also be built as a module. If so, the module will be
>  	  called ti-tlc4541.
>  
> +config TI_TSC2046
> +	tristate "Texas Instruments TSC2046 ADC driver"
> +	depends on SPI
> +	select IIO_BUFFER
> +	select IIO_TRIGGERED_BUFFER
> +	help
> +	  Say yes here to build support for ADC functionality of Texas
> +	  Instruments TSC2046 touch screen controller.
> +
> +	  This driver can also be built as a module. If so, the module will be
> +	  called ti-tsc2046.
> +
>  config TWL4030_MADC
>  	tristate "TWL4030 MADC (Monitoring A/D Converter)"
>  	depends on TWL4030_CORE
> diff --git a/drivers/iio/adc/Makefile b/drivers/iio/adc/Makefile
> index a226657d19c0..f70d877c555a 100644
> --- a/drivers/iio/adc/Makefile
> +++ b/drivers/iio/adc/Makefile
> @@ -106,6 +106,7 @@ obj-$(CONFIG_TI_ADS124S08) += ti-ads124s08.o
>  obj-$(CONFIG_TI_ADS131E08) += ti-ads131e08.o
>  obj-$(CONFIG_TI_AM335X_ADC) += ti_am335x_adc.o
>  obj-$(CONFIG_TI_TLC4541) += ti-tlc4541.o
> +obj-$(CONFIG_TI_TSC2046) += ti-tsc2046.o
>  obj-$(CONFIG_TWL4030_MADC) += twl4030-madc.o
>  obj-$(CONFIG_TWL6030_GPADC) += twl6030-gpadc.o
>  obj-$(CONFIG_VF610_ADC) += vf610_adc.o
> diff --git a/drivers/iio/adc/ti-tsc2046.c b/drivers/iio/adc/ti-tsc2046.c
> new file mode 100644
> index 000000000000..7fe3c677ab1c
> --- /dev/null
> +++ b/drivers/iio/adc/ti-tsc2046.c
> @@ -0,0 +1,726 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Texas Instruments TSC2046 SPI ADC driver
> + *
> + * Copyright (c) 2021 Oleksij Rempel <kernel@...gutronix.de>, Pengutronix
> + */
> +
> +#include <linux/bitfield.h>
> +#include <linux/delay.h>
> +#include <linux/module.h>
> +#include <linux/spi/spi.h>
> +
> +#include <asm/unaligned.h>
> +
> +#include <linux/iio/buffer.h>
> +#include <linux/iio/trigger_consumer.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger.h>
> +
> +/*
> + * The PENIRQ of TSC2046 controller is implemented as level shifter attached to
> + * the X+ line. If voltage of the X+ line reaches a specific level the IRQ will
> + * be activated or deactivated.
> + * To make this kind of IRQ reusable as trigger following additions were
> + * implemented:
> + * - rate limiting:
> + *   For typical touchscreen use case, we need to trigger about each 10ms.
> + * - hrtimer:
> + *   Continue triggering at least once after the IRQ was deactivated. Then
> + *   deactivate this trigger to stop sampling in order to reduce power
> + *   consumption.
> + */
> +
> +#define TI_TSC2046_NAME				"tsc2046"
> +
> +/* This driver doesn't aim at the peak continuous sample rate */
> +#define	TI_TSC2046_MAX_SAMPLE_RATE		125000
> +#define	TI_TSC2046_SAMPLE_BITS \
> +	BITS_PER_TYPE(struct tsc2046_adc_atom)
> +#define	TI_TSC2046_MAX_CLK_FREQ \
> +	(TI_TSC2046_MAX_SAMPLE_RATE * TI_TSC2046_SAMPLE_BITS)
> +
> +#define TI_TSC2046_SAMPLE_INTERVAL_US		10000
> +
> +#define TI_TSC2046_START			BIT(7)
> +#define TI_TSC2046_ADDR				GENMASK(6, 4)
> +#define TI_TSC2046_ADDR_TEMP1			7
> +#define TI_TSC2046_ADDR_AUX			6
> +#define TI_TSC2046_ADDR_X			5
> +#define TI_TSC2046_ADDR_Z2			4
> +#define TI_TSC2046_ADDR_Z1			3
> +#define TI_TSC2046_ADDR_VBAT			2
> +#define TI_TSC2046_ADDR_Y			1
> +#define TI_TSC2046_ADDR_TEMP0			0
> +
> +/*
> + * The mode bit sets the resolution of the ADC. With this bit low, the next
> + * conversion has 12-bit resolution, whereas with this bit high, the next
> + * conversion has 8-bit resolution. This driver is optimized for 12-bit mode.
> + * So, for this driver, this bit should stay zero.
> + */
> +#define TI_TSC2046_8BIT_MODE			BIT(3)
> +
> +/*
> + * SER/DFR - The SER/DFR bit controls the reference mode, either single-ended
> + * (high) or differential (low).
> + */
> +#define TI_TSC2046_SER				BIT(2)
> +
> +/*
> + * If VREF_ON and ADC_ON are both zero, then the chip operates in
> + * auto-wake/suspend mode. In most case this bits should stay zero.
> + */
> +#define TI_TSC2046_PD1_VREF_ON			BIT(1)
> +#define TI_TSC2046_PD0_ADC_ON			BIT(0)
> +
> +/*
> + * All supported devices can do 8 or 12bit resolution. This driver
> + * supports only 12bit mode, here we have a 16bit data transfer, where
> + * the MSB and the 3 LSB are 0.
> + */
> +#define TI_TSC2046_DATA_12BIT			GENMASK(14, 3)
> +
> +#define TI_TSC2046_MAX_CHAN			8
> +
> +/* Represents a HW sample */
> +struct tsc2046_adc_atom {
> +	/*
> +	 * Command transmitted to the controller. This field is empty on the RX
> +	 * buffer.
> +	 */
> +	u8 cmd;
> +	/*
> +	 * Data received from the controller. This field is empty for the TX
> +	 * buffer
> +	 */
> +	__be16 data;
> +} __packed;
> +
> +/* Layout of atomic buffers within big buffer */
> +struct tsc2046_adc_group_layout {
> +	/* Group offset within the SPI RX buffer */
> +	unsigned int offset;
> +	/*
> +	 * Amount of tsc2046_adc_atom structs within the same command gathered
> +	 * within same group.
> +	 */
> +	unsigned int count;
> +	/*
> +	 * Settling samples (tsc2046_adc_atom structs) which should be skipped
> +	 * before good samples will start.
> +	 */
> +	unsigned int skip;
> +};
> +
> +struct tsc2046_adc_dcfg {
> +	const struct iio_chan_spec *channels;
> +	unsigned int num_channels;
> +};
> +
> +struct tsc2046_adc_ch_cfg {
> +	unsigned int settling_time_us;
> +	unsigned int oversampling_ratio;
> +};
> +
> +struct tsc2046_adc_priv {
> +	struct spi_device *spi;
> +	const struct tsc2046_adc_dcfg *dcfg;
> +
> +	struct iio_trigger *trig;
> +	struct hrtimer trig_timer;
> +	spinlock_t trig_lock;
> +	unsigned int trig_more_count;
> +
> +	struct spi_transfer xfer;
> +	struct spi_message msg;
> +
> +	struct {
> +		/* Scan data for each channel */
> +		u16 data[TI_TSC2046_MAX_CHAN];
> +		/* Timestamp */
> +		s64 ts __aligned(8);
> +	} scan_buf;
> +
> +	/*
> +	 * Lock to protect the layout and the SPI transfer buffer.
> +	 * tsc2046_adc_group_layout can be changed within update_scan_mode(),
> +	 * in this case the l[] and tx/rx buffer will be out of sync to each
> +	 * other.
> +	 */
> +	struct mutex slock;
> +	struct tsc2046_adc_group_layout l[TI_TSC2046_MAX_CHAN];
> +	struct tsc2046_adc_atom *rx;
> +	struct tsc2046_adc_atom *tx;
> +
> +	struct tsc2046_adc_atom *rx_one;
> +	struct tsc2046_adc_atom *tx_one;
> +
> +	unsigned int count;
> +	unsigned int groups;
> +	u32 effective_speed_hz;
> +	u32 scan_interval_us;
> +	u32 time_per_scan_us;
> +	u32 time_per_bit_ns;
> +
> +	struct tsc2046_adc_ch_cfg ch_cfg[TI_TSC2046_MAX_CHAN];
> +};
> +
> +#define TI_TSC2046_V_CHAN(index, bits, name)			\
> +{								\
> +	.type = IIO_VOLTAGE,					\
> +	.indexed = 1,						\
> +	.channel = index,					\
> +	.datasheet_name = "#name",				\
> +	.scan_index = index,					\
> +	.scan_type = {						\
> +		.sign = 'u',					\
> +		.realbits = bits,				\
> +		.storagebits = 16,				\
> +		.endianness = IIO_CPU,				\
> +	},							\
> +}
> +
> +#define DECLARE_TI_TSC2046_8_CHANNELS(name, bits) \
> +const struct iio_chan_spec name ## _channels[] = { \
> +	TI_TSC2046_V_CHAN(0, bits, TEMP0), \
> +	TI_TSC2046_V_CHAN(1, bits, Y), \
> +	TI_TSC2046_V_CHAN(2, bits, VBAT), \
> +	TI_TSC2046_V_CHAN(3, bits, Z1), \
> +	TI_TSC2046_V_CHAN(4, bits, Z2), \
> +	TI_TSC2046_V_CHAN(5, bits, X), \
> +	TI_TSC2046_V_CHAN(6, bits, AUX), \
> +	TI_TSC2046_V_CHAN(7, bits, TEMP1), \
> +	IIO_CHAN_SOFT_TIMESTAMP(8), \
> +}
> +
> +static DECLARE_TI_TSC2046_8_CHANNELS(tsc2046_adc, 12);
> +
> +static const struct tsc2046_adc_dcfg tsc2046_adc_dcfg_tsc2046e = {
> +	.channels = tsc2046_adc_channels,
> +	.num_channels = ARRAY_SIZE(tsc2046_adc_channels),
> +};
> +
> +/*
> + * Convert time to a number of samples which can be transferred within this
> + * time.
> + */
> +static unsigned int tsc2046_adc_time_to_count(struct tsc2046_adc_priv *priv,
> +					      unsigned long time)
> +{
> +	unsigned int bit_count, sample_count;
> +
> +	bit_count = DIV_ROUND_UP(time * NSEC_PER_USEC, priv->time_per_bit_ns);
> +	sample_count = DIV_ROUND_UP(bit_count, TI_TSC2046_SAMPLE_BITS);
> +
> +	dev_dbg(&priv->spi->dev, "Effective speed %u, time per bit: %u, count bits: %u, count samples: %u\n",
> +		priv->effective_speed_hz, priv->time_per_bit_ns,
> +		bit_count, sample_count);
> +
> +	return sample_count;
> +}
> +
> +static u8 tsc2046_adc_get_cmd(struct tsc2046_adc_priv *priv, int ch_idx,
> +			      bool keep_power)
> +{
> +	u32 pd;
> +
> +	/*
> +	 * if PD bits are 0, controller will automatically disable ADC, VREF and
> +	 * enable IRQ.
> +	 */
> +	if (keep_power)
> +		pd = TI_TSC2046_PD0_ADC_ON;
> +	else
> +		pd = 0;
> +
> +	return TI_TSC2046_START | FIELD_PREP(TI_TSC2046_ADDR, ch_idx) | pd;
> +}
> +
> +static u16 tsc2046_adc_get_value(struct tsc2046_adc_atom *buf)
> +{
> +	return FIELD_GET(TI_TSC2046_DATA_12BIT, get_unaligned_be16(&buf->data));
> +}
> +
> +static int tsc2046_adc_read_one(struct tsc2046_adc_priv *priv, int ch_idx,
> +				u32 *effective_speed_hz)
> +{
> +	struct spi_transfer xfer;
> +	struct spi_message msg;
> +	int ret;
> +
> +	memset(&xfer, 0, sizeof(xfer));
> +	priv->tx_one->cmd = tsc2046_adc_get_cmd(priv, ch_idx, false);
> +	priv->tx_one->data = 0;
> +	xfer.tx_buf = priv->tx_one;
> +	xfer.rx_buf = priv->rx_one;
> +	xfer.len = sizeof(*priv->tx_one);
> +	spi_message_init(&msg);
> +	spi_message_add_tail(&xfer, &msg);
> +
> +	/*
> +	 * We aren't using spi_write_then_read() because we need to be able
> +	 * to get hold of the effective_speed_hz from the xfer
> +	 */
> +	ret = spi_sync(priv->spi, &msg);

There is a handy wrapper, spi_sync_transfer() which will reduce boilerplate a
little and still let you get to the xfer.

> +	if (ret) {
> +		dev_err_ratelimited(&priv->spi->dev, "SPI transfer failed %pe\n",
> +				    ERR_PTR(ret));
> +		return ret;
> +	}
> +
> +	if (effective_speed_hz)
> +		*effective_speed_hz = xfer.effective_speed_hz;
> +
> +	return tsc2046_adc_get_value(priv->rx_one);
> +}
> +
> +static size_t tsc2046_adc_group_set_layout(struct tsc2046_adc_priv *priv,
> +					   unsigned int group,
> +					   unsigned int ch_idx)
> +{
> +	struct tsc2046_adc_ch_cfg *ch = &priv->ch_cfg[ch_idx];
> +	struct tsc2046_adc_group_layout *cur;
> +	unsigned int max_count, count_skip;
> +	unsigned int offset = 0;
> +
> +	if (group)
> +		offset = priv->l[group - 1].offset + priv->l[group - 1].count;
> +
> +	count_skip = tsc2046_adc_time_to_count(priv, ch->settling_time_us);
> +	max_count = count_skip + ch->oversampling_ratio;
> +
> +	cur = &priv->l[group];
> +	cur->offset = offset;
> +	cur->count = max_count;
> +	cur->skip = count_skip;
> +
> +	return sizeof(*priv->tx) * max_count;
> +}
> +
> +static void tsc2046_adc_group_set_cmd(struct tsc2046_adc_priv *priv,
> +				      unsigned int group, int ch_idx)
> +{
> +	struct tsc2046_adc_group_layout *l = &priv->l[group];
> +	unsigned int i;
> +	u8 cmd;
> +
> +	/*
> +	 * Do not enable automatic power down on working samples. Otherwise the
> +	 * plates will never be completely charged.
> +	 */
> +	cmd = tsc2046_adc_get_cmd(priv, ch_idx, true);
> +
> +	for (i = 0; i < l->count - 1; i++)
> +		priv->tx[l->offset + i].cmd = cmd;
> +
> +	/* automatically power down on last sample */
> +	priv->tx[l->offset + i].cmd = tsc2046_adc_get_cmd(priv, ch_idx, false);
> +}
> +
> +static u16 tsc2046_adc_get_val(struct tsc2046_adc_priv *priv, int group)
> +{
> +	struct tsc2046_adc_group_layout *l;
> +	unsigned int val, val_normalized = 0;
> +	int valid_count, i;
> +
> +	l = &priv->l[group];
> +	valid_count = l->count - l->skip;
> +
> +	for (i = 0; i < valid_count; i++) {
> +		val = tsc2046_adc_get_value(&priv->rx[l->offset + l->skip + i]);
> +		val_normalized += val;
> +	}
> +
> +	return DIV_ROUND_UP(val_normalized, valid_count);
> +}
> +
> +static int tsc2046_adc_scan(struct iio_dev *indio_dev)
> +{
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +	struct device *dev = &priv->spi->dev;
> +	int group;
> +	int ret;
> +
> +	ret = spi_sync(priv->spi, &priv->msg);
> +	if (ret < 0) {
> +		dev_err_ratelimited(dev, "SPI transfer failed: %pe\n", ERR_PTR(ret));
> +		return ret;
> +	}
> +
> +	for (group = 0; group < priv->groups; group++)
> +		priv->scan_buf.data[group] = tsc2046_adc_get_val(priv, group);
> +
> +	ret = iio_push_to_buffers_with_timestamp(indio_dev, &priv->scan_buf,
> +						 iio_get_time_ns(indio_dev));
> +	/* If the consumer is kfifo, we may get a EBUSY here - ignore it. */
> +	if (ret < 0 && ret != -EBUSY) {
> +		dev_err_ratelimited(dev, "Failed to push scan buffer %pe\n",
> +				    ERR_PTR(ret));
> +
> +		return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static irqreturn_t tsc2046_adc_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +
> +	mutex_lock(&priv->slock);
> +	tsc2046_adc_scan(indio_dev);
> +	mutex_unlock(&priv->slock);
> +
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static int tsc2046_adc_update_scan_mode(struct iio_dev *indio_dev,
> +					const unsigned long *active_scan_mask)
> +{
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +	unsigned int ch_idx, group = 0;
> +	size_t size;
> +
> +	mutex_lock(&priv->slock);
> +
> +	size = 0;
> +	for_each_set_bit(ch_idx, active_scan_mask, indio_dev->num_channels) {
> +		size += tsc2046_adc_group_set_layout(priv, group, ch_idx);
> +		tsc2046_adc_group_set_cmd(priv, group, ch_idx);
> +		group++;
> +	}
> +
> +	priv->groups = group;
> +	priv->xfer.len = size;
> +	priv->time_per_scan_us = size * 8 * priv->time_per_bit_ns / NSEC_PER_USEC;
> +
> +	if ((priv->scan_interval_us - priv->time_per_scan_us) < 0)
> +		dev_warn(&priv->spi->dev, "The scan interval (%d) is less then calculated scan time (%d)\n",
> +			 priv->scan_interval_us, priv->time_per_scan_us);
> +
> +	mutex_unlock(&priv->slock);
> +
> +	return 0;
> +}
> +
> +static const struct iio_info tsc2046_adc_info = {
> +	.update_scan_mode = tsc2046_adc_update_scan_mode,
> +};
> +
> +static enum hrtimer_restart tsc2046_adc_trig_more(struct hrtimer *hrtimer)
> +{
> +	struct tsc2046_adc_priv *priv = container_of(hrtimer,
> +						     struct tsc2046_adc_priv,
> +						     trig_timer);
> +	unsigned long flags;
> +
> +	spin_lock_irqsave(&priv->trig_lock, flags);
> +
> +	disable_irq_nosync(priv->spi->irq);
> +
> +	priv->trig_more_count++;
> +	iio_trigger_poll(priv->trig);
> +
> +	spin_unlock_irqrestore(&priv->trig_lock, flags);
> +
> +	return HRTIMER_NORESTART;
> +}
> +
> +static irqreturn_t tsc2046_adc_irq(int irq, void *dev_id)
> +{
> +	struct iio_dev *indio_dev = dev_id;
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +
> +	spin_lock(&priv->trig_lock);
> +
> +	hrtimer_try_to_cancel(&priv->trig_timer);
> +
> +	priv->trig_more_count = 0;
> +	disable_irq_nosync(priv->spi->irq);
> +	iio_trigger_poll(priv->trig);
> +
> +	spin_unlock(&priv->trig_lock);
> +
> +	return IRQ_HANDLED;
> +}
> +
> +static void tsc2046_adc_reenable_trigger(struct iio_trigger *trig)
> +{
> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +	unsigned long flags;
> +	int delta;
> +
> +	/*
> +	 * We can sample it as fast as we can, but usually we do not need so
> +	 * many samples. Reduce the sample rate for default (touchscreen) use
> +	 * case.
> +	 * Currently we do not need a highly precise sample rate. It is enough
> +	 * to have calculated numbers.
> +	 */
> +	delta = priv->scan_interval_us - priv->time_per_scan_us;
> +	if (delta > 0)
> +		fsleep(delta);
> +
> +	spin_lock_irqsave(&priv->trig_lock, flags);
> +
> +	/*
> +	 * We need to trigger at least one extra sample to detect state
> +	 * difference on ADC side.
> +	 */
> +	if (!priv->trig_more_count) {
> +		int timeout_ms = DIV_ROUND_UP(priv->scan_interval_us,
> +					      USEC_PER_MSEC);
> +
> +		hrtimer_start(&priv->trig_timer, ms_to_ktime(timeout_ms),
> +			      HRTIMER_MODE_REL_SOFT);
> +	}
> +
> +	enable_irq(priv->spi->irq);
> +
> +	spin_unlock_irqrestore(&priv->trig_lock, flags);
> +}
> +
> +static int tsc2046_adc_set_trigger_state(struct iio_trigger *trig, bool enable)
> +{
> +	struct iio_dev *indio_dev = iio_trigger_get_drvdata(trig);
> +	struct tsc2046_adc_priv *priv = iio_priv(indio_dev);
> +
> +	if (enable) {
> +		enable_irq(priv->spi->irq);
> +	} else {
> +		disable_irq(priv->spi->irq);
> +		hrtimer_try_to_cancel(&priv->trig_timer);
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct iio_trigger_ops tsc2046_adc_trigger_ops = {
> +	.set_trigger_state = tsc2046_adc_set_trigger_state,
> +	.reenable = tsc2046_adc_reenable_trigger,
> +};
> +
> +static int tsc2046_adc_setup_spi_msg(struct tsc2046_adc_priv *priv)
> +{
> +	unsigned int ch_idx;
> +	size_t size;
> +	int ret;
> +
> +	priv->tx_one = devm_kzalloc(&priv->spi->dev, sizeof(*priv->tx_one),
> +				    GFP_KERNEL);
> +	if (!priv->tx_one)
> +		return -ENOMEM;
> +
> +	priv->rx_one = devm_kzalloc(&priv->spi->dev, sizeof(*priv->rx_one),
> +				    GFP_KERNEL);
> +	if (!priv->rx_one)
> +		return -ENOMEM;
> +
> +	/*
> +	 * Make dummy read to set initial power state and get real SPI clock
> +	 * freq. It seems to be not important which channel is used for this
> +	 * case.
> +	 */
> +	ret = tsc2046_adc_read_one(priv, TI_TSC2046_ADDR_TEMP0,
> +				   &priv->effective_speed_hz);
> +	if (ret < 0)
> +		return ret;
> +
> +	/*
> +	 * In case SPI controller do not report effective_speed_hz, use
> +	 * configure value and hope it will match.
> +	 */
> +	if (!priv->effective_speed_hz)
> +		priv->effective_speed_hz = priv->spi->max_speed_hz;
> +
> +
> +	priv->scan_interval_us = TI_TSC2046_SAMPLE_INTERVAL_US;
> +	priv->time_per_bit_ns = DIV_ROUND_UP(NSEC_PER_SEC,
> +					     priv->effective_speed_hz);
> +
> +	/*
> +	 * Calculate and allocate maximal size buffer if all channels are
> +	 * enabled.
> +	 */
> +	size = 0;
> +	for (ch_idx = 0; ch_idx < priv->dcfg->num_channels; ch_idx++)
> +		size += tsc2046_adc_group_set_layout(priv, ch_idx, ch_idx);
> +
> +	priv->tx = devm_kzalloc(&priv->spi->dev, size, GFP_KERNEL);
> +	if (!priv->tx)
> +		return -ENOMEM;
> +
> +	priv->rx = devm_kzalloc(&priv->spi->dev, size, GFP_KERNEL);
> +	if (!priv->rx)
> +		return -ENOMEM;
> +
> +	spi_message_init(&priv->msg);
> +	priv->msg.context = priv;
> +
> +	priv->xfer.tx_buf = priv->tx;
> +	priv->xfer.rx_buf = priv->rx;
> +	priv->xfer.len = size;
> +	spi_message_add_tail(&priv->xfer, &priv->msg);
> +
> +	return 0;
> +}
> +
> +static void tsc2046_adc_parse_fwnode(struct tsc2046_adc_priv *priv)
> +{
> +	struct fwnode_handle *child;
> +	struct device *dev = &priv->spi->dev;
> +	unsigned int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(priv->ch_cfg); i++) {
> +		priv->ch_cfg[i].settling_time_us = 1;
> +		priv->ch_cfg[i].oversampling_ratio = 1;
> +	}
> +
> +	device_for_each_child_node(dev, child) {
> +		u32 stl, overs, reg;
> +		int ret;
> +
> +		ret = fwnode_property_read_u32(child, "reg", &reg);
> +		if (ret) {
> +			dev_err(dev, "invalid reg on %pfw, err: %pe\n", child,
> +				ERR_PTR(ret));
> +			continue;
> +		}
> +
> +		if (reg >= ARRAY_SIZE(priv->ch_cfg)) {
> +			dev_err(dev, "%pfw: Unsupported reg value: %i, max supported is: %zu.\n",
> +				child, reg, ARRAY_SIZE(priv->ch_cfg));
> +			continue;
> +		}
> +
> +		ret = fwnode_property_read_u32(child, "settling-time-us", &stl);

I should have picked up on this before.  We should ideally distinguish between
the property not being present (in which case we carry on) and the read of a
present property failing. Also good to sanity check range etc here and return
an error if they are invalid.

		if (device_property_present(child, "settling-time-us")) {
			ret = fw_node_property_read_u32(...)
			if (ret)
				return ret;
		}

You can do it by checking the error value of fw_node_property_read_u32, but that
ends up looking more messy and harder to follow.


> +		if (!ret)
> +			priv->ch_cfg[reg].settling_time_us = stl;
> +
> +		ret = fwnode_property_read_u32(child, "oversampling-ratio",
> +					       &overs);

As per review on patch 1, this is the main remaining question I have.
Why is oversampling ratio controlled from DT?

> +		if (!ret)
> +			priv->ch_cfg[reg].oversampling_ratio = overs;
> +	}
> +}
> +
> +static int tsc2046_adc_probe(struct spi_device *spi)
> +{
> +	const struct tsc2046_adc_dcfg *dcfg;
> +	struct device *dev = &spi->dev;
> +	struct tsc2046_adc_priv *priv;
> +	struct iio_dev *indio_dev;
> +	struct iio_trigger *trig;
> +	const char *name;
> +	int ret;
> +
> +	if (spi->max_speed_hz > TI_TSC2046_MAX_CLK_FREQ) {
> +		dev_err(dev, "SPI max_speed_hz is too high: %d Hz. Max supported freq is %zu Hz\n",
> +			spi->max_speed_hz, TI_TSC2046_MAX_CLK_FREQ);
> +		return -EINVAL;
> +	}
> +
> +	dcfg = device_get_match_data(dev);
> +	if (!dcfg)
> +		return -EINVAL;
> +
> +	spi->bits_per_word = 8;
> +	spi->mode &= ~SPI_MODE_X_MASK;
> +	spi->mode |= SPI_MODE_0;
> +	ret = spi_setup(spi);
> +	if (ret < 0)
> +		return dev_err_probe(dev, ret, "Error in SPI setup\n");
> +
> +	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
> +	if (!indio_dev)
> +		return -ENOMEM;
> +
> +	priv = iio_priv(indio_dev);
> +	priv->dcfg = dcfg;
> +
> +	spi_set_drvdata(spi, indio_dev);
> +
> +	priv->spi = spi;
> +
> +	name = devm_kasprintf(dev, GFP_KERNEL, "%s-%s",
> +			      TI_TSC2046_NAME, dev_name(dev));

I'd missed this before, what does this name end up as?

For IIO devices, that field is used for part number, not a hybrid
of that and the name of the spi device (which you can get trivially
from the appropriate directory links in sysfs).
If we do need a more complex name (usually describing something like
location within the device if there are systems with multiple identical
parts) then we have the label attribute for that.


> +	if (!name)
> +		return -ENOMEM;
> +
> +	indio_dev->name = name;
> +	indio_dev->modes = INDIO_DIRECT_MODE | INDIO_BUFFER_TRIGGERED;
> +	indio_dev->channels = dcfg->channels;
> +	indio_dev->num_channels = dcfg->num_channels;
> +	indio_dev->info = &tsc2046_adc_info;
> +
> +	tsc2046_adc_parse_fwnode(priv);
> +
> +	ret = tsc2046_adc_setup_spi_msg(priv);
> +	if (ret)
> +		return ret;
> +
> +	mutex_init(&priv->slock);
> +
> +	/* TODO: remove IRQ_NOAUTOEN after needed patches are mainline */

For this, I'm happy to merge in the immutable branch that exists for
that patch (it's already gone in via at least 2 trees)

https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/log/?h=irq-no-autoen-2021-03-25

So if you want to do it directly, just note that dependency in the cover letter.

I'll shortly be doing a sweep of IIO to clean up all the other instances of
this and hence pulling that patch in anyway.

> +	irq_set_status_flags(spi->irq, IRQ_NOAUTOEN);
> +	ret = devm_request_irq(dev, spi->irq, &tsc2046_adc_irq,
> +			       0, name, indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	trig = devm_iio_trigger_alloc(dev, "touchscreen-%s", indio_dev->name);
> +	if (!trig)
> +		return -ENOMEM;
> +
> +	priv->trig = trig;
> +	iio_trigger_set_drvdata(trig, indio_dev);
> +	trig->ops = &tsc2046_adc_trigger_ops;
> +
> +	spin_lock_init(&priv->trig_lock);
> +	hrtimer_init(&priv->trig_timer, CLOCK_MONOTONIC,
> +		     HRTIMER_MODE_REL_SOFT);
> +	priv->trig_timer.function = tsc2046_adc_trig_more;
> +
> +	ret = devm_iio_trigger_register(dev, trig);
> +	if (ret) {
> +		dev_err(dev, "failed to register trigger\n");
> +		return ret;
> +	}
> +
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
> +					      &tsc2046_adc_trigger_handler, NULL);
> +	if (ret) {
> +		dev_err(dev, "Failed to setup triggered buffer\n");
> +		return ret;
> +	}
> +
> +	/* set default trigger */
> +	indio_dev->trig = iio_trigger_get(priv->trig);
> +
> +	return devm_iio_device_register(dev, indio_dev);
> +}
> +
> +static const struct of_device_id ads7950_of_table[] = {
> +	{ .compatible = "ti,tsc2046e-adc", .data = &tsc2046_adc_dcfg_tsc2046e },
> +	{ }
> +};
> +MODULE_DEVICE_TABLE(of, ads7950_of_table);
> +
> +static struct spi_driver tsc2046_adc_driver = {
> +	.driver = {
> +		.name = "tsc2046",
> +		.of_match_table = ads7950_of_table,
> +	},
> +	.probe = tsc2046_adc_probe,
> +};
> +module_spi_driver(tsc2046_adc_driver);
> +
> +MODULE_AUTHOR("Oleksij Rempel <kernel@...gutronix.de>");
> +MODULE_DESCRIPTION("TI TSC2046 ADC");
> +MODULE_LICENSE("GPL v2");

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