Date:   Tue, 16 Mar 2021 06:57:14 +0100
From:   Oleksij Rempel <o.rempel@...gutronix.de>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     devicetree@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org,
        Robin van der Gracht <robin@...tonic.nl>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        David Jander <david@...tonic.nl>
Subject: Re: [PATCH v2 3/3] iio: adc: add ADC driver for the TI TSC2046
 controller

Hi,

On Sat, Mar 13, 2021 at 04:11:19PM +0000, Jonathan Cameron wrote:
> On Fri, 12 Mar 2021 11:55:15 +0100
> 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 IIO ADC device, we can
> > make use of resistive-adc-touch and iio-hwmon drivers.
> > 
> > So far, this driver was tested with custom version of resistive-adc-touch driver,
> > since it need 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>
> 
> So the flow in here is still rather non obvious and touchscreen specific.
> Please add some documentation on what the trigger actually is. It seems
> to be some combination of an hrtimer and a interrupt driven trigger.
> I 'think' the idea is to ensure you get one 'no touch' measurement once
> touch is removed?


Yes, this IRQ line is just a voltage level converter integrated in to
controller. As soon voltage level reaches some threshold the IRQ level
is changed. It means, the IRQ is inactive as soon as nothing is pressing
on the screen, or the channel is changed. Since we need more sample and not so
frequent, I made this construction of rate limited IRQ with extra triggering on
the end.

Potentially we can use hrtimer trigger, especially if the IRQ line
is not attached or can't be used for some reason. But for most use cases
this trigger will provide better power efficiency.

I can imagine, that in case of field board diagnostic, we may need some extra
functionality. So the workflow will look like:
- unbind the touchscreen driver
- disable oversampling
- disable settling time
- attach sysfs trigger
- enable one of channels
- start grabbing data over IIO char dev

But this functionality will need some more work and currently has lowest
prio.

> I guess we don't need the performance but I was a bit surprised that I didn't
> see this doing overlapping of the previous read out with the config for the
> next sample.

I can't follow here. Can you please explain.

> Anyhow, overall this looks pretty good to me.  Add that a bit of documentation
> for the trigger to the comments at the top of the file and tidy up the last
> few things inline.

ok

> It's a bit unusual as ADC drivers go, but not so strange that it worries
> me that much.

:)

> Thanks,
> 
> Jonathan
> 
> > ---
> >  MAINTAINERS                  |   8 +
> >  drivers/iio/adc/Kconfig      |  12 +
> >  drivers/iio/adc/Makefile     |   1 +
> >  drivers/iio/adc/ti-tsc2046.c | 713 +++++++++++++++++++++++++++++++++++
> >  4 files changed, 734 insertions(+)
> >  create mode 100644 drivers/iio/adc/ti-tsc2046.c
> > 
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index 3fea1a934b32..2d33c6442a55 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -17852,6 +17852,14 @@ 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 15587a1bc80d..6ad6f04dfd20 100644
> > --- a/drivers/iio/adc/Kconfig
> > +++ b/drivers/iio/adc/Kconfig
> > @@ -1175,6 +1175,18 @@ 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 5fca90ada0ec..440e18ac6780 100644
> > --- a/drivers/iio/adc/Makefile
> > +++ b/drivers/iio/adc/Makefile
> > @@ -105,6 +105,7 @@ obj-$(CONFIG_TI_ADS8688) += ti-ads8688.o
> >  obj-$(CONFIG_TI_ADS124S08) += ti-ads124s08.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..7c3ae9181164
> > --- /dev/null
> > +++ b/drivers/iio/adc/ti-tsc2046.c
> > @@ -0,0 +1,713 @@
> > +// 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>
> > +
> > +#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			(8 /*cmd*/ + 16 /*sample*/)
> > +#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)
> > +
> > +#define TI_TSC2046_MAX_CHAN			8
> > +
> > +/* Represents a HW sample */
> > +struct tsc2046_adc_atom {
> > +	/*
> > +	 * Command transmitted to the controller. This filed is empty on the RX
> > +	 * buffer.
> > +	 */
> > +	u8 cmd;
> > +	/*
> > +	 * Data received from the controller. This filed is empty for the TX
> > +	 * buffer
> > +	 */
> > +	__be16 data;
> > +} __packed;
> > +
> > +struct tsc2046_adc_scan_buf {
> > +	/* Scan data for each channel */
> > +	u16 data[TI_TSC2046_MAX_CHAN];
> > +	/* Timestamp */
> > +	s64 ts __aligned(8);
> > +};
> > +
> > +/* 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 average_samples;
> > +};
> > +
> > +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;
> > +	atomic_t trig_more_count;
> > +
> > +	struct spi_transfer xfer;
> > +	struct spi_message msg;
> > +
> > +	struct tsc2046_adc_scan_buf 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,					\
> > +	.address = index,					\
> 
> Don't think you ever use address, so don't set it.
> 
> > +	.datasheet_name = "#name",				\
> > +	.scan_index = index,					\
> > +	.scan_type = {						\
> > +		.sign = 'u',					\
> > +		.realbits = bits,				\
> > +		.storagebits = 16,				\
> > +		.shift = 0,					\
> 
> Shift of 0 assumed default, so no need to specify that here (it'll end
> up 0 anyway)
> 
> > +		.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)
> > +{
> > +	/* Last 3 bits on the wire are empty */
> > +	return get_unaligned_be16(&buf->data) >> 3;
> > +}
> > +
> > +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);
> 
> Perhaps add a comment that you aren't using spi_write_then_read() because
> you need to be able to get hold of the effective_speed_hz from the
> xfer.
> 
> > +
> > +	ret = spi_sync(priv->spi, &msg);
> > +	if (ret) {
> > +		dev_err_ratelimited(&priv->spi->dev, "SPI transfer filed %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 *prev, *cur;
> > +	unsigned int max_count, count_skip;
> > +	unsigned int offset = 0;
> > +
> 
> One blank line almost always enough :)
> 
> > +
> > +	if (group) {
> > +		prev = &priv->l[group - 1];
> > +		offset = prev->offset + prev->count;
> > +	}
> > +
> > +	cur = &priv->l[group];
> > +
> > +	count_skip = tsc2046_adc_time_to_count(priv, ch->settling_time_us);
> > +	max_count = count_skip + ch->average_samples;
> > +
> > +	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 filed: %pe\n",
> > +				    ERR_PTR(ret));
> > +		return ret;
> > +	}
> > +
> > +	for (group = 0; group < priv->groups; group++) {
> > +		u16 val = tsc2046_adc_get_val(priv, group);
> > +
> > +		priv->scan_buf.data[group] = val;
> 
> nitpick, but why not the more compact:
> 		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 there's no consumer (or consumer is kfifo), may get a EBUSY here
> > +	 * - ignore it.
> 
> The no consumer case should be impossible (I hope!), but fair enough of kfifo side of
> things.
> 
> > +	 */
> > +	if (ret < 0 && ret != -EBUSY) {
> > +		dev_err_ratelimited(dev, "Filed to push scan buffer %pe\n",
> > +				    ERR_PTR(ret));
> 
> Failed
> 
> > +
> > +		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 = 0;
> > +
> > +	mutex_lock(&priv->slock);
> > +
> > +	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);
> > +
> > +	atomic_inc(&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);
> > +
> 
> One blank line is enough.
> 
> > +
> > +	spin_lock(&priv->trig_lock);
> > +
> > +	hrtimer_try_to_cancel(&priv->trig_timer);
> > +
> > +	atomic_set(&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 (atomic_read(&priv->trig_more_count) == 0) {
> > +		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 = 0;
> > +	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.
> > +	 */
> > +	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;
> > +
> > +	device_for_each_child_node(dev, child) {
> > +		u32 stl, aver, 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: %i.\n",
> > +				child, reg, ARRAY_SIZE(priv->ch_cfg));
> > +			continue;
> > +		}
> > +
> > +		ret = fwnode_property_read_u32(child, "settling-time-us", &stl);
> > +		if (!ret)
> > +			priv->ch_cfg[reg].settling_time_us = stl;
> > +
> > +		ret = fwnode_property_read_u32(child, "average-samples", &aver);
> > +		if (!ret)
> > +			priv->ch_cfg[reg].average_samples = aver;
> > +	}
> > +}
> > +
> > +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 %d 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));
> > +
> > +	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 */
> > +	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, "%s-dev%d", indio_dev->name,
> > +				      indio_dev->id);
> 
> Given the trigger a more descriptive name to reflect that it is 'touch'
> based.
> 
> > +	if (!trig)
> > +		return -ENOMEM;
> > +
> > +	priv->trig = trig;
> > +	trig->dev.parent = indio_dev->dev.parent;
> > +	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);
> > +
> > +	ret = devm_iio_device_register(dev, indio_dev);
> > +	if (ret) {
> > +		dev_err(dev, "Failed to register iio device\n");
> > +		return ret;
> > +	}
> > +
> > +	return 0;
> > +}
> > +
> > +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");
> 
> 
> 

-- 
Pengutronix e.K.                           |                             |
Steuerwalder Str. 21                       | http://www.pengutronix.de/  |
31137 Hildesheim, Germany                  | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

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