[PATCH 0/5] iio: adc: ad_sigma_delta: Add sequencer support

[PATCH 0/5] iio: adc: ad_sigma_delta: Add sequencer support

[alexandru.tachici]

From: Alexandru Tachici <alexandru.tachici@analog.com>

Some sigma-delta chips support sampling of multiple
channels in continuous mode.

When the operating with more than one channel enabled,
the channel sequencer cycles through the enabled channels
in sequential order, from first channel to the last one.
If a channel is disabled, it is skipped by the sequencer.

If more than one channel is used in continuous mode,
instruct the device to append the status to the SPI transfer
(1 extra byte) every time we receive a sample.
All sigma-delta chips possessing a sampling sequencer have
this ability. Inside the status register there will be
the number of the converted channel. In this way, even
if the CPU won't keep up with the sampling rate, it won't
send to userspace wrong channel samples.

1. Fix bug in AD7124 where channels stayed enabled
even when they are not supposed to, in continuous mode.

2. Fix bug in AD7192 where channels stayed enabled
even when they are not supposed to, in continuous mode.

3. Add sequencer support for sigma_delta library.

4. Add sigma_delta_info values and callbacks for sequencer
support in AD7124.

5. Add sigma_delta_info values and callbacks for sequencer
support in AD7192.

Alexandru Tachici (5):
  iio: adc: ad7124: Add update_scan_mode
  iio: adc: ad7192: Add update_scan_mode
  iio: adc: ad_sigma_delta: Add sequencer support
  iio: adc: ad7124: add sequencer support
  iio: adc: ad7192: add sequencer support

 drivers/iio/adc/ad7124.c               |  38 ++++++++-
 drivers/iio/adc/ad7192.c               |  32 +++++++-
 drivers/iio/adc/ad_sigma_delta.c       | 106 ++++++++++++++++++++-----
 include/linux/iio/adc/ad_sigma_delta.h |  22 +++++
 4 files changed, 178 insertions(+), 20 deletions(-)

--
2.25.1

[PATCH 1/5] iio: adc: ad7124: Add update_scan_mode

[alexandru.tachici]

From: Alexandru Tachici <alexandru.tachici@analog.com>

In continuous mode neither sigma_delta.c nor ad7124.c
will disable previously enabled channels.

Before this patch a channel stayed enabled indefinetly,
even when one another one was supposed to be sampled.
This causes mixed samples in continuous mode to be delivered
to the host.

By adding an update_scan_mode callback, every time the
continuous mode is activated, channels will be enabled/disabled
accordingly.

Fixes: b3af341bbd966 ("iio: adc: Add ad7124 support")
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
---
 drivers/iio/adc/ad7124.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 11ce6a3729a5..30299b899799 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -669,11 +669,32 @@ static const struct attribute_group ad7124_attrs_group = {
 	.attrs = ad7124_attributes,
 };
 
+static int ad7124_update_scan_mode(struct iio_dev *indio_dev,
+				   const unsigned long *scan_mask)
+{
+	struct ad7124_state *st = iio_priv(indio_dev);
+	bool bit_set;
+	int ret;
+	int i;
+
+	for (i = 0; i < st->num_channels; i++) {
+		bit_set = test_bit(i, scan_mask);
+		ret = ad7124_spi_write_mask(st, AD7124_CHANNEL(i),
+					    AD7124_CHANNEL_EN_MSK,
+					    AD7124_CHANNEL_EN(bit_set),
+					    2);
+		if (ret < 0)
+			return ret;
+	}
+	return 0;
+}
+
 static const struct iio_info ad7124_info = {
 	.read_raw = ad7124_read_raw,
 	.write_raw = ad7124_write_raw,
 	.debugfs_reg_access = &ad7124_reg_access,
 	.validate_trigger = ad_sd_validate_trigger,
+	.update_scan_mode = ad7124_update_scan_mode,
 	.attrs = &ad7124_attrs_group,
 };
 
-- 
2.25.1

Re: [PATCH 1/5] iio: adc: ad7124: Add update_scan_mode

[Jonathan Cameron]

On Wed, 10 Nov 2021 13:17:46 +0200
<alexandru.tachici@analog.com> wrote:

> From: Alexandru Tachici <alexandru.tachici@analog.com>
> 
> In continuous mode neither sigma_delta.c nor ad7124.c
> will disable previously enabled channels.
> 
> Before this patch a channel stayed enabled indefinetly,
> even when one another one was supposed to be sampled.
> This causes mixed samples in continuous mode to be delivered
> to the host.
> 
> By adding an update_scan_mode callback, every time the
> continuous mode is activated, channels will be enabled/disabled
> accordingly.
> 
> Fixes: b3af341bbd966 ("iio: adc: Add ad7124 support")
> Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>

I'm a little confused about which paths this bug affects.

If we have done a single channel read, then the channel is always
disabled afterwards so we won't leave one on in that path.

So the remaining path is on a previous buffer setup. In that path
set_channel is called as part the post_enable callback and will
enable the channel.

Currently nothing disables it again, so I guess if you then
change the enabled channels and restart the buffer you see the
condition you are covering here.

However, as I read the docs, this should also affect any
single reads of a later channel than the one that was originally enabled.
e.g. buffered capture enabled for channel 0 then disabled.  Later read of
channel 1 may get the data from channel 0.

The fix you have here won't close that path because we don't
call update_scan_mode() in the buffer disable path (we have considered
it a few times, but so many devices don't have to do an explicit disable there
that we never put it in). Perhaps with hindsight we should have always
called it in the disable path, but maybe with a parameter to allow devices
to opt out of doing anything.

We could add core callback called something like disable_all() which
is called in the remove path. Alternatively the issue can be closed
in the ad_sigma_delta core by adding a callback to disable channels
in predisable().

Jonathan
 

> ---
>  drivers/iio/adc/ad7124.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
> index 11ce6a3729a5..30299b899799 100644
> --- a/drivers/iio/adc/ad7124.c
> +++ b/drivers/iio/adc/ad7124.c
> @@ -669,11 +669,32 @@ static const struct attribute_group ad7124_attrs_group = {
>  	.attrs = ad7124_attributes,
>  };
>  
> +static int ad7124_update_scan_mode(struct iio_dev *indio_dev,
> +				   const unsigned long *scan_mask)
> +{
> +	struct ad7124_state *st = iio_priv(indio_dev);
> +	bool bit_set;
> +	int ret;
> +	int i;
> +
> +	for (i = 0; i < st->num_channels; i++) {
> +		bit_set = test_bit(i, scan_mask);
> +		ret = ad7124_spi_write_mask(st, AD7124_CHANNEL(i),
> +					    AD7124_CHANNEL_EN_MSK,
> +					    AD7124_CHANNEL_EN(bit_set),
> +					    2);
> +		if (ret < 0)
> +			return ret;
> +	}
> +	return 0;
> +}
> +
>  static const struct iio_info ad7124_info = {
>  	.read_raw = ad7124_read_raw,
>  	.write_raw = ad7124_write_raw,
>  	.debugfs_reg_access = &ad7124_reg_access,
>  	.validate_trigger = ad_sd_validate_trigger,
> +	.update_scan_mode = ad7124_update_scan_mode,
>  	.attrs = &ad7124_attrs_group,
>  };
>  

[PATCH 2/5] iio: adc: ad7192: Add update_scan_mode

[alexandru.tachici]

From: Alexandru Tachici <alexandru.tachici@analog.com>

In continuous mode neither sigma_delta.c nor ad7192.c
will disable previously enabled channels.

Before this patch a channel stayed enabled indefinetly,
even when one another one was supposed to be sampled.
This causes mixed samples in continuous mode to be delivered
to the host.

By adding an update_scan_mode callback, every time the
continuous mode is activated, channels will be enabled/disabled
accordingly.

Fixes: 3f7c3306cf38 ("staging:iio:ad7192: Use common Sigma Delta library")
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
---
 drivers/iio/adc/ad7192.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
index 2121a812b0c3..1fc0f4eb858e 100644
--- a/drivers/iio/adc/ad7192.c
+++ b/drivers/iio/adc/ad7192.c
@@ -782,6 +782,20 @@ static int ad7192_read_avail(struct iio_dev *indio_dev,
 	return -EINVAL;
 }
 
+static int ad7192_update_scan_mode(struct iio_dev *indio_dev, const unsigned long *scan_mask)
+{
+	struct ad7192_state *st = iio_priv(indio_dev);
+	int i;
+
+	st->conf &= ~AD7192_CONF_CHAN_MASK;
+	for (i = 0; i < 8; i++) {
+		if (test_bit(i, scan_mask))
+			st->conf |= AD7192_CONF_CHAN(i);
+	}
+
+	return ad_sd_write_reg(&st->sd, AD7192_REG_CONF, 3, st->conf);
+}
+
 static const struct iio_info ad7192_info = {
 	.read_raw = ad7192_read_raw,
 	.write_raw = ad7192_write_raw,
@@ -789,6 +803,7 @@ static const struct iio_info ad7192_info = {
 	.read_avail = ad7192_read_avail,
 	.attrs = &ad7192_attribute_group,
 	.validate_trigger = ad_sd_validate_trigger,
+	.update_scan_mode = ad7192_update_scan_mode,
 };
 
 static const struct iio_info ad7195_info = {
@@ -798,6 +813,7 @@ static const struct iio_info ad7195_info = {
 	.read_avail = ad7192_read_avail,
 	.attrs = &ad7195_attribute_group,
 	.validate_trigger = ad_sd_validate_trigger,
+	.update_scan_mode = ad7192_update_scan_mode,
 };
 
 #define __AD719x_CHANNEL(_si, _channel1, _channel2, _address, _extend_name, \
-- 
2.25.1

Re: [PATCH 2/5] iio: adc: ad7192: Add update_scan_mode

[Jonathan Cameron]

On Wed, 10 Nov 2021 13:17:47 +0200
<alexandru.tachici@analog.com> wrote:

> From: Alexandru Tachici <alexandru.tachici@analog.com>
> 
> In continuous mode neither sigma_delta.c nor ad7192.c
> will disable previously enabled channels.
> 
> Before this patch a channel stayed enabled indefinetly,
> even when one another one was supposed to be sampled.
> This causes mixed samples in continuous mode to be delivered
> to the host.

Can you expand a bit on the path that leads to this.  As far as I can tell
in both continuous mode enable and single channel reading set_channel()
callback is called and will overwrite the channels enabled previously.

Perhaps I'm missing a path in which that call isn't made?
> 
> By adding an update_scan_mode callback, every time the
> continuous mode is activated, channels will be enabled/disabled
> accordingly.
> 
> Fixes: 3f7c3306cf38 ("staging:iio:ad7192: Use common Sigma Delta library")
> Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
> ---
>  drivers/iio/adc/ad7192.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)
> 
> diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
> index 2121a812b0c3..1fc0f4eb858e 100644
> --- a/drivers/iio/adc/ad7192.c
> +++ b/drivers/iio/adc/ad7192.c
> @@ -782,6 +782,20 @@ static int ad7192_read_avail(struct iio_dev *indio_dev,
>  	return -EINVAL;
>  }
>  
> +static int ad7192_update_scan_mode(struct iio_dev *indio_dev, const unsigned long *scan_mask)
> +{
> +	struct ad7192_state *st = iio_priv(indio_dev);
> +	int i;
> +
> +	st->conf &= ~AD7192_CONF_CHAN_MASK;
> +	for (i = 0; i < 8; i++) {
> +		if (test_bit(i, scan_mask))

for_each_set_bit()

> +			st->conf |= AD7192_CONF_CHAN(i);
> +	}
> +
> +	return ad_sd_write_reg(&st->sd, AD7192_REG_CONF, 3, st->conf);
> +}
> +
>  static const struct iio_info ad7192_info = {
>  	.read_raw = ad7192_read_raw,
>  	.write_raw = ad7192_write_raw,
> @@ -789,6 +803,7 @@ static const struct iio_info ad7192_info = {
>  	.read_avail = ad7192_read_avail,
>  	.attrs = &ad7192_attribute_group,
>  	.validate_trigger = ad_sd_validate_trigger,
> +	.update_scan_mode = ad7192_update_scan_mode,
>  };
>  
>  static const struct iio_info ad7195_info = {
> @@ -798,6 +813,7 @@ static const struct iio_info ad7195_info = {
>  	.read_avail = ad7192_read_avail,
>  	.attrs = &ad7195_attribute_group,
>  	.validate_trigger = ad_sd_validate_trigger,
> +	.update_scan_mode = ad7192_update_scan_mode,
>  };
>  
>  #define __AD719x_CHANNEL(_si, _channel1, _channel2, _address, _extend_name, \

[PATCH 3/5] iio: adc: ad_sigma_delta: Add sequencer support

[alexandru.tachici]

From: Alexandru Tachici <alexandru.tachici@analog.com>

Some sigma-delta chips support sampling of multiple
channels in continuous mode.

When the operating with more than one channel enabled,
the channel sequencer cycles through the enabled channels
in sequential order, from first channel to the last one.
If a channel is disabled, it is skipped by the sequencer.

If more than one channel is used in continuous mode,
instruct the device to append the status to the SPI transfer
(1 extra byte) every time we receive a sample.
All sigma-delta chips possessing a sampling sequencer have
this ability. Inside the status register there will be
the number of the converted channel. In this way, even
if the CPU won't keep up with the sampling rate, it won't
send to userspace wrong channel samples.

Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
---
 drivers/iio/adc/ad_sigma_delta.c       | 106 ++++++++++++++++++++-----
 include/linux/iio/adc/ad_sigma_delta.h |  22 +++++
 2 files changed, 110 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
index 1d652d9b2f5c..d595e7972975 100644
--- a/drivers/iio/adc/ad_sigma_delta.c
+++ b/drivers/iio/adc/ad_sigma_delta.c
@@ -342,33 +342,48 @@ EXPORT_SYMBOL_GPL(ad_sigma_delta_single_conversion);
 static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
 {
 	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
-	unsigned int channel;
+	unsigned int i, slot;
 	int ret;
 
-	channel = find_first_bit(indio_dev->active_scan_mask,
-				 indio_dev->masklength);
-	ret = ad_sigma_delta_set_channel(sigma_delta,
-		indio_dev->channels[channel].address);
-	if (ret)
-		return ret;
+	slot = 0;
+	for_each_set_bit(i, indio_dev->active_scan_mask, indio_dev->masklength) {
+		sigma_delta->slots[slot] = indio_dev->channels[i].address;
+		ret = ad_sigma_delta_set_channel(sigma_delta, indio_dev->channels[i].address);
+		if (ret)
+			return ret;
+		slot++;
+	}
+
+	sigma_delta->active_slots = slot;
+	sigma_delta->current_slot = 0;
+
+	if (sigma_delta->active_slots > 1) {
+		ret = ad_sigma_delta_append_status(sigma_delta, true);
+		if (ret)
+			return ret;
+	}
+
+	kfree(sigma_delta->samples_buf);
+	sigma_delta->samples_buf = kzalloc(slot * indio_dev->channels[0].scan_type.storagebits,
+					   GFP_KERNEL);
+	if (!sigma_delta->samples_buf)
+		return -ENOMEM;
 
 	spi_bus_lock(sigma_delta->spi->master);
 	sigma_delta->bus_locked = true;
 	sigma_delta->keep_cs_asserted = true;
 
 	ret = ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_CONTINUOUS);
-	if (ret)
-		goto err_unlock;
+	if (ret) {
+		kfree(sigma_delta->samples_buf);
+		spi_bus_unlock(sigma_delta->spi->master);
+		return ret;
+	}
 
 	sigma_delta->irq_dis = false;
 	enable_irq(sigma_delta->spi->irq);
 
 	return 0;
-
-err_unlock:
-	spi_bus_unlock(sigma_delta->spi->master);
-
-	return ret;
 }
 
 static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev)
@@ -386,6 +401,9 @@ static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev)
 	sigma_delta->keep_cs_asserted = false;
 	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);
 
+	if (sigma_delta->status_appended)
+		ad_sigma_delta_append_status(sigma_delta, false);
+
 	sigma_delta->bus_locked = false;
 	return spi_bus_unlock(sigma_delta->spi->master);
 }
@@ -396,6 +414,10 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
 	uint8_t *data = sigma_delta->rx_buf;
+	unsigned int transfer_size;
+	unsigned int sample_size;
+	unsigned int sample_pos;
+	unsigned int status_pos;
 	unsigned int reg_size;
 	unsigned int data_reg;
 
@@ -408,20 +430,55 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	else
 		data_reg = AD_SD_REG_DATA;
 
+	/* Status word will be appended to the sample during transfer */
+	if (sigma_delta->status_appended)
+		transfer_size = reg_size + 1;
+	else
+		transfer_size = reg_size;
+
 	switch (reg_size) {
 	case 4:
 	case 2:
 	case 1:
-		ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size, &data[0]);
+		status_pos = reg_size;
+		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[0]);
 		break;
 	case 3:
+		status_pos = reg_size + 1;
 		/* We store 24 bit samples in a 32 bit word. Keep the upper
 		 * byte set to zero. */
-		ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size, &data[1]);
+		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[1]);
 		break;
 	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data, pf->timestamp);
+	if (sigma_delta->status_appended) {
+		u8 converted_channel;
+
+		converted_channel = data[status_pos] & sigma_delta->info->status_ch_mask;
+		if (converted_channel != sigma_delta->slots[sigma_delta->current_slot]) {
+			/* Desynq occurred during continuous sampling of multiple channels.
+			 * Drop this incomplete sample and start from first channel again.
+			 */
+
+			sigma_delta->current_slot = 0;
+			iio_trigger_notify_done(indio_dev->trig);
+			sigma_delta->irq_dis = false;
+			enable_irq(sigma_delta->spi->irq);
+
+			return IRQ_HANDLED;
+		}
+	}
+
+	sample_size = indio_dev->channels[0].scan_type.storagebits / 8;
+	sample_pos = sample_size * sigma_delta->current_slot;
+	memcpy(&sigma_delta->samples_buf[sample_pos], data, sample_size);
+	sigma_delta->current_slot++;
+
+	if (sigma_delta->current_slot == sigma_delta->active_slots) {
+		sigma_delta->current_slot = 0;
+		iio_push_to_buffers_with_timestamp(indio_dev, sigma_delta->samples_buf,
+						   pf->timestamp);
+	}
 
 	iio_trigger_notify_done(indio_dev->trig);
 	sigma_delta->irq_dis = false;
@@ -430,10 +487,17 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
 	return IRQ_HANDLED;
 }
 
+static bool ad_sd_validate_scan_mask(struct iio_dev *indio_dev, const unsigned long *mask)
+{
+	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
+
+	return bitmap_weight(mask, indio_dev->masklength) <= sigma_delta->info->num_slots;
+}
+
 static const struct iio_buffer_setup_ops ad_sd_buffer_setup_ops = {
 	.postenable = &ad_sd_buffer_postenable,
 	.postdisable = &ad_sd_buffer_postdisable,
-	.validate_scan_mask = &iio_validate_scan_mask_onehot,
+	.validate_scan_mask = &ad_sd_validate_scan_mask,
 };
 
 static irqreturn_t ad_sd_data_rdy_trig_poll(int irq, void *private)
@@ -517,8 +581,14 @@ static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_de
  */
 int devm_ad_sd_setup_buffer_and_trigger(struct device *dev, struct iio_dev *indio_dev)
 {
+	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
 	int ret;
 
+	sigma_delta->slots = devm_kcalloc(dev, sigma_delta->info->num_slots,
+					  sizeof(*sigma_delta->slots), GFP_KERNEL);
+	if (!sigma_delta->slots)
+		return -ENOMEM;
+
 	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
 					      &iio_pollfunc_store_time,
 					      &ad_sd_trigger_handler,
diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h
index c525fd51652f..758ff25590c3 100644
--- a/include/linux/iio/adc/ad_sigma_delta.h
+++ b/include/linux/iio/adc/ad_sigma_delta.h
@@ -32,6 +32,7 @@ struct iio_dev;
 /**
  * struct ad_sigma_delta_info - Sigma Delta driver specific callbacks and options
  * @set_channel: Will be called to select the current channel, may be NULL.
+ * @append_status: Will be called to enable status append at the end of the sample, may be NULL.
  * @set_mode: Will be called to select the current mode, may be NULL.
  * @postprocess_sample: Is called for each sampled data word, can be used to
  *		modify or drop the sample data, it, may be NULL.
@@ -39,19 +40,24 @@ struct iio_dev;
  *		if there is just one read-only sample data shift register.
  * @addr_shift: Shift of the register address in the communications register.
  * @read_mask: Mask for the communications register having the read bit set.
+ * @status_ch_mask: Mask for the channel number stored in status register.
  * @data_reg: Address of the data register, if 0 the default address of 0x3 will
  *   be used.
  * @irq_flags: flags for the interrupt used by the triggered buffer
+ * @num_slots: Number of sequencer slots
  */
 struct ad_sigma_delta_info {
 	int (*set_channel)(struct ad_sigma_delta *, unsigned int channel);
+	int (*append_status)(struct ad_sigma_delta *, bool append);
 	int (*set_mode)(struct ad_sigma_delta *, enum ad_sigma_delta_mode mode);
 	int (*postprocess_sample)(struct ad_sigma_delta *, unsigned int raw_sample);
 	bool has_registers;
 	unsigned int addr_shift;
 	unsigned int read_mask;
+	unsigned int status_ch_mask;
 	unsigned int data_reg;
 	unsigned long irq_flags;
+	unsigned int num_slots;
 };
 
 /**
@@ -76,6 +82,12 @@ struct ad_sigma_delta {
 	uint8_t			comm;
 
 	const struct ad_sigma_delta_info *info;
+	unsigned int		active_slots;
+	unsigned int		current_slot;
+	bool			status_appended;
+	/* map slots to channels in order to know what to expect from devices */
+	unsigned int		*slots;
+	uint8_t			*samples_buf;
 
 	/*
 	 * DMA (thus cache coherency maintenance) requires the
@@ -97,6 +109,16 @@ static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd,
 	return 0;
 }
 
+static inline int ad_sigma_delta_append_status(struct ad_sigma_delta *sd, bool append)
+{
+	if (sd->info->append_status) {
+		sd->status_appended = append;
+		return sd->info->append_status(sd, append);
+	}
+
+	return 0;
+}
+
 static inline int ad_sigma_delta_set_mode(struct ad_sigma_delta *sd,
 	unsigned int mode)
 {
-- 
2.25.1

Re: [PATCH 3/5] iio: adc: ad_sigma_delta: Add sequencer support

[Jonathan Cameron]

On Wed, 10 Nov 2021 13:17:48 +0200
<alexandru.tachici@analog.com> wrote:

> From: Alexandru Tachici <alexandru.tachici@analog.com>
> 
> Some sigma-delta chips support sampling of multiple
> channels in continuous mode.
> 
> When the operating with more than one channel enabled,
> the channel sequencer cycles through the enabled channels
> in sequential order, from first channel to the last one.
> If a channel is disabled, it is skipped by the sequencer.
> 
> If more than one channel is used in continuous mode,
> instruct the device to append the status to the SPI transfer
> (1 extra byte) every time we receive a sample.
> All sigma-delta chips possessing a sampling sequencer have
> this ability. Inside the status register there will be
> the number of the converted channel. In this way, even
> if the CPU won't keep up with the sampling rate, it won't
> send to userspace wrong channel samples.
> 
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>

Hi Alexandru,

A few comments inline. Approach looks good.

Jonathan

> ---
>  drivers/iio/adc/ad_sigma_delta.c       | 106 ++++++++++++++++++++-----
>  include/linux/iio/adc/ad_sigma_delta.h |  22 +++++
>  2 files changed, 110 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/iio/adc/ad_sigma_delta.c b/drivers/iio/adc/ad_sigma_delta.c
> index 1d652d9b2f5c..d595e7972975 100644
> --- a/drivers/iio/adc/ad_sigma_delta.c
> +++ b/drivers/iio/adc/ad_sigma_delta.c
> @@ -342,33 +342,48 @@ EXPORT_SYMBOL_GPL(ad_sigma_delta_single_conversion);
>  static int ad_sd_buffer_postenable(struct iio_dev *indio_dev)
>  {
>  	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
> -	unsigned int channel;
> +	unsigned int i, slot;
>  	int ret;
>  
> -	channel = find_first_bit(indio_dev->active_scan_mask,
> -				 indio_dev->masklength);
> -	ret = ad_sigma_delta_set_channel(sigma_delta,
> -		indio_dev->channels[channel].address);
> -	if (ret)
> -		return ret;
> +	slot = 0;
> +	for_each_set_bit(i, indio_dev->active_scan_mask, indio_dev->masklength) {
> +		sigma_delta->slots[slot] = indio_dev->channels[i].address;
> +		ret = ad_sigma_delta_set_channel(sigma_delta, indio_dev->channels[i].address);
> +		if (ret)
> +			return ret;
> +		slot++;
> +	}
> +
> +	sigma_delta->active_slots = slot;
> +	sigma_delta->current_slot = 0;
> +
> +	if (sigma_delta->active_slots > 1) {
> +		ret = ad_sigma_delta_append_status(sigma_delta, true);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	kfree(sigma_delta->samples_buf);

krealloc() preferred.   It might not be necessary to actually do an allocation after all
if we happen to have one we can already use.

> +	sigma_delta->samples_buf = kzalloc(slot * indio_dev->channels[0].scan_type.storagebits,
> +					   GFP_KERNEL);

I think this needs space for an aligned timestamp give you pass it directly
to iio_push_to_buffer_with_timestamp();

I haven't checked, but I wonder if the fact you are no longer directly using rx_buf
would allow you to relax the alignment constraint on that. (see below though as I
think you should consider keeping the original path to avoid a copy for the simple
devices).


> +	if (!sigma_delta->samples_buf)
> +		return -ENOMEM;
>  
>  	spi_bus_lock(sigma_delta->spi->master);
>  	sigma_delta->bus_locked = true;
>  	sigma_delta->keep_cs_asserted = true;
>  
>  	ret = ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_CONTINUOUS);
> -	if (ret)
> -		goto err_unlock;
> +	if (ret) {
> +		kfree(sigma_delta->samples_buf);
> +		spi_bus_unlock(sigma_delta->spi->master);

From style point of view preferred to keep to the goto style previously used.
Also, unlock then kfree() buffer + given you pass samples_buf to kfree() on next
run of this function you need to set it to NULL to avoid a double free.


> +		return ret;
> +	}
>  
>  	sigma_delta->irq_dis = false;
>  	enable_irq(sigma_delta->spi->irq);
>  
>  	return 0;
> -
> -err_unlock:
> -	spi_bus_unlock(sigma_delta->spi->master);
> -
> -	return ret;
>  }
>  
>  static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev)
> @@ -386,6 +401,9 @@ static int ad_sd_buffer_postdisable(struct iio_dev *indio_dev)
>  	sigma_delta->keep_cs_asserted = false;
>  	ad_sigma_delta_set_mode(sigma_delta, AD_SD_MODE_IDLE);
>  
> +	if (sigma_delta->status_appended)
> +		ad_sigma_delta_append_status(sigma_delta, false);
> +
>  	sigma_delta->bus_locked = false;
>  	return spi_bus_unlock(sigma_delta->spi->master);
>  }
> @@ -396,6 +414,10 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
>  	struct iio_dev *indio_dev = pf->indio_dev;
>  	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
>  	uint8_t *data = sigma_delta->rx_buf;
> +	unsigned int transfer_size;
> +	unsigned int sample_size;
> +	unsigned int sample_pos;
> +	unsigned int status_pos;
>  	unsigned int reg_size;
>  	unsigned int data_reg;
>  
> @@ -408,20 +430,55 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
>  	else
>  		data_reg = AD_SD_REG_DATA;
>  
> +	/* Status word will be appended to the sample during transfer */
> +	if (sigma_delta->status_appended)
> +		transfer_size = reg_size + 1;
> +	else
> +		transfer_size = reg_size;
> +
>  	switch (reg_size) {
>  	case 4:
>  	case 2:
>  	case 1:
> -		ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size, &data[0]);
> +		status_pos = reg_size;
> +		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[0]);
>  		break;
>  	case 3:
> +		status_pos = reg_size + 1;
>  		/* We store 24 bit samples in a 32 bit word. Keep the upper
>  		 * byte set to zero. */
> -		ad_sd_read_reg_raw(sigma_delta, data_reg, reg_size, &data[1]);
> +		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[1]);
>  		break;
>  	}
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, data, pf->timestamp);

Given lots of drivers don't support scan mode, perhaps you want to keep a fast path that
avoids the extra copies used here? i.e. keep old code in place if active_slots == 1

> +	if (sigma_delta->status_appended) {
> +		u8 converted_channel;
> +
> +		converted_channel = data[status_pos] & sigma_delta->info->status_ch_mask;
> +		if (converted_channel != sigma_delta->slots[sigma_delta->current_slot]) {
> +			/* Desynq occurred during continuous sampling of multiple channels.
/*
 * Desync

preferred though i see we have some other comments in here not using that style.

> +			 * Drop this incomplete sample and start from first channel again.
> +			 */
> +
> +			sigma_delta->current_slot = 0;
> +			iio_trigger_notify_done(indio_dev->trig);
> +			sigma_delta->irq_dis = false;
> +			enable_irq(sigma_delta->spi->irq);
> +
> +			return IRQ_HANDLED;
> +		}
> +	}
> +
> +	sample_size = indio_dev->channels[0].scan_type.storagebits / 8;
> +	sample_pos = sample_size * sigma_delta->current_slot;
> +	memcpy(&sigma_delta->samples_buf[sample_pos], data, sample_size);
> +	sigma_delta->current_slot++;
> +
> +	if (sigma_delta->current_slot == sigma_delta->active_slots) {
> +		sigma_delta->current_slot = 0;
> +		iio_push_to_buffers_with_timestamp(indio_dev, sigma_delta->samples_buf,
> +						   pf->timestamp);
> +	}
>  
>  	iio_trigger_notify_done(indio_dev->trig);
>  	sigma_delta->irq_dis = false;
> @@ -430,10 +487,17 @@ static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
>  	return IRQ_HANDLED;
>  }
>  
> +static bool ad_sd_validate_scan_mask(struct iio_dev *indio_dev, const unsigned long *mask)
> +{
> +	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
> +
> +	return bitmap_weight(mask, indio_dev->masklength) <= sigma_delta->info->num_slots;

I think this requires all existing drivers to have num_slots == 1 to do the same as
iio_validate_scan_mask_onehot. I'm not seeing that change in this patch, or any setting
of the default to 1.

> +}
> +
>  static const struct iio_buffer_setup_ops ad_sd_buffer_setup_ops = {
>  	.postenable = &ad_sd_buffer_postenable,
>  	.postdisable = &ad_sd_buffer_postdisable,
> -	.validate_scan_mask = &iio_validate_scan_mask_onehot,
> +	.validate_scan_mask = &ad_sd_validate_scan_mask,
>  };
>  
>  static irqreturn_t ad_sd_data_rdy_trig_poll(int irq, void *private)
> @@ -517,8 +581,14 @@ static int devm_ad_sd_probe_trigger(struct device *dev, struct iio_dev *indio_de
>   */
>  int devm_ad_sd_setup_buffer_and_trigger(struct device *dev, struct iio_dev *indio_dev)
>  {
> +	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
>  	int ret;
>  
> +	sigma_delta->slots = devm_kcalloc(dev, sigma_delta->info->num_slots,
> +					  sizeof(*sigma_delta->slots), GFP_KERNEL);
> +	if (!sigma_delta->slots)
> +		return -ENOMEM;
> +
>  	ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
>  					      &iio_pollfunc_store_time,
>  					      &ad_sd_trigger_handler,
> diff --git a/include/linux/iio/adc/ad_sigma_delta.h b/include/linux/iio/adc/ad_sigma_delta.h
> index c525fd51652f..758ff25590c3 100644
> --- a/include/linux/iio/adc/ad_sigma_delta.h
> +++ b/include/linux/iio/adc/ad_sigma_delta.h
> @@ -32,6 +32,7 @@ struct iio_dev;
>  /**
>   * struct ad_sigma_delta_info - Sigma Delta driver specific callbacks and options
>   * @set_channel: Will be called to select the current channel, may be NULL.
> + * @append_status: Will be called to enable status append at the end of the sample, may be NULL.
>   * @set_mode: Will be called to select the current mode, may be NULL.
>   * @postprocess_sample: Is called for each sampled data word, can be used to
>   *		modify or drop the sample data, it, may be NULL.
> @@ -39,19 +40,24 @@ struct iio_dev;
>   *		if there is just one read-only sample data shift register.
>   * @addr_shift: Shift of the register address in the communications register.
>   * @read_mask: Mask for the communications register having the read bit set.
> + * @status_ch_mask: Mask for the channel number stored in status register.
>   * @data_reg: Address of the data register, if 0 the default address of 0x3 will
>   *   be used.
>   * @irq_flags: flags for the interrupt used by the triggered buffer
> + * @num_slots: Number of sequencer slots
>   */
>  struct ad_sigma_delta_info {
>  	int (*set_channel)(struct ad_sigma_delta *, unsigned int channel);
> +	int (*append_status)(struct ad_sigma_delta *, bool append);
>  	int (*set_mode)(struct ad_sigma_delta *, enum ad_sigma_delta_mode mode);
>  	int (*postprocess_sample)(struct ad_sigma_delta *, unsigned int raw_sample);
>  	bool has_registers;
>  	unsigned int addr_shift;
>  	unsigned int read_mask;
> +	unsigned int status_ch_mask;
>  	unsigned int data_reg;
>  	unsigned long irq_flags;
> +	unsigned int num_slots;
>  };
>  
>  /**
> @@ -76,6 +82,12 @@ struct ad_sigma_delta {
>  	uint8_t			comm;
>  
>  	const struct ad_sigma_delta_info *info;
> +	unsigned int		active_slots;
> +	unsigned int		current_slot;
> +	bool			status_appended;
> +	/* map slots to channels in order to know what to expect from devices */
> +	unsigned int		*slots;
> +	uint8_t			*samples_buf;
>  
>  	/*
>  	 * DMA (thus cache coherency maintenance) requires the
> @@ -97,6 +109,16 @@ static inline int ad_sigma_delta_set_channel(struct ad_sigma_delta *sd,
>  	return 0;
>  }
>  
> +static inline int ad_sigma_delta_append_status(struct ad_sigma_delta *sd, bool append)
> +{
> +	if (sd->info->append_status) {
> +		sd->status_appended = append;
> +		return sd->info->append_status(sd, append);
> +	}
> +
> +	return 0;
> +}
> +
>  static inline int ad_sigma_delta_set_mode(struct ad_sigma_delta *sd,
>  	unsigned int mode)
>  {

Re: [PATCH 3/5] iio: adc: ad_sigma_delta: Add sequencer support

[Andy Shevchenko]

On Fri, Nov 12, 2021 at 7:10 PM Jonathan Cameron <jic23@kernel.org> wrote:
> On Wed, 10 Nov 2021 13:17:48 +0200
> <alexandru.tachici@analog.com> wrote:


> > +     kfree(sigma_delta->samples_buf);
>
> krealloc() preferred.   It might not be necessary to actually do an allocation after all
> if we happen to have one we can already use.

Looking at below, shouldn't it be krealloc_array()?

> > +     sigma_delta->samples_buf = kzalloc(slot * indio_dev->channels[0].scan_type.storagebits,
> > +                                        GFP_KERNEL);


-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 3/5] iio: adc: ad_sigma_delta: Add sequencer support

[Jonathan Cameron]

On Sat, 13 Nov 2021 19:00:11 +0200
Andy Shevchenko <andy.shevchenko@gmail.com> wrote:

> On Fri, Nov 12, 2021 at 7:10 PM Jonathan Cameron <jic23@kernel.org> wrote:
> > On Wed, 10 Nov 2021 13:17:48 +0200
> > <alexandru.tachici@analog.com> wrote:  
> 
> 
> > > +     kfree(sigma_delta->samples_buf);  
> >
> > krealloc() preferred.   It might not be necessary to actually do an allocation after all
> > if we happen to have one we can already use.  
> 
> Looking at below, shouldn't it be krealloc_array()?

True

> 
> > > +     sigma_delta->samples_buf = kzalloc(slot * indio_dev->channels[0].scan_type.storagebits,
> > > +                                        GFP_KERNEL);  
> 
> 

[PATCH 4/5] iio: adc: ad7124: add sequencer support

[alexandru.tachici]

From: Alexandru Tachici <alexandru.tachici@analog.com>

Add sequencer support for AD7124.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
---
 drivers/iio/adc/ad7124.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7124.c b/drivers/iio/adc/ad7124.c
index 30299b899799..5760a222df5f 100644
--- a/drivers/iio/adc/ad7124.c
+++ b/drivers/iio/adc/ad7124.c
@@ -43,6 +43,8 @@
 #define AD7124_STATUS_POR_FLAG_MSK	BIT(4)
 
 /* AD7124_ADC_CONTROL */
+#define AD7124_ADC_STATUS_EN_MSK	BIT(10)
+#define AD7124_ADC_STATUS_EN(x)		FIELD_PREP(AD7124_ADC_STATUS_EN_MSK, x)
 #define AD7124_ADC_CTRL_REF_EN_MSK	BIT(8)
 #define AD7124_ADC_CTRL_REF_EN(x)	FIELD_PREP(AD7124_ADC_CTRL_REF_EN_MSK, x)
 #define AD7124_ADC_CTRL_PWR_MSK	GENMASK(7, 6)
@@ -512,14 +514,27 @@ static int ad7124_set_channel(struct ad_sigma_delta *sd, unsigned int channel)
 	return ret;
 }
 
+static int ad7124_append_status(struct ad_sigma_delta *sd, bool append)
+{
+	struct ad7124_state *st = container_of(sd, struct ad7124_state, sd);
+
+	st->adc_control &= ~AD7124_ADC_STATUS_EN_MSK;
+	st->adc_control |= AD7124_ADC_STATUS_EN(append);
+
+	return ad_sd_write_reg(&st->sd, AD7124_ADC_CONTROL, 2, st->adc_control);
+}
+
 static const struct ad_sigma_delta_info ad7124_sigma_delta_info = {
 	.set_channel = ad7124_set_channel,
+	.append_status = ad7124_append_status,
 	.set_mode = ad7124_set_mode,
 	.has_registers = true,
 	.addr_shift = 0,
 	.read_mask = BIT(6),
+	.status_ch_mask = GENMASK(3, 0),
 	.data_reg = AD7124_DATA,
-	.irq_flags = IRQF_TRIGGER_FALLING
+	.num_slots = 8,
+	.irq_flags = IRQF_TRIGGER_FALLING,
 };
 
 static int ad7124_read_raw(struct iio_dev *indio_dev,
-- 
2.25.1

[PATCH 5/5] iio: adc: ad7192: add sequencer support

[alexandru.tachici]

From: Alexandru Tachici <alexandru.tachici@analog.com>

Add sequencer support for AD7192.

Signed-off-by: Alexandru Tachici <alexandru.tachici@analog.com>
---
 drivers/iio/adc/ad7192.c | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/adc/ad7192.c b/drivers/iio/adc/ad7192.c
index 1fc0f4eb858e..e70f86d9a219 100644
--- a/drivers/iio/adc/ad7192.c
+++ b/drivers/iio/adc/ad7192.c
@@ -58,7 +58,8 @@
 /* Mode Register Bit Designations (AD7192_REG_MODE) */
 #define AD7192_MODE_SEL(x)	(((x) & 0x7) << 21) /* Operation Mode Select */
 #define AD7192_MODE_SEL_MASK	(0x7 << 21) /* Operation Mode Select Mask */
-#define AD7192_MODE_DAT_STA	BIT(20) /* Status Register transmission */
+#define AD7192_MODE_STA(x)	(((x) & 0x1) << 20) /* Status Register transmission */
+#define AD7192_MODE_STA_MASK	BIT(20) /* Status Register transmission Mask */
 #define AD7192_MODE_CLKSRC(x)	(((x) & 0x3) << 18) /* Clock Source Select */
 #define AD7192_MODE_SINC3	BIT(15) /* SINC3 Filter Select */
 #define AD7192_MODE_ACX		BIT(14) /* AC excitation enable(AD7195 only)*/
@@ -287,12 +288,25 @@ static int ad7192_set_mode(struct ad_sigma_delta *sd,
 	return ad_sd_write_reg(&st->sd, AD7192_REG_MODE, 3, st->mode);
 }
 
+static int ad7192_append_status(struct ad_sigma_delta *sd, bool append)
+{
+	struct ad7192_state *st = ad_sigma_delta_to_ad7192(sd);
+
+	st->mode &= ~AD7192_MODE_STA_MASK;
+	st->mode |= AD7192_MODE_STA(append);
+
+	return ad_sd_write_reg(&st->sd, AD7192_REG_MODE, 3, st->mode);
+}
+
 static const struct ad_sigma_delta_info ad7192_sigma_delta_info = {
 	.set_channel = ad7192_set_channel,
+	.append_status = ad7192_append_status,
 	.set_mode = ad7192_set_mode,
 	.has_registers = true,
 	.addr_shift = 3,
 	.read_mask = BIT(6),
+	.status_ch_mask = GENMASK(3, 0),
+	.num_slots = 4,
 	.irq_flags = IRQF_TRIGGER_FALLING,
 };
 
-- 
2.25.1