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

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

[kernel test robot]

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CC: kbuild-all(a)lists.01.org
In-Reply-To: <20211110111750.27263-4-alexandru.tachici@analog.com>
References: <20211110111750.27263-4-alexandru.tachici@analog.com>
TO: alexandru.tachici(a)analog.com
TO: linux-iio(a)vger.kernel.org
TO: linux-kernel(a)vger.kernel.org
CC: jic23(a)kernel.org
CC: Alexandru Tachici <alexandru.tachici@analog.com>
CC: "Lars-Peter Clausen" <lars@metafoo.de>

Hi,

I love your patch! Perhaps something to improve:

[auto build test WARNING on jic23-iio/togreg]
[also build test WARNING on linux/master linus/master v5.16-rc1 next-20211118]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/alexandru-tachici-analog-com/iio-adc-ad_sigma_delta-Add-sequencer-support/20211110-190925
base:   https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git togreg
:::::: branch date: 9 days ago
:::::: commit date: 9 days ago
config: i386-randconfig-m021-20211115 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>

smatch warnings:
drivers/iio/adc/ad_sigma_delta.c:457 ad_sd_trigger_handler() error: uninitialized symbol 'status_pos'.

vim +/status_pos +457 drivers/iio/adc/ad_sigma_delta.c

af3008485ea037 Lars-Peter Clausen 2012-08-10  410  
af3008485ea037 Lars-Peter Clausen 2012-08-10  411  static irqreturn_t ad_sd_trigger_handler(int irq, void *p)
af3008485ea037 Lars-Peter Clausen 2012-08-10  412  {
af3008485ea037 Lars-Peter Clausen 2012-08-10  413  	struct iio_poll_func *pf = p;
af3008485ea037 Lars-Peter Clausen 2012-08-10  414  	struct iio_dev *indio_dev = pf->indio_dev;
af3008485ea037 Lars-Peter Clausen 2012-08-10  415  	struct ad_sigma_delta *sigma_delta = iio_device_get_drvdata(indio_dev);
0fb6ee8d0b5e90 Lars-Peter Clausen 2020-11-24  416  	uint8_t *data = sigma_delta->rx_buf;
1d2220fad25a99 Alexandru Tachici  2021-11-10  417  	unsigned int transfer_size;
1d2220fad25a99 Alexandru Tachici  2021-11-10  418  	unsigned int sample_size;
1d2220fad25a99 Alexandru Tachici  2021-11-10  419  	unsigned int sample_pos;
1d2220fad25a99 Alexandru Tachici  2021-11-10  420  	unsigned int status_pos;
af3008485ea037 Lars-Peter Clausen 2012-08-10  421  	unsigned int reg_size;
f0aef2d0186431 Lars-Peter Clausen 2018-11-13  422  	unsigned int data_reg;
af3008485ea037 Lars-Peter Clausen 2012-08-10  423  
af3008485ea037 Lars-Peter Clausen 2012-08-10  424  	reg_size = indio_dev->channels[0].scan_type.realbits +
af3008485ea037 Lars-Peter Clausen 2012-08-10  425  			indio_dev->channels[0].scan_type.shift;
af3008485ea037 Lars-Peter Clausen 2012-08-10  426  	reg_size = DIV_ROUND_UP(reg_size, 8);
af3008485ea037 Lars-Peter Clausen 2012-08-10  427  
f0aef2d0186431 Lars-Peter Clausen 2018-11-13  428  	if (sigma_delta->info->data_reg != 0)
f0aef2d0186431 Lars-Peter Clausen 2018-11-13  429  		data_reg = sigma_delta->info->data_reg;
f0aef2d0186431 Lars-Peter Clausen 2018-11-13  430  	else
f0aef2d0186431 Lars-Peter Clausen 2018-11-13  431  		data_reg = AD_SD_REG_DATA;
f0aef2d0186431 Lars-Peter Clausen 2018-11-13  432  
1d2220fad25a99 Alexandru Tachici  2021-11-10  433  	/* Status word will be appended to the sample during transfer */
1d2220fad25a99 Alexandru Tachici  2021-11-10  434  	if (sigma_delta->status_appended)
1d2220fad25a99 Alexandru Tachici  2021-11-10  435  		transfer_size = reg_size + 1;
1d2220fad25a99 Alexandru Tachici  2021-11-10  436  	else
1d2220fad25a99 Alexandru Tachici  2021-11-10  437  		transfer_size = reg_size;
1d2220fad25a99 Alexandru Tachici  2021-11-10  438  
af3008485ea037 Lars-Peter Clausen 2012-08-10  439  	switch (reg_size) {
af3008485ea037 Lars-Peter Clausen 2012-08-10  440  	case 4:
af3008485ea037 Lars-Peter Clausen 2012-08-10  441  	case 2:
af3008485ea037 Lars-Peter Clausen 2012-08-10  442  	case 1:
1d2220fad25a99 Alexandru Tachici  2021-11-10  443  		status_pos = reg_size;
1d2220fad25a99 Alexandru Tachici  2021-11-10  444  		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[0]);
af3008485ea037 Lars-Peter Clausen 2012-08-10  445  		break;
af3008485ea037 Lars-Peter Clausen 2012-08-10  446  	case 3:
1d2220fad25a99 Alexandru Tachici  2021-11-10  447  		status_pos = reg_size + 1;
af3008485ea037 Lars-Peter Clausen 2012-08-10  448  		/* We store 24 bit samples in a 32 bit word. Keep the upper
af3008485ea037 Lars-Peter Clausen 2012-08-10  449  		 * byte set to zero. */
1d2220fad25a99 Alexandru Tachici  2021-11-10  450  		ad_sd_read_reg_raw(sigma_delta, data_reg, transfer_size, &data[1]);
af3008485ea037 Lars-Peter Clausen 2012-08-10  451  		break;
af3008485ea037 Lars-Peter Clausen 2012-08-10  452  	}
af3008485ea037 Lars-Peter Clausen 2012-08-10  453  
1d2220fad25a99 Alexandru Tachici  2021-11-10  454  	if (sigma_delta->status_appended) {
1d2220fad25a99 Alexandru Tachici  2021-11-10  455  		u8 converted_channel;
1d2220fad25a99 Alexandru Tachici  2021-11-10  456  
1d2220fad25a99 Alexandru Tachici  2021-11-10 @457  		converted_channel = data[status_pos] & sigma_delta->info->status_ch_mask;
1d2220fad25a99 Alexandru Tachici  2021-11-10  458  		if (converted_channel != sigma_delta->slots[sigma_delta->current_slot]) {
1d2220fad25a99 Alexandru Tachici  2021-11-10  459  			/* Desynq occurred during continuous sampling of multiple channels.
1d2220fad25a99 Alexandru Tachici  2021-11-10  460  			 * Drop this incomplete sample and start from first channel again.
1d2220fad25a99 Alexandru Tachici  2021-11-10  461  			 */
1d2220fad25a99 Alexandru Tachici  2021-11-10  462  
1d2220fad25a99 Alexandru Tachici  2021-11-10  463  			sigma_delta->current_slot = 0;
1d2220fad25a99 Alexandru Tachici  2021-11-10  464  			iio_trigger_notify_done(indio_dev->trig);
1d2220fad25a99 Alexandru Tachici  2021-11-10  465  			sigma_delta->irq_dis = false;
1d2220fad25a99 Alexandru Tachici  2021-11-10  466  			enable_irq(sigma_delta->spi->irq);
1d2220fad25a99 Alexandru Tachici  2021-11-10  467  
1d2220fad25a99 Alexandru Tachici  2021-11-10  468  			return IRQ_HANDLED;
1d2220fad25a99 Alexandru Tachici  2021-11-10  469  		}
1d2220fad25a99 Alexandru Tachici  2021-11-10  470  	}
1d2220fad25a99 Alexandru Tachici  2021-11-10  471  
1d2220fad25a99 Alexandru Tachici  2021-11-10  472  	sample_size = indio_dev->channels[0].scan_type.storagebits / 8;
1d2220fad25a99 Alexandru Tachici  2021-11-10  473  	sample_pos = sample_size * sigma_delta->current_slot;
1d2220fad25a99 Alexandru Tachici  2021-11-10  474  	memcpy(&sigma_delta->samples_buf[sample_pos], data, sample_size);
1d2220fad25a99 Alexandru Tachici  2021-11-10  475  	sigma_delta->current_slot++;
1d2220fad25a99 Alexandru Tachici  2021-11-10  476  
1d2220fad25a99 Alexandru Tachici  2021-11-10  477  	if (sigma_delta->current_slot == sigma_delta->active_slots) {
1d2220fad25a99 Alexandru Tachici  2021-11-10  478  		sigma_delta->current_slot = 0;
1d2220fad25a99 Alexandru Tachici  2021-11-10  479  		iio_push_to_buffers_with_timestamp(indio_dev, sigma_delta->samples_buf,
1d2220fad25a99 Alexandru Tachici  2021-11-10  480  						   pf->timestamp);
1d2220fad25a99 Alexandru Tachici  2021-11-10  481  	}
af3008485ea037 Lars-Peter Clausen 2012-08-10  482  
af3008485ea037 Lars-Peter Clausen 2012-08-10  483  	iio_trigger_notify_done(indio_dev->trig);
af3008485ea037 Lars-Peter Clausen 2012-08-10  484  	sigma_delta->irq_dis = false;
af3008485ea037 Lars-Peter Clausen 2012-08-10  485  	enable_irq(sigma_delta->spi->irq);
af3008485ea037 Lars-Peter Clausen 2012-08-10  486  
af3008485ea037 Lars-Peter Clausen 2012-08-10  487  	return IRQ_HANDLED;
af3008485ea037 Lars-Peter Clausen 2012-08-10  488  }
af3008485ea037 Lars-Peter Clausen 2012-08-10  489  

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all(a)lists.01.org

[-- Attachment #2: config.gz --]
[-- Type: application/gzip, Size: 38013 bytes --]

[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 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);  
> 
>