diff mbox series

[v1] iio: adc: add buffering support to the TI LMP92064 ADC driver

Message ID 20230614075537.3525194-1-l.goehrs@pengutronix.de
State New
Headers
Series [v1] iio: adc: add buffering support to the TI LMP92064 ADC driver |

Commit Message

Leonard Göhrs June 14, 2023, 7:55 a.m. UTC 
  Enable buffered reading of samples from the LMP92064 ADC.
The main benefit of this change is being able to read out current and
voltage measurements in a single transfer, allowing instantaneous power
measurements.

Reads into the buffer can be triggered by any software triggers, e.g.
the iio-trig-hrtimer:

    $ mkdir /sys/kernel/config/iio/triggers/hrtimer/my-trigger
    $ cat /sys/bus/iio/devices/iio\:device3/name
    lmp92064
    $ iio_readdev -t my-trigger -b 16 iio:device3 | hexdump
    WARNING: High-speed mode not enabled
    0000000 0000 0176 0101 0001 5507 abd5 7645 1768
    0000010 0000 016d 0101 0001 ee1e ac6b 7645 1768
    ...

Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
---
 drivers/iio/adc/ti-lmp92064.c | 54 +++++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)


base-commit: 9561de3a55bed6bdd44a12820ba81ec416e705a7

Comments

Lars-Peter Clausen June 14, 2023, 11:59 a.m. UTC | #1 
On 6/14/23 00:55, Leonard Göhrs wrote:
> Enable buffered reading of samples from the LMP92064 ADC.
> The main benefit of this change is being able to read out current and
> voltage measurements in a single transfer, allowing instantaneous power
> measurements.
>
> Reads into the buffer can be triggered by any software triggers, e.g.
> the iio-trig-hrtimer:
>
>      $ mkdir /sys/kernel/config/iio/triggers/hrtimer/my-trigger
>      $ cat /sys/bus/iio/devices/iio\:device3/name
>      lmp92064
>      $ iio_readdev -t my-trigger -b 16 iio:device3 | hexdump
>      WARNING: High-speed mode not enabled
>      0000000 0000 0176 0101 0001 5507 abd5 7645 1768
>      0000010 0000 016d 0101 0001 ee1e ac6b 7645 1768
>      ...
>
> Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>

Patch looks good. A small comment for an improvement, but not a most have.

> ---
>   drivers/iio/adc/ti-lmp92064.c | 54 +++++++++++++++++++++++++++++++++++
>   1 file changed, 54 insertions(+)
>
> diff --git a/drivers/iio/adc/ti-lmp92064.c b/drivers/iio/adc/ti-lmp92064.c
> index c30ed824924f3..03765c4057dda 100644
> --- a/drivers/iio/adc/ti-lmp92064.c
> +++ b/drivers/iio/adc/ti-lmp92064.c
> @@ -16,7 +16,10 @@
>   #include <linux/spi/spi.h>
>   
>   #include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
>   #include <linux/iio/driver.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
>   
>   #define TI_LMP92064_REG_CONFIG_A 0x0000
>   #define TI_LMP92064_REG_CONFIG_B 0x0001
> @@ -91,6 +94,13 @@ static const struct iio_chan_spec lmp92064_adc_channels[] = {
>   		.address = TI_LMP92064_CHAN_INC,
>   		.info_mask_separate =
>   			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +			.shift = 0,
> +		},
>   		.datasheet_name = "INC",
>   	},
>   	{
> @@ -98,8 +108,16 @@ static const struct iio_chan_spec lmp92064_adc_channels[] = {
>   		.address = TI_LMP92064_CHAN_INV,
>   		.info_mask_separate =
>   			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 1,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +			.shift = 0,
> +		},
>   		.datasheet_name = "INV",
>   	},
> +	IIO_CHAN_SOFT_TIMESTAMP(2),
>   };
>   
>   static int lmp92064_read_meas(struct lmp92064_adc_priv *priv, u16 *res)
> @@ -171,6 +189,37 @@ static int lmp92064_read_raw(struct iio_dev *indio_dev,
>   	}
>   }
>   
> +static irqreturn_t lmp92064_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct lmp92064_adc_priv *priv = iio_priv(indio_dev);
> +	int i = 0, j, ret;
> +	u16 raw[2];
> +	u16 *data;
> +
> +	ret = lmp92064_read_meas(priv, raw);
> +	if (ret < 0)
> +		goto done;
> +
> +	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
> +	if (!data)
> +		goto done;
If you want to avoid allocating the buffer each time a sample-set is 
captured you can register the `update_scan_mode` callback and allocate 
the buffer in there. Or if you know the upper limit of your buffer size, 
base on number of channels, and its small you can also use a one time 
allocation directly embedded in the priv struct.
> +
> +	for_each_set_bit(j, indio_dev->active_scan_mask, indio_dev->masklength)
> +		data[i++] = raw[j];
> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, data,
> +					   iio_get_time_ns(indio_dev));
> +
> +	kfree(data);
> +
> +done:
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
]...\
Jonathan Cameron June 17, 2023, 6:27 p.m. UTC | #2 
On Wed, 14 Jun 2023 09:55:36 +0200
Leonard Göhrs <l.goehrs@pengutronix.de> wrote:

> Enable buffered reading of samples from the LMP92064 ADC.
> The main benefit of this change is being able to read out current and
> voltage measurements in a single transfer, allowing instantaneous power
> measurements.
> 
> Reads into the buffer can be triggered by any software triggers, e.g.
> the iio-trig-hrtimer:
> 
>     $ mkdir /sys/kernel/config/iio/triggers/hrtimer/my-trigger
>     $ cat /sys/bus/iio/devices/iio\:device3/name
>     lmp92064
>     $ iio_readdev -t my-trigger -b 16 iio:device3 | hexdump
>     WARNING: High-speed mode not enabled
>     0000000 0000 0176 0101 0001 5507 abd5 7645 1768
>     0000010 0000 016d 0101 0001 ee1e ac6b 7645 1768
>     ...
> 
> Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
> ---
>  drivers/iio/adc/ti-lmp92064.c | 54 +++++++++++++++++++++++++++++++++++
>  1 file changed, 54 insertions(+)
> 
> diff --git a/drivers/iio/adc/ti-lmp92064.c b/drivers/iio/adc/ti-lmp92064.c
> index c30ed824924f3..03765c4057dda 100644
> --- a/drivers/iio/adc/ti-lmp92064.c
> +++ b/drivers/iio/adc/ti-lmp92064.c
> @@ -16,7 +16,10 @@
>  #include <linux/spi/spi.h>
>  
>  #include <linux/iio/iio.h>
> +#include <linux/iio/buffer.h>
>  #include <linux/iio/driver.h>
> +#include <linux/iio/triggered_buffer.h>
> +#include <linux/iio/trigger_consumer.h>
>  
>  #define TI_LMP92064_REG_CONFIG_A 0x0000
>  #define TI_LMP92064_REG_CONFIG_B 0x0001
> @@ -91,6 +94,13 @@ static const struct iio_chan_spec lmp92064_adc_channels[] = {
>  		.address = TI_LMP92064_CHAN_INC,
>  		.info_mask_separate =
>  			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 0,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +			.shift = 0,

As zero is the 'obvious' default for shift (do nothing case) and c will set it to 0 for
you anyway, no need to set it explicitly like this.

> +		},
>  		.datasheet_name = "INC",
>  	},
>  	{
> @@ -98,8 +108,16 @@ static const struct iio_chan_spec lmp92064_adc_channels[] = {
>  		.address = TI_LMP92064_CHAN_INV,
>  		.info_mask_separate =
>  			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
> +		.scan_index = 1,
> +		.scan_type = {
> +			.sign = 'u',
> +			.realbits = 12,
> +			.storagebits = 16,
> +			.shift = 0,

Same here. No need for this last line.

> +		},
>  		.datasheet_name = "INV",
>  	},
> +	IIO_CHAN_SOFT_TIMESTAMP(2),
>  };
>  
>  static int lmp92064_read_meas(struct lmp92064_adc_priv *priv, u16 *res)
> @@ -171,6 +189,37 @@ static int lmp92064_read_raw(struct iio_dev *indio_dev,
>  	}
>  }
>  
> +static irqreturn_t lmp92064_trigger_handler(int irq, void *p)
> +{
> +	struct iio_poll_func *pf = p;
> +	struct iio_dev *indio_dev = pf->indio_dev;
> +	struct lmp92064_adc_priv *priv = iio_priv(indio_dev);
> +	int i = 0, j, ret;
> +	u16 raw[2];
> +	u16 *data;
> +
> +	ret = lmp92064_read_meas(priv, raw);
> +	if (ret < 0)
> +		goto done;
> +
> +	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);

A driver shouldn't be directly accessing scan_bytes.
You will see iio.h that it is marked [INTERN] to show it should only be accessed
by the IIO core code.

The reasoning is closely related to Lars' point. This is almost always a small
structure with a known maximum size (across all possible channel configurations)
so allocate that space once not every scan (will be 16 bytes I think)


> +	if (!data)
> +		goto done;
> +
> +	for_each_set_bit(j, indio_dev->active_scan_mask, indio_dev->masklength)
> +		data[i++] = raw[j];
When a sensor 'always' reads the two channels, we can leave the necessary data
mangling up to the IIO core.

Provide available_scan_masks and then always push the lot every time.
Mostly people will want both channels anyway (as they paid for them ;)
so that core code that moves the data around will do nothing.  In the cases
where they only want one channel it will handle the complexity for you.

> +
> +	iio_push_to_buffers_with_timestamp(indio_dev, data,
> +					   iio_get_time_ns(indio_dev));
> +
> +	kfree(data);
> +
> +done:
> +	iio_trigger_notify_done(indio_dev->trig);
> +
> +	return IRQ_HANDLED;
> +}
> +
>  static int lmp92064_reset(struct lmp92064_adc_priv *priv,
>  			  struct gpio_desc *gpio_reset)
>  {
> @@ -302,6 +351,11 @@ static int lmp92064_adc_probe(struct spi_device *spi)
>  	indio_dev->num_channels = ARRAY_SIZE(lmp92064_adc_channels);
>  	indio_dev->info = &lmp92064_adc_info;
>  
> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
> +					      lmp92064_trigger_handler, NULL);
> +	if (ret)
> +		return dev_err_probe(dev, ret, "Failed to setup buffered read\n");
> +
>  	return devm_iio_device_register(dev, indio_dev);
>  }
>  
> 
> base-commit: 9561de3a55bed6bdd44a12820ba81ec416e705a7
Leonard Göhrs June 22, 2023, 7:05 a.m. UTC | #3 
On 17.06.23 20:27, Jonathan Cameron wrote:
> On Wed, 14 Jun 2023 09:55:36 +0200
> Leonard Göhrs <l.goehrs@pengutronix.de> wrote:
> 
>> Enable buffered reading of samples from the LMP92064 ADC.
>> The main benefit of this change is being able to read out current and
>> voltage measurements in a single transfer, allowing instantaneous power
>> measurements.
>>
>> Reads into the buffer can be triggered by any software triggers, e.g.
>> the iio-trig-hrtimer:
>>
>>      $ mkdir /sys/kernel/config/iio/triggers/hrtimer/my-trigger
>>      $ cat /sys/bus/iio/devices/iio\:device3/name
>>      lmp92064
>>      $ iio_readdev -t my-trigger -b 16 iio:device3 | hexdump
>>      WARNING: High-speed mode not enabled
>>      0000000 0000 0176 0101 0001 5507 abd5 7645 1768
>>      0000010 0000 016d 0101 0001 ee1e ac6b 7645 1768
>>      ...
>>
>> Signed-off-by: Leonard Göhrs <l.goehrs@pengutronix.de>
>> ---
>>   drivers/iio/adc/ti-lmp92064.c | 54 +++++++++++++++++++++++++++++++++++
>>   1 file changed, 54 insertions(+)
>>
>> diff --git a/drivers/iio/adc/ti-lmp92064.c b/drivers/iio/adc/ti-lmp92064.c
>> index c30ed824924f3..03765c4057dda 100644
>> --- a/drivers/iio/adc/ti-lmp92064.c
>> +++ b/drivers/iio/adc/ti-lmp92064.c
>> @@ -16,7 +16,10 @@
>>   #include <linux/spi/spi.h>
>>   
>>   #include <linux/iio/iio.h>
>> +#include <linux/iio/buffer.h>
>>   #include <linux/iio/driver.h>
>> +#include <linux/iio/triggered_buffer.h>
>> +#include <linux/iio/trigger_consumer.h>
>>   
>>   #define TI_LMP92064_REG_CONFIG_A 0x0000
>>   #define TI_LMP92064_REG_CONFIG_B 0x0001
>> @@ -91,6 +94,13 @@ static const struct iio_chan_spec lmp92064_adc_channels[] = {
>>   		.address = TI_LMP92064_CHAN_INC,
>>   		.info_mask_separate =
>>   			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
>> +		.scan_index = 0,
>> +		.scan_type = {
>> +			.sign = 'u',
>> +			.realbits = 12,
>> +			.storagebits = 16,
>> +			.shift = 0,
> 
> As zero is the 'obvious' default for shift (do nothing case) and c will set it to 0 for
> you anyway, no need to set it explicitly like this.
> 
>> +		},
>>   		.datasheet_name = "INC",
>>   	},
>>   	{
>> @@ -98,8 +108,16 @@ static const struct iio_chan_spec lmp92064_adc_channels[] = {
>>   		.address = TI_LMP92064_CHAN_INV,
>>   		.info_mask_separate =
>>   			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
>> +		.scan_index = 1,
>> +		.scan_type = {
>> +			.sign = 'u',
>> +			.realbits = 12,
>> +			.storagebits = 16,
>> +			.shift = 0,
> 
> Same here. No need for this last line.
> 
>> +		},
>>   		.datasheet_name = "INV",
>>   	},
>> +	IIO_CHAN_SOFT_TIMESTAMP(2),
>>   };
>>   
>>   static int lmp92064_read_meas(struct lmp92064_adc_priv *priv, u16 *res)
>> @@ -171,6 +189,37 @@ static int lmp92064_read_raw(struct iio_dev *indio_dev,
>>   	}
>>   }
>>   
>> +static irqreturn_t lmp92064_trigger_handler(int irq, void *p)
>> +{
>> +	struct iio_poll_func *pf = p;
>> +	struct iio_dev *indio_dev = pf->indio_dev;
>> +	struct lmp92064_adc_priv *priv = iio_priv(indio_dev);
>> +	int i = 0, j, ret;
>> +	u16 raw[2];
>> +	u16 *data;
>> +
>> +	ret = lmp92064_read_meas(priv, raw);
>> +	if (ret < 0)
>> +		goto done;
>> +
>> +	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
> 
> A driver shouldn't be directly accessing scan_bytes.
> You will see iio.h that it is marked [INTERN] to show it should only be accessed
> by the IIO core code.
> 
> The reasoning is closely related to Lars' point. This is almost always a small
> structure with a known maximum size (across all possible channel configurations)
> so allocate that space once not every scan (will be 16 bytes I think)

Sounds reasonable. I've more or less copied the trigger handler from
iio_simple_dummy_buffer.c assuming it contained the best practice when
it comes to buffer handling w.r.t. size and alignment (which I was not quite
sure about how to do right).

I've sent a V2 now that uses a stack allocated structure as buffer. This makes
the whole trigger handler a lot more concise.

>> +	if (!data)
>> +		goto done;
>> +
>> +	for_each_set_bit(j, indio_dev->active_scan_mask, indio_dev->masklength)
>> +		data[i++] = raw[j];
> When a sensor 'always' reads the two channels, we can leave the necessary data
> mangling up to the IIO core.
> 
> Provide available_scan_masks and then always push the lot every time.
> Mostly people will want both channels anyway (as they paid for them ;)
> so that core code that moves the data around will do nothing.  In the cases
> where they only want one channel it will handle the complexity for you.

Thanks for the tip! This simplifies the trigger handler even further.

>> +
>> +	iio_push_to_buffers_with_timestamp(indio_dev, data,
>> +					   iio_get_time_ns(indio_dev));
>> +
>> +	kfree(data);
>> +
>> +done:
>> +	iio_trigger_notify_done(indio_dev->trig);
>> +
>> +	return IRQ_HANDLED;
>> +}
>> +
>>   static int lmp92064_reset(struct lmp92064_adc_priv *priv,
>>   			  struct gpio_desc *gpio_reset)
>>   {
>> @@ -302,6 +351,11 @@ static int lmp92064_adc_probe(struct spi_device *spi)
>>   	indio_dev->num_channels = ARRAY_SIZE(lmp92064_adc_channels);
>>   	indio_dev->info = &lmp92064_adc_info;
>>   
>> +	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
>> +					      lmp92064_trigger_handler, NULL);
>> +	if (ret)
>> +		return dev_err_probe(dev, ret, "Failed to setup buffered read\n");
>> +
>>   	return devm_iio_device_register(dev, indio_dev);
>>   }
>>   
>>
>> base-commit: 9561de3a55bed6bdd44a12820ba81ec416e705a7
> 
>
diff mbox series

Patch

diff --git a/drivers/iio/adc/ti-lmp92064.c b/drivers/iio/adc/ti-lmp92064.c
index c30ed824924f3..03765c4057dda 100644
--- a/drivers/iio/adc/ti-lmp92064.c
+++ b/drivers/iio/adc/ti-lmp92064.c
@@ -16,7 +16,10 @@ 
 #include <linux/spi/spi.h>
 
 #include <linux/iio/iio.h>
+#include <linux/iio/buffer.h>
 #include <linux/iio/driver.h>
+#include <linux/iio/triggered_buffer.h>
+#include <linux/iio/trigger_consumer.h>
 
 #define TI_LMP92064_REG_CONFIG_A 0x0000
 #define TI_LMP92064_REG_CONFIG_B 0x0001
@@ -91,6 +94,13 @@  static const struct iio_chan_spec lmp92064_adc_channels[] = {
 		.address = TI_LMP92064_CHAN_INC,
 		.info_mask_separate =
 			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 0,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 12,
+			.storagebits = 16,
+			.shift = 0,
+		},
 		.datasheet_name = "INC",
 	},
 	{
@@ -98,8 +108,16 @@  static const struct iio_chan_spec lmp92064_adc_channels[] = {
 		.address = TI_LMP92064_CHAN_INV,
 		.info_mask_separate =
 			BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
+		.scan_index = 1,
+		.scan_type = {
+			.sign = 'u',
+			.realbits = 12,
+			.storagebits = 16,
+			.shift = 0,
+		},
 		.datasheet_name = "INV",
 	},
+	IIO_CHAN_SOFT_TIMESTAMP(2),
 };
 
 static int lmp92064_read_meas(struct lmp92064_adc_priv *priv, u16 *res)
@@ -171,6 +189,37 @@  static int lmp92064_read_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static irqreturn_t lmp92064_trigger_handler(int irq, void *p)
+{
+	struct iio_poll_func *pf = p;
+	struct iio_dev *indio_dev = pf->indio_dev;
+	struct lmp92064_adc_priv *priv = iio_priv(indio_dev);
+	int i = 0, j, ret;
+	u16 raw[2];
+	u16 *data;
+
+	ret = lmp92064_read_meas(priv, raw);
+	if (ret < 0)
+		goto done;
+
+	data = kmalloc(indio_dev->scan_bytes, GFP_KERNEL);
+	if (!data)
+		goto done;
+
+	for_each_set_bit(j, indio_dev->active_scan_mask, indio_dev->masklength)
+		data[i++] = raw[j];
+
+	iio_push_to_buffers_with_timestamp(indio_dev, data,
+					   iio_get_time_ns(indio_dev));
+
+	kfree(data);
+
+done:
+	iio_trigger_notify_done(indio_dev->trig);
+
+	return IRQ_HANDLED;
+}
+
 static int lmp92064_reset(struct lmp92064_adc_priv *priv,
 			  struct gpio_desc *gpio_reset)
 {
@@ -302,6 +351,11 @@  static int lmp92064_adc_probe(struct spi_device *spi)
 	indio_dev->num_channels = ARRAY_SIZE(lmp92064_adc_channels);
 	indio_dev->info = &lmp92064_adc_info;
 
+	ret = devm_iio_triggered_buffer_setup(dev, indio_dev, NULL,
+					      lmp92064_trigger_handler, NULL);
+	if (ret)
+		return dev_err_probe(dev, ret, "Failed to setup buffered read\n");
+
 	return devm_iio_device_register(dev, indio_dev);
 }