On Wed, 14 Jun 2023 09:55:36 +0200
Leonard Göhrs <l.goehrs@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx>
> ---
> 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
