On Fri, 2023-07-07 at 08:36 +0200, 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@xxxxxxxxxxxxxx>
> ---
Reviewed-by: Nuno Sa <nuno.sa@xxxxxxxxxx>
> Changes v1->v2:
>
> - Remove superfluous .shift = 0 initialization in scan_type.
> - Replace kmalloc buffer allocation for every read with a stack
> allocated structure.
> A struct is used to ensure correct alignment of the timestamp field.
> See e.g. adc/rockchip_saradc.c for other users of the same pattern.
> - Use available_scan_masks and always push both voltage and current
> measurements to the buffer.
>
> Changes v2->v3:
>
> - Handle errors returned by lmp92064_read_meas() out-of-line via
> a goto err;
>
> Changes v3->v4:
>
> - 8-Byte align the 64 bit timestamp in the buffer structure
> and memset() the stack-allocated buffer to prevent leaking
> kernel memory to userspace. (Thanks to Nuno Sá)
> ---
> drivers/iio/adc/ti-lmp92064.c | 53 +++++++++++++++++++++++++++++++++++
> 1 file changed, 53 insertions(+)
>
> diff --git a/drivers/iio/adc/ti-lmp92064.c b/drivers/iio/adc/ti-lmp92064.c
> index c30ed824924f3..84ba5c4a0eea7 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 +94,12 @@ 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 = TI_LMP92064_CHAN_INC,
> + .scan_type = {
> + .sign = 'u',
> + .realbits = 12,
> + .storagebits = 16,
> + },
> .datasheet_name = "INC",
> },
> {
> @@ -98,8 +107,20 @@ 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 = TI_LMP92064_CHAN_INV,
> + .scan_type = {
> + .sign = 'u',
> + .realbits = 12,
> + .storagebits = 16,
> + },
> .datasheet_name = "INV",
> },
> + IIO_CHAN_SOFT_TIMESTAMP(2),
> +};
> +
> +static const unsigned long lmp92064_scan_masks[] = {
> + BIT(TI_LMP92064_CHAN_INC) | BIT(TI_LMP92064_CHAN_INV),
> + 0
> };
>
> static int lmp92064_read_meas(struct lmp92064_adc_priv *priv, u16 *res)
> @@ -171,6 +192,32 @@ 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);
> + struct {
> + u16 values[2];
> + int64_t timestamp __aligned(8);
> + } data;
> + int ret;
> +
> + memset(&data, 0, sizeof(data));
> +
> + ret = lmp92064_read_meas(priv, data.values);
> + if (ret)
> + goto err;
> +
> + iio_push_to_buffers_with_timestamp(indio_dev, &data,
> + iio_get_time_ns(indio_dev));
> +
> +err:
> + iio_trigger_notify_done(indio_dev->trig);
> +
> + return IRQ_HANDLED;
> +}
> +
> static int lmp92064_reset(struct lmp92064_adc_priv *priv,
> struct gpio_desc *gpio_reset)
> {
> @@ -301,6 +348,12 @@ static int lmp92064_adc_probe(struct spi_device *spi)
> indio_dev->channels = lmp92064_adc_channels;
> indio_dev->num_channels = ARRAY_SIZE(lmp92064_adc_channels);
> indio_dev->info = &lmp92064_adc_info;
> + indio_dev->available_scan_masks = lmp92064_scan_masks;
> +
> + 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: 6995e2de6891c724bfeb2db33d7b87775f913ad1
