On Thu, 2 Sep 2021 23:14:26 +0200
Miquel Raynal <miquel.raynal@xxxxxxxxxxx> wrote:
> Provide a list of ->available_scan_masks which match the device's
> capabilities. Basically, the devices is able to scan from 0 to N, N
> being the highest voltage channel requested by the user. The temperature
> can be included or not, but cannot be retrieved alone.
>
> The consequence is, instead of reading and pushing to the IIO buffers
> all channels each time, the "minimum" number of channels will be scanned
> and pushed based on the ->active_scan_mask.
>
> For example, if the user wants channels 1, 4 and 5, all channels from
> 0 to 5 will be scanned and pushed to the IIO buffers. The core will then
> filter out the unneeded samples based on the ->active_scan_mask that has
> been selected and only channels 1, 4 and 5 will be available to the user
> in the shared buffer.
This explanation is excellent. If you are respinning it would be great
to have the essence of it as a comment alongside the code.
The bit about temp in particular was something I'd missed.
Nice optimization in general.
Jonathan
>
> Signed-off-by: Miquel Raynal <miquel.raynal@xxxxxxxxxxx>
> ---
> drivers/iio/adc/max1027.c | 46 +++++++++++++++++++++++++++++++++------
> 1 file changed, 39 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index 1167d50c1d67..3c41d2c0ed2a 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -172,18 +172,39 @@ static const struct iio_chan_spec max1231_channels[] = {
> MAX1X31_CHANNELS(12),
> };
>
> +#define MAX1X27_SCAN_MASK_TEMP BIT(0)
> +
> +#define MAX1X27_SCAN_MASKS(temp) \
> + GENMASK(1, 1 - (temp)), GENMASK(2, 1 - (temp)), \
> + GENMASK(3, 1 - (temp)), GENMASK(4, 1 - (temp)), \
> + GENMASK(5, 1 - (temp)), GENMASK(6, 1 - (temp)), \
> + GENMASK(7, 1 - (temp)), GENMASK(8, 1 - (temp))
> +
> +#define MAX1X29_SCAN_MASKS(temp) \
> + MAX1X27_SCAN_MASKS(temp), \
> + GENMASK(9, 1 - (temp)), GENMASK(10, 1 - (temp)), \
> + GENMASK(11, 1 - (temp)), GENMASK(12, 1 - (temp))
> +
> +#define MAX1X31_SCAN_MASKS(temp) \
> + MAX1X29_SCAN_MASKS(temp), \
> + GENMASK(13, 1 - (temp)), GENMASK(14, 1 - (temp)), \
> + GENMASK(15, 1 - (temp)), GENMASK(16, 1 - (temp))
> +
> static const unsigned long max1027_available_scan_masks[] = {
> - 0x000001ff,
> + MAX1X27_SCAN_MASKS(0),
> + MAX1X27_SCAN_MASKS(1),
> 0x00000000,
> };
>
> static const unsigned long max1029_available_scan_masks[] = {
> - 0x00001fff,
> + MAX1X29_SCAN_MASKS(0),
> + MAX1X29_SCAN_MASKS(1),
> 0x00000000,
> };
>
> static const unsigned long max1031_available_scan_masks[] = {
> - 0x0001ffff,
> + MAX1X31_SCAN_MASKS(0),
> + MAX1X31_SCAN_MASKS(1),
> 0x00000000,
> };
>
> @@ -368,9 +389,15 @@ static int max1027_set_trigger_state(struct iio_trigger *trig, bool state)
> if (ret < 0)
> return ret;
>
> - /* Scan from 0 to max */
> - st->reg = MAX1027_CONV_REG | MAX1027_CHAN(0) |
> - MAX1027_SCAN_N_M | MAX1027_TEMP;
> + /*
> + * Scan from chan 0 to the highest requested channel.
> + * Include temperature on demand.
> + */
> + st->reg = MAX1027_CONV_REG | MAX1027_SCAN_0_N;
> + st->reg |= MAX1027_CHAN(fls(*indio_dev->active_scan_mask) - 2);
> + if (*indio_dev->active_scan_mask & MAX1X27_SCAN_MASK_TEMP)
> + st->reg |= MAX1027_TEMP;
> +
> ret = spi_write(st->spi, &st->reg, 1);
> if (ret < 0)
> return ret;
> @@ -391,9 +418,14 @@ static irqreturn_t max1027_trigger_handler(int irq, void *private)
> struct iio_poll_func *pf = private;
> struct iio_dev *indio_dev = pf->indio_dev;
> struct max1027_state *st = iio_priv(indio_dev);
> + unsigned int scanned_chans;
> +
> + scanned_chans = fls(*indio_dev->active_scan_mask) - 1;
> + if (*indio_dev->active_scan_mask & MAX1X27_SCAN_MASK_TEMP)
> + scanned_chans++;
>
> /* fill buffer with all channel */
> - spi_read(st->spi, st->buffer, indio_dev->masklength * 2);
> + spi_read(st->spi, st->buffer, scanned_chans * 2);
>
> iio_push_to_buffers(indio_dev, st->buffer);
>
