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From: Jonathan Cameron <jic23@kernel.org>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Lars-Peter Clausen <lars@metafoo.de>,
	linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Nuno Sa <Nuno.Sa@analog.com>
Subject: Re: [PATCH v2 05/16] iio: adc: max1027: Minimize the number of converted channels
Date: Sun, 5 Sep 2021 16:34:06 +0100	[thread overview]
Message-ID: <20210905163406.4d4d86a0@jic23-huawei> (raw)
In-Reply-To: <20210902211437.503623-6-miquel.raynal@bootlin.com>

On Thu,  2 Sep 2021 23:14:26 +0200
Miquel Raynal <miquel.raynal@bootlin.com> 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@bootlin.com>
> ---
>  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);
>  


  reply	other threads:[~2021-09-05 15:30 UTC|newest]

Thread overview: 33+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-02 21:14 [PATCH v2 00/16] Bring external triggers support to MAX1027-like ADCs Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 01/16] iio: adc: max1027: Fix style Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 02/16] iio: adc: max1027: Drop extra warning message Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 03/16] iio: adc: max1027: Drop useless debug messages Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 04/16] iio: adc: max1027: Avoid device managed allocators for DMA purposes Miquel Raynal
2021-09-05 15:26   ` Jonathan Cameron
2021-09-02 21:14 ` [PATCH v2 05/16] iio: adc: max1027: Minimize the number of converted channels Miquel Raynal
2021-09-05 15:34   ` Jonathan Cameron [this message]
2021-09-15  9:46     ` Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 06/16] iio: adc: max1027: Rename a helper Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 07/16] iio: adc: max1027: Create a helper to enable/disable the cnvst trigger Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 08/16] iio: adc: max1027: Simplify the _set_trigger_state() helper Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 09/16] iio: adc: max1027: Ensure a default cnvst trigger configuration Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 10/16] iio: adc: max1027: Create a helper to configure the channels to scan Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 11/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Miquel Raynal
2021-09-05 15:38   ` Jonathan Cameron
2021-09-02 21:14 ` [PATCH v2 12/16] iio: adc: max1027: Separate the IRQ handler from the read logic Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 13/16] iio: adc: max1027: Introduce an end of conversion helper Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 14/16] iio: adc: max1027: Don't just sleep when the EOC interrupt is available Miquel Raynal
2021-09-06  9:38   ` Sa, Nuno
2021-09-15  9:55     ` Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 15/16] iio: adc: max1027: Add support for external triggers Miquel Raynal
2021-09-05 16:10   ` Jonathan Cameron
2021-09-06  9:53     ` Sa, Nuno
2021-09-15 15:45       ` Miquel Raynal
2021-09-18 17:39         ` Jonathan Cameron
2021-09-20 10:47           ` Miquel Raynal
2021-09-15 10:18     ` Miquel Raynal
2021-09-18 17:13       ` Jonathan Cameron
2021-09-20  8:37         ` Miquel Raynal
2021-09-20 17:43           ` Jonathan Cameron
2021-09-21  8:11             ` Miquel Raynal
2021-09-02 21:14 ` [PATCH v2 16/16] iio: adc: max1027: Don't reject external triggers when there is no IRQ Miquel Raynal

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