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From: "Sa, Nuno" <Nuno.Sa@analog.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>,
	Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	"linux-iio@vger.kernel.org" <linux-iio@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 03/16] iio: adc: max1027: Push only the requested samples
Date: Fri, 20 Aug 2021 07:10:48 +0000	[thread overview]
Message-ID: <SJ0PR03MB6359415E120CFD3EFAF417F599C19@SJ0PR03MB6359.namprd03.prod.outlook.com> (raw)
In-Reply-To: <20210818111139.330636-4-miquel.raynal@bootlin.com>



> -----Original Message-----
> From: Miquel Raynal <miquel.raynal@bootlin.com>
> Sent: Wednesday, August 18, 2021 1:11 PM
> To: Jonathan Cameron <jic23@kernel.org>; Lars-Peter Clausen
> <lars@metafoo.de>
> Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>; linux-
> iio@vger.kernel.org; linux-kernel@vger.kernel.org; Miquel Raynal
> <miquel.raynal@bootlin.com>
> Subject: [PATCH 03/16] iio: adc: max1027: Push only the requested
> samples
> 
> [External]
> 
> When a triggered scan occurs, the identity of the desired channels is
> known in indio_dev->active_scan_mask. Instead of reading and
> pushing to
> the IIO buffers all channels each time, scan the minimum amount of
> channels (0 to maximum requested chan, to be exact) and only
> provide the
> samples requested by the user.
> 
> For example, if the user wants channels 1, 4 and 5, all channels from
> 0 to 5 will be scanned but only the desired channels will be pushed to
> the IIO buffers.
> 
> Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> ---
>  drivers/iio/adc/max1027.c | 25 +++++++++++++++++++++----
>  1 file changed, 21 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
> index b753658bb41e..8ab660f596b5 100644
> --- a/drivers/iio/adc/max1027.c
> +++ b/drivers/iio/adc/max1027.c
> @@ -360,6 +360,9 @@ static int max1027_set_trigger_state(struct
> iio_trigger *trig, bool state)
>  	struct max1027_state *st = iio_priv(indio_dev);
>  	int ret;
> 
> +	if (bitmap_empty(indio_dev->active_scan_mask, indio_dev-
> >masklength))
> +		return -EINVAL;
> +

I'm not sure this can actually happen. If you try to enable the buffer
with no scan element, it should give you an error before you reach
this point...

>  	if (state) {
>  		/* Start acquisition on cnvst */
>  		st->reg = MAX1027_SETUP_REG |
> MAX1027_CKS_MODE0 |
> @@ -368,9 +371,12 @@ 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 0 to the highest requested channel. The
> temperature
> +		 * could be avoided but it simplifies a bit the logic.
> +		 */
> +		st->reg = MAX1027_CONV_REG |
> MAX1027_SCAN_0_N | MAX1027_TEMP;
> +		st->reg |= MAX1027_CHAN(fls(*indio_dev-
> >active_scan_mask) - 2);
>  		ret = spi_write(st->spi, &st->reg, 1);
>  		if (ret < 0)
>  			return ret;
> @@ -391,11 +397,22 @@ 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 = fls(*indio_dev-
> >active_scan_mask);
> +	u16 *buf = st->buffer;

I think sparse will complain here. buffer is a __be16 restricted
type so you should not mix those... 
> +	unsigned int bit;
> 
>  	pr_debug("%s(irq=%d, private=0x%p)\n", __func__, irq,
> private);
> 
>  	/* fill buffer with all channel */
> -	spi_read(st->spi, st->buffer, indio_dev->masklength * 2);
> +	spi_read(st->spi, st->buffer, scanned_chans * 2);
> +
> +	/* Only keep the channels selected by the user */
> +	for_each_set_bit(bit, indio_dev->active_scan_mask,
> +			 indio_dev->masklength) {
> +		if (buf[0] != st->buffer[bit])
> +			buf[0] = st->buffer[bit];

Since we are here, when looking into the driver, I realized
that st->buffer is not DMA safe. In IIO, we kind of want to enforce
that all buffers that are passed to spi/i2c buses are safe... Maybe
this is something you can include in your series.

- Nuno Sá

 > +		buf++;
> +	}
> 
>  	iio_push_to_buffers(indio_dev, st->buffer);
> 
> --
> 2.27.0


  reply	other threads:[~2021-08-20  7:11 UTC|newest]

Thread overview: 71+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-18 11:11 [PATCH 00/16] Bring software triggers support to MAX1027-like ADCs Miquel Raynal
2021-08-18 11:11 ` [PATCH 01/16] iio: adc: max1027: Fix wrong shift with 12-bit devices Miquel Raynal
2021-08-20  7:02   ` Sa, Nuno
2021-08-30  9:57     ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 02/16] iio: adc: max1027: Fix the number of max1X31 channels Miquel Raynal
2021-08-20  7:03   ` Sa, Nuno
2021-08-30 10:00     ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 03/16] iio: adc: max1027: Push only the requested samples Miquel Raynal
2021-08-20  7:10   ` Sa, Nuno [this message]
2021-08-30 10:07     ` Jonathan Cameron
2021-08-30 10:49       ` Sa, Nuno
2021-08-30 14:29         ` Jonathan Cameron
2021-08-30 15:02           ` Sa, Nuno
2021-09-01  8:12             ` Miquel Raynal
2021-09-04 14:06               ` Jonathan Cameron
2021-09-06  8:59               ` Sa, Nuno
2021-09-06 16:56                 ` Jonathan Cameron
2021-09-06 17:34                   ` Miquel Raynal
2021-08-30 10:06   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 04/16] iio: adc: max1027: Lower conversion time Miquel Raynal
2021-08-20  7:12   ` Sa, Nuno
2021-08-30 10:10   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 05/16] iio: adc: max1027: Drop extra warning message Miquel Raynal
2021-08-20  7:12   ` Sa, Nuno
2021-08-30 10:12   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 06/16] iio: adc: max1027: Rename a helper Miquel Raynal
2021-08-20  7:13   ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 07/16] iio: adc: max1027: Create a helper to configure the trigger Miquel Raynal
2021-08-20  7:16   ` Sa, Nuno
2021-08-30 10:16   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 08/16] iio: adc: max1027: Explain better how the trigger state gets changed Miquel Raynal
2021-08-20  7:17   ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 09/16] iio: adc: max1027: Create a helper to configure the channels to scan Miquel Raynal
2021-08-20  7:18   ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 10/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Miquel Raynal
2021-08-20  7:20   ` Sa, Nuno
2021-08-20  7:30     ` Sa, Nuno
2021-08-30 10:20       ` Jonathan Cameron
2021-09-02  8:56         ` Miquel Raynal
2021-08-18 11:11 ` [PATCH 11/16] iio: adc: max1027: Separate the IRQ handler from the read logic Miquel Raynal
2021-08-20  7:23   ` Sa, Nuno
2021-09-02  8:55     ` Miquel Raynal
2021-09-04 14:08       ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 12/16] iio: adc: max1027: Introduce an end of conversion helper Miquel Raynal
2021-08-20  7:28   ` Sa, Nuno
2021-09-02  9:26     ` Miquel Raynal
2021-08-30 10:34   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 13/16] iio: adc: max1027: Prepare re-using the EOC interrupt Miquel Raynal
2021-08-20  7:31   ` Sa, Nuno
2021-08-30 10:30   ` Jonathan Cameron
2021-08-30 10:47   ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 14/16] iio: adc: max1027: Consolidate the end of conversion helper Miquel Raynal
2021-08-20  7:45   ` Sa, Nuno
2021-08-30 10:37   ` Jonathan Cameron
2021-08-30 12:44     ` Sa, Nuno
2021-08-30 14:32       ` Jonathan Cameron
2021-09-02 15:12       ` Miquel Raynal
2021-09-03 14:28         ` Sa, Nuno
2021-09-03 14:46           ` Miquel Raynal
2021-09-05  9:41             ` Jonathan Cameron
2021-09-06  9:12               ` Sa, Nuno
2021-09-06  9:30                 ` Sa, Nuno
2021-08-18 11:11 ` [PATCH 15/16] iio: adc: max1027: Support software triggers Miquel Raynal
2021-08-20  7:58   ` Sa, Nuno
2021-09-02 12:25     ` Miquel Raynal
2021-09-03 14:20       ` Sa, Nuno
2021-08-30 10:50   ` Jonathan Cameron
2021-09-02 15:21     ` Miquel Raynal
2021-09-05  9:43       ` Jonathan Cameron
2021-08-18 11:11 ` [PATCH 16/16] iio: adc: max1027: Enable software triggers to be used without IRQ Miquel Raynal
2021-08-30 10:54   ` Jonathan Cameron

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