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From: Miquel Raynal <miquel.raynal@bootlin.com>
To: Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	Nuno Sa <Nuno.Sa@analog.com>,
	Miquel Raynal <miquel.raynal@bootlin.com>
Subject: [PATCH v4 04/16] iio: adc: max1027: Minimize the number of converted channels
Date: Tue, 21 Sep 2021 13:53:56 +0200	[thread overview]
Message-ID: <20210921115408.66711-5-miquel.raynal@bootlin.com> (raw)
In-Reply-To: <20210921115408.66711-1-miquel.raynal@bootlin.com>

Provide a list of ->available_scan_masks which match the device's
capabilities. Basically, these devices are 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.

Provide a comment in the code explaining this logic.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
---
 drivers/iio/adc/max1027.c | 60 ++++++++++++++++++++++++++++++++++-----
 1 file changed, 53 insertions(+), 7 deletions(-)

diff --git a/drivers/iio/adc/max1027.c b/drivers/iio/adc/max1027.c
index f27044324141..7c1c76673be2 100644
--- a/drivers/iio/adc/max1027.c
+++ b/drivers/iio/adc/max1027.c
@@ -172,18 +172,53 @@ static const struct iio_chan_spec max1231_channels[] = {
 	MAX1X31_CHANNELS(12),
 };
 
+/*
+ * These devices are 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. Based on the below
+ * ->available_scan_masks, the core will select the most appropriate
+ * ->active_scan_mask and the "minimum" number of channels will be
+ * scanned and pushed to the buffers.
+ *
+ * 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.
+ */
+#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 +403,15 @@ 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 +432,14 @@ 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);
 
-- 
2.27.0


  parent reply	other threads:[~2021-09-21 11:54 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-21 11:53 [PATCH v4 00/16] Bring external triggers support to MAX1027-like ADCs Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 01/16] iio: adc: max1027: Fix style Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 02/16] iio: adc: max1027: Drop extra warning message Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 03/16] iio: adc: max1027: Drop useless debug messages Miquel Raynal
2021-09-21 11:53 ` Miquel Raynal [this message]
2021-09-21 11:53 ` [PATCH v4 05/16] iio: adc: max1027: Rename a helper Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 06/16] iio: adc: max1027: Create a helper to enable/disable the cnvst trigger Miquel Raynal
2021-09-21 11:53 ` [PATCH v4 07/16] iio: adc: max1027: Simplify the _set_trigger_state() helper Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 08/16] iio: adc: max1027: Ensure a default cnvst trigger configuration Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 09/16] iio: adc: max1027: Create a helper to configure the channels to scan Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 10/16] iio: adc: max1027: Prevent single channel accesses during buffer reads Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 11/16] iio: adc: max1027: Separate the IRQ handler from the read logic Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 12/16] iio: adc: max1027: Introduce an end of conversion helper Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 13/16] iio: adc: max1027: Stop requesting a threaded IRQ Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 14/16] iio: adc: max1027: Use the EOC IRQ when populated for single reads Miquel Raynal
2021-09-26 14:36   ` Jonathan Cameron
2021-09-27 14:30     ` Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 15/16] iio: adc: max1027: Allow all kind of triggers to be used Miquel Raynal
2021-09-21 11:54 ` [PATCH v4 16/16] iio: adc: max1027: Don't reject external triggers when there is no IRQ Miquel Raynal
2021-09-26 14:38 ` [PATCH v4 00/16] Bring external triggers support to MAX1027-like ADCs Jonathan Cameron

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