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Fri, 07 Aug 2026 20:58:59 -0700 (PDT) From: Kurt Borja Date: Fri, 07 Aug 2026 22:58:27 -0500 Subject: [PATCH v3 5/9] iio: adc: ti-ads1262: support input chopping Precedence: bulk X-Mailing-List: devicetree@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260807-ads126x-v3-5-f89925d72792@gmail.com> References: <20260807-ads126x-v3-0-f89925d72792@gmail.com> In-Reply-To: <20260807-ads126x-v3-0-f89925d72792@gmail.com> To: Kurt Borja , Jonathan Cameron , Rob Herring , Krzysztof Kozlowski , Conor Dooley , Linus Walleij , Bartosz Golaszewski , David Lechner Cc: =?utf-8?q?Nuno_S=C3=A1?= , Andy Shevchenko , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-gpio@vger.kernel.org, Jonathan Cameron X-Mailer: b4 0.15.2 X-Developer-Signature: v=1; a=openpgp-sha256; l=3294; i=kuurtb@gmail.com; h=from:subject:message-id; bh=VvzU2b+Z5pKj30/fjUw7xXFFO/Jtm5Yb6ds+h+Vgx40=; b=owGbwMvMwCUmluBs8WX+lTTG02pJDFllKysyqn8/NFS6ZbqsfsaL4rdHZLQWxn/pfn/dvP8Au 0tbTJVbRykLgxgXg6yYIkt7wqJvj6Ly3vodCL0PM4eVCWQIAxenAEzER5/hn+2l2hqFlkZ3vb+T tUr1I9kb1u5pu6fIz8rVuzf0r5oiD8P/UlXBhHt8e5asWiD8+/Q+1y3bY5n7f098uehJppiE+YN gbgA= X-Developer-Key: i=kuurtb@gmail.com; a=openpgp; fpr=54D3BE170AEF777983C3C63B57E3B6585920A69A Enable per-channel input chopping via the "input-chopping" property. As the device withholds the first conversion in chop mode, single reads are taken in CONTINUOUS run mode with a brief start/stop pulse, as recommended by the datasheet (Section 9.4.1.2). Signed-off-by: Kurt Borja --- drivers/iio/adc/ti-ads1262.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff --git a/drivers/iio/adc/ti-ads1262.c b/drivers/iio/adc/ti-ads1262.c index 360ce01a5871..e2659941e1af 100644 --- a/drivers/iio/adc/ti-ads1262.c +++ b/drivers/iio/adc/ti-ads1262.c @@ -210,6 +210,7 @@ struct ads1262_channel { u8 ref_n; bool ref_reversal; bool is_resistance; + bool input_chop; int offset; int scales[6][2]; size_t num_scales; @@ -374,7 +375,7 @@ static int ads1262_dev_stop(struct ads1262 *st) return ret; } -static int ads1262_dev_start_one(struct ads1262 *st) +static int ads1262_dev_start_one(struct ads1262 *st, u8 runmode) { int ret; @@ -382,7 +383,7 @@ static int ads1262_dev_start_one(struct ads1262 *st) if (ret) return ret; - if (st->start_gpiod) { + if (runmode == ADS1262_RUNMODE_CONTINUOUS || st->start_gpiod) { /* * The START pulse timing requirement is 4 clock cycles, at the * minimum clock rate this is 4 microseconds. @@ -431,8 +432,10 @@ static int ads1262_channel_enable(struct ads1262 *st, guard(mutex)(&st->xfer_lock); guard(mutex)(&st->chan_lock); - val = FIELD_PREP(ADS1262_MODE0_REFREV_MASK, chan->ref_reversal); + val = FIELD_PREP(ADS1262_MODE0_INPUT_CHOP_MASK, chan->input_chop) | + FIELD_PREP(ADS1262_MODE0_REFREV_MASK, chan->ref_reversal); ret = regmap_update_bits(st->regmap, ADS1262_MODE0_REG, + ADS1262_MODE0_INPUT_CHOP_MASK | ADS1262_MODE0_REFREV_MASK, val); if (ret) return ret; @@ -473,13 +476,26 @@ static int ads1262_channel_read(struct iio_dev *indio_dev, const struct iio_chan_spec *spec, __be32 *val) { struct ads1262 *st = iio_priv(indio_dev); + struct ads1262_channel *chan = &st->channels[spec->scan_index]; + u8 runmode; int ret; IIO_DEV_ACQUIRE_DIRECT_MODE(indio_dev, claim); if (IIO_DEV_ACQUIRE_FAILED(claim)) return -EBUSY; - ret = ads1262_set_runmode(st, ADS1262_RUNMODE_PULSE); + /* + * When a channel has chop mode or IDAC rotation mode, the first + * conversion is always withheld so the datasheet suggests using the + * CONTINUOUS mode and briefly starting and stopping conversions to + * achieve the same effect (Section 9.4.1.2). + */ + if (chan->input_chop) + runmode = ADS1262_RUNMODE_CONTINUOUS; + else + runmode = ADS1262_RUNMODE_PULSE; + + ret = ads1262_set_runmode(st, runmode); if (ret) return ret; @@ -489,7 +505,7 @@ static int ads1262_channel_read(struct iio_dev *indio_dev, reinit_completion(&st->drdy); - ret = ads1262_dev_start_one(st); + ret = ads1262_dev_start_one(st, runmode); if (ret) return ret; @@ -1134,6 +1150,7 @@ static int ads1262_parse_channel_node(struct ads1262 *st, } } + chan->input_chop = fwnode_property_read_bool(node, "input-chopping"); chan->ref_reversal = fwnode_property_read_bool(node, "ti,reference-reversal"); return 0; -- 2.55.0