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Sun, 08 Mar 2026 11:29:17 -0700 (PDT) From: Archit Anant To: jic23@kernel.org, dlechner@baylibre.com Cc: lars@metafoo.de, Michael.Hennerich@analog.com, nuno.sa@analog.com, andy@kernel.org, linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org, Archit Anant Subject: [PATCH v4 2/4] iio: adc: ad799x: cache regulator voltage during probe Date: Sun, 8 Mar 2026 23:58:09 +0530 Message-Id: <20260308182811.33471-3-architanant5@gmail.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20260308182811.33471-1-architanant5@gmail.com> References: <20260308182811.33471-1-architanant5@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Reading the regulator voltage via regulator_get_voltage() can be a slow operation. Since the reference voltage for this ADC is not expected to change at runtime, it is inefficient to query the regulator API every time userspace reads the IIO_CHAN_INFO_SCALE attribute. Determine the active reference voltage (either VREF or VCC) during probe() and cache it in a single variable in the state structure. This improves the performance of ad799x_read_raw(), removes the dependency on the regulator pointers during fast-path reads, and allows the removal of a redundant negative-value check. Suggested-by: Jonathan Cameron Suggested-by: David Lechner Signed-off-by: Archit Anant --- drivers/iio/adc/ad799x.c | 21 +++++++++++++-------- 1 file changed, 13 insertions(+), 8 deletions(-) diff --git a/drivers/iio/adc/ad799x.c b/drivers/iio/adc/ad799x.c index c1a7fa37706f..28f1901698a6 100644 --- a/drivers/iio/adc/ad799x.c +++ b/drivers/iio/adc/ad799x.c @@ -135,6 +135,9 @@ struct ad799x_state { u16 config; =20 unsigned int transfer_size; + + int vref_uV; + IIO_DECLARE_BUFFER_WITH_TS(__be16, rx_buf, AD799X_MAX_CHANNELS); }; =20 @@ -302,14 +305,7 @@ static int ad799x_read_raw(struct iio_dev *indio_dev, GENMASK(chan->scan_type.realbits - 1, 0); return IIO_VAL_INT; case IIO_CHAN_INFO_SCALE: - if (st->vref) - ret =3D regulator_get_voltage(st->vref); - else - ret =3D regulator_get_voltage(st->reg); - - if (ret < 0) - return ret; - *val =3D ret / 1000; + *val =3D st->vref_uV / 1000; *val2 =3D chan->scan_type.realbits; return IIO_VAL_FRACTIONAL_LOG2; } @@ -809,6 +805,10 @@ static int ad799x_probe(struct i2c_client *client) ret =3D regulator_enable(st->reg); if (ret) return ret; + ret =3D regulator_get_voltage(st->reg); + if (ret < 0) + goto error_disable_reg; + st->vref_uV =3D ret; =20 /* check if an external reference is supplied */ if (chip_info->has_vref) { @@ -827,6 +827,11 @@ static int ad799x_probe(struct i2c_client *client) ret =3D regulator_enable(st->vref); if (ret) goto error_disable_reg; + + ret =3D regulator_get_voltage(st->vref); + if (ret < 0) + goto error_disable_vref; + st->vref_uV =3D ret; } } =20 --=20 2.39.5