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Wed, 04 Mar 2026 03:40:13 -0800 (PST) Message-ID: <7888782857fca26d6562c5cf1807fc7488c9dde8.camel@gmail.com> Subject: Re: [PATCH v2] iio: adc: xilinx-xadc: Fix sequencer mode in postdisable for dual mux From: Nuno =?ISO-8859-1?Q?S=E1?= To: Christofer Jonason , jic23@kernel.org Cc: lars@metafoo.de, dlechner@baylibre.com, nuno.sa@analog.com, andy@kernel.org, michal.simek@amd.com, victor.jonsson@guidelinegeo.com, linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Date: Wed, 04 Mar 2026 11:40:58 +0000 In-Reply-To: <20260304090727.1800289-1-christofer.jonason@guidelinegeo.com> References: <20260304090727.1800289-1-christofer.jonason@guidelinegeo.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Wed, 2026-03-04 at 10:07 +0100, Christofer Jonason wrote: > xadc_postdisable() unconditionally sets the sequencer to continuous > mode. For dual external multiplexer configurations this is incorrect: > simultaneous sampling mode is required so that ADC-A samples through > the mux on VAUX[0-7] while ADC-B simultaneously samples through the > mux on VAUX[8-15]. In continuous mode only ADC-A is active, so > VAUX[8-15] channels return incorrect data. >=20 > Since postdisable is also called from xadc_probe() to set the initial > idle state, the wrong sequencer mode is active from the moment the > driver loads. >=20 > The preenable path already uses xadc_get_seq_mode() which returns > SIMULTANEOUS for dual mux. Fix postdisable to do the same. >=20 > Fixes: bdc8cda1d010 ("iio:adc: Add Xilinx XADC driver") > Cc: stable@vger.kernel.org > Signed-off-by: Christofer Jonason > --- >From a code standpoint: Reviewed-by: Nuno S=C3=A1 > Changes in v2: > =C2=A0 - Align continuation line to opening parenthesis (Andy) > =C2=A0drivers/iio/adc/xilinx-xadc-core.c | 11 +++++++++-- > =C2=A01 file changed, 9 insertions(+), 2 deletions(-) >=20 > diff --git a/drivers/iio/adc/xilinx-xadc-core.c b/drivers/iio/adc/xilinx-= xadc-core.c > index e257c1b94..3980dfacb 100644 > --- a/drivers/iio/adc/xilinx-xadc-core.c > +++ b/drivers/iio/adc/xilinx-xadc-core.c > @@ -817,6 +817,7 @@ static int xadc_postdisable(struct iio_dev *indio_dev= ) > =C2=A0{ > =C2=A0 struct xadc *xadc =3D iio_priv(indio_dev); > =C2=A0 unsigned long scan_mask; > + int seq_mode; > =C2=A0 int ret; > =C2=A0 int i; > =C2=A0 > @@ -824,6 +825,12 @@ static int xadc_postdisable(struct iio_dev *indio_de= v) > =C2=A0 for (i =3D 0; i < indio_dev->num_channels; i++) > =C2=A0 scan_mask |=3D BIT(indio_dev->channels[i].scan_index); > =C2=A0 > + /* > + * Use the correct sequencer mode for the idle state: simultaneous > + * mode for dual external mux configurations, continuous otherwise. > + */ > + seq_mode =3D xadc_get_seq_mode(xadc, scan_mask); > + > =C2=A0 /* Enable all channels and calibration */ > =C2=A0 ret =3D xadc_write_adc_reg(xadc, XADC_REG_SEQ(0), scan_mask & 0xff= ff); > =C2=A0 if (ret) > @@ -834,11 +841,11 @@ static int xadc_postdisable(struct iio_dev *indio_d= ev) > =C2=A0 return ret; > =C2=A0 > =C2=A0 ret =3D xadc_update_adc_reg(xadc, XADC_REG_CONF1, XADC_CONF1_SEQ_M= ASK, > - XADC_CONF1_SEQ_CONTINUOUS); > + =C2=A0 seq_mode); > =C2=A0 if (ret) > =C2=A0 return ret; > =C2=A0 > - return xadc_power_adc_b(xadc, XADC_CONF1_SEQ_CONTINUOUS); > + return xadc_power_adc_b(xadc, seq_mode); > =C2=A0} > =C2=A0 > =C2=A0static int xadc_preenable(struct iio_dev *indio_dev)