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Fri, 6 Feb 2026 14:00:43 -0500 From: Marcelo Schmitt To: , , , CC: , , , , , , , , , , Subject: [PATCH v8 2/8] Docs: iio: ad4030: Add double PWM SPI offload doc Date: Fri, 6 Feb 2026 16:00:40 -0300 Message-ID: <0dfcdf2c2018b1174f2057f0c66e336b0b550bab.1770403407.git.marcelo.schmitt@analog.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: 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 X-ADIRuleOP-NewSCL: Rule Triggered X-Proofpoint-ORIG-GUID: 83HkkueDhrqSw8jeIoCEjm3emVODsmGW X-Proofpoint-GUID: 83HkkueDhrqSw8jeIoCEjm3emVODsmGW X-Authority-Analysis: v=2.4 cv=eqzSD4pX c=1 sm=1 tr=0 ts=69863a68 cx=c_pps a=3WNzaoukacrqR9RwcOSAdA==:117 a=3WNzaoukacrqR9RwcOSAdA==:17 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=wI1k2SEZAAAA:8 a=IpJZQVW2AAAA:8 a=gAnH3GRIAAAA:8 a=Z7BqY8bEq__jAXHbdh4A:9 a=qcg49hLlgF0N60+LroqrWnV/Vu4=:19 a=6HWbV-4b7c7AdzY24d_u:22 a=IawgGOuG5U0WyFbmm1f5:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjA2MDE0MCBTYWx0ZWRfX+VVpo2ADRAP0 tAKvPFG1KKoMspTgb5YqjRnTyhAKkfXZgyaCzxj/GE+GjP8C2jIx9KGMQg6E4oveXDpj6egguTj ZWDrCrIqiEEq87ETyovzfmBBLwu8PuH7WAZOCDaE5tkCPtpyO16TQpac861MvApzLt5NUARYqVI 135/BayLzbLhiVDMR3A62bOkIobLY7i6110qUxrA7R3flarFwzVGqGQGJxuFnQengQ4Uqtqme2t K7zhDpmtvaxHuwswyedq/eXsz18uOVKeCDzky8H8iTxjU8TDXznRRDW+YvvDZuaUZ/RNU+jYupp 579zInGZWzTim38ILCyR3hpNTBKtAeawbWl7nyyqSwGkvtWQ+uofeAGe64obn6t/+TowJ9UkJmc +cEmFQPSd28LlX+p0agRRKhEYxJu7sQnQJTFmlzO+fJ1nLur0AWAKKQnun1dnuICVi/ykm2Igts wd3lPMh5R+W5yPLWmpA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-06_05,2026-02-05_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 spamscore=0 malwarescore=0 clxscore=1015 phishscore=0 bulkscore=0 adultscore=0 impostorscore=0 suspectscore=0 priorityscore=1501 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602060140 Content-Type: text/plain; charset="utf-8" Document double PWM setup SPI offload wiring schema. Reviewed-by: David Lechner Signed-off-by: Marcelo Schmitt --- Documentation/iio/ad4030.rst | 39 ++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) diff --git a/Documentation/iio/ad4030.rst b/Documentation/iio/ad4030.rst index b57424b650a8..9caafa4148b0 100644 --- a/Documentation/iio/ad4030.rst +++ b/Documentation/iio/ad4030.rst @@ -92,6 +92,45 @@ Interleaved mode In this mode, both channels conversion results are bit interleaved one SDO= line. As such the wiring is the same as `One lane mode`_. =20 +SPI offload wiring +^^^^^^^^^^^^^^^^^^ + +.. code-block:: + + +-------------+ +-------------+ + | CNV |<-----+--| GPIO | + | | +--| PWM0 | + | | | | + | | +--| PWM1 | + | | | +-------------+ + | | +->| TRIGGER | + | CS |<--------| CS | + | | | | + | ADC | | SPI | + | | | | + | SDI |<--------| SDO | + | SDO |-------->| SDI | + | SCLK |<--------| SCLK | + +-------------+ +-------------+ + +In this mode, both the ``cnv-gpios`` and a ``pwms`` properties are require= d. +The ``pwms`` property specifies the PWM that is connected to the ADC CNV p= in. +The SPI offload will have a ``trigger-sources`` property to indicate the S= PI +offload (PWM) trigger source. For AD4030 and similar ADCs, there are two +possible data transfer zones for sample N. One of them (zone 1) starts aft= er the +data conversion for sample N is complete while the other one (zone 2) star= ts 9.8 +nanoseconds after the rising edge of CNV for sample N + 1. + +The configuration depicted in the above diagram is intended to perform data +transfer in zone 2. To achieve high sample rates while meeting ADC timing +requirements, an offset is added between the rising edges of PWM0 and PWM1= to +delay the SPI transfer until 9.8 nanoseconds after CNV rising edge. This +requires a specialized PWM controller that can provide such an offset. +The `AD4630-FMC HDL project`_, for example, can be configured to sample AD= 4030 +data during zone 2 data read window. + +.. _AD4630-FMC HDL project: https://analogdevicesinc.github.io/hdl/project= s/ad4630_fmc/index.html + SPI Clock mode -------------- =20 --=20 2.39.2