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Mon, 20 Oct 2025 15:13:52 -0400 From: Marcelo Schmitt To: , , , CC: , , , , , , , , , , Subject: [PATCH v6 2/8] Docs: iio: ad4030: Add double PWM SPI offload doc Date: Mon, 20 Oct 2025 16:13:49 -0300 Message-ID: <9accfba376f997bc52293ad8fe151cbca98b0725.1760984107.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: 7ZrOBwhmsRvqsdBuIVuHfb6WBJXZbfIp X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMDE4MDAzNSBTYWx0ZWRfX0ujCNs2mU7sA keVfkiKo31VNyOYSRJHy1XfVGM7haOj/2p2epjWC2OxS57SpuYb29jMDPXAxPH1R14lFh5YpLcd rHwck/GcfBlzG89S4Q3p6Gh4Dbf0CgWBsuowJs0AINsEWc/tyMbXNbsZq2SDu/z3fx/KtNVr4vP /PfR2ahhJ0sN2y47iggyVqtygQLCsrY3IO64p496q9NFmB7oTzAHGlaSRkkdQ7PKx1KrE2TimfN 81qEa3eSgOPFuIl0p+uavlQ2DSlcYoSQbfVS9veKl27a8KeEkpEioO4pXAVB5DZE6LcEYuKvUoi cQDYmyIZvJJbaijplEEZj8UBhwSWwfLBEekm2iZRlplLCb6kdsHzsISdgwMlT5Xxn5jujW8fx6Z fhK8ubcvhpRYLdKTqjxgqMbScsr50w== X-Authority-Analysis: v=2.4 cv=KKtXzVFo c=1 sm=1 tr=0 ts=68f68a00 cx=c_pps a=PpDZqlmH/M8setHirZLBMw==:117 a=PpDZqlmH/M8setHirZLBMw==:17 a=x6icFKpwvdMA:10 a=VkNPw1HP01LnGYTKEx00:22 a=wI1k2SEZAAAA:8 a=IpJZQVW2AAAA:8 a=gAnH3GRIAAAA:8 a=Z7BqY8bEq__jAXHbdh4A:9 a=6HWbV-4b7c7AdzY24d_u:22 a=IawgGOuG5U0WyFbmm1f5:22 a=poXaRoVlC6wW9_mwW8W4:22 a=cPQSjfK2_nFv0Q5t_7PE:22 a=pHzHmUro8NiASowvMSCR:22 a=xoEH_sTeL_Rfw54TyV31:22 X-Proofpoint-GUID: 7ZrOBwhmsRvqsdBuIVuHfb6WBJXZbfIp X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.80.40 definitions=2025-10-20_05,2025-10-13_01,2025-03-28_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 adultscore=0 phishscore=0 lowpriorityscore=0 spamscore=0 priorityscore=1501 bulkscore=0 impostorscore=0 clxscore=1015 suspectscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510020000 definitions=main-2510180035 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