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([2001:818:ea56:d000:94c4:fb0e:28f:2a8d]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46fb32a84edsm39166195e9.4.2025.10.10.12.45.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 10 Oct 2025 12:45:05 -0700 (PDT) Message-ID: <755d4fcea043d62ba6ac44c483f70c0a08b5e41e.camel@gmail.com> Subject: Re: [PATCH v4 6/8] iio: adc: ad4030: Add SPI offload support From: Nuno =?ISO-8859-1?Q?S=E1?= To: David Lechner , Marcelo Schmitt , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-pwm@vger.kernel.org, linux-spi@vger.kernel.org, linux-kernel@vger.kernel.org Cc: jic23@kernel.org, ukleinek@kernel.org, michael.hennerich@analog.com, nuno.sa@analog.com, eblanc@baylibre.com, andy@kernel.org, robh@kernel.org, krzk+dt@kernel.org, conor+dt@kernel.org, corbet@lwn.net, marcelo.schmitt1@gmail.com, Trevor Gamblin , Axel Haslam Date: Fri, 10 Oct 2025 19:46:01 +0100 In-Reply-To: <576b582e-7388-4ee4-9a4c-4f7e04fc3fda@baylibre.com> References: <2bde211f1bc730ee147c9540b88339a93b2983e6.1759929814.git.marcelo.schmitt@analog.com> <576b582e-7388-4ee4-9a4c-4f7e04fc3fda@baylibre.com> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.56.2 (3.56.2-2.fc42) Precedence: bulk X-Mailing-List: linux-spi@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Fri, 2025-10-10 at 11:18 -0500, David Lechner wrote: > On 10/10/25 6:19 AM, Nuno S=C3=A1 wrote: > > On Wed, 2025-10-08 at 10:51 -0300, Marcelo Schmitt wrote: > > > AD4030 and similar ADCs can capture data at sample rates up to 2 mega > > > samples per second (MSPS). Not all SPI controllers are able to achiev= e such > > > high throughputs and even when the controller is fast enough to run > > > transfers at the required speed, it may be costly to the CPU to handl= e > > > transfer data at such high sample rates. Add SPI offload support for = AD4030 > > > and similar ADCs to enable data capture at maximum sample rates. > > >=20 > > > Co-developed-by: Trevor Gamblin > > > Signed-off-by: Trevor Gamblin > > > Co-developed-by: Axel Haslam > > > Signed-off-by: Axel Haslam > > > Signed-off-by: Marcelo Schmitt > > > --- > > > Change log v3 -> v4 > > > - Applied code adjustments suggested to SPI offload patch. > > > - Only select SPI_OFFLOAD_TRIGGER_PWM if (SPI_OFFLOAD && PWM). > > >=20 > > > =C2=A0drivers/iio/adc/Kconfig=C2=A0 |=C2=A0=C2=A0 3 + > > > =C2=A0drivers/iio/adc/ad4030.c | 504 ++++++++++++++++++++++++++++++++= +++---- > > > =C2=A02 files changed, 465 insertions(+), 42 deletions(-) > > >=20 > > > diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig > > > index 58a14e6833f6..1ed091b6731a 100644 > > > --- a/drivers/iio/adc/Kconfig > > > +++ b/drivers/iio/adc/Kconfig > > > @@ -62,7 +62,10 @@ config AD4030 > > > =C2=A0 depends on GPIOLIB > > > =C2=A0 select REGMAP > > > =C2=A0 select IIO_BUFFER > > > + select IIO_BUFFER_DMA > > > + select IIO_BUFFER_DMAENGINE > > > =C2=A0 select IIO_TRIGGERED_BUFFER > > > + select SPI_OFFLOAD_TRIGGER_PWM if (SPI_OFFLOAD && PWM) > >=20 > > Two things as I mentioned in [1]: > >=20 > > 1) Wouldn't 'imply SPI_OFFLOAD_TRIGGER_PWM' accomplish the same? > > 2) Don't we also need stubs for spi/offload/consumer.h? >=20 > It doesn't hurt to enable SPI offload support even if no controller > supports it, so I would prefer that drivers that use it just select > SPI_OFFLOAD. It does not hurt for sure. I just don't love enabling code when the feature= is optional. For things like GPIO it not does not matter much because it's mos= t likely always enabled anyways. But, fair enough! I don't feel strong about this at all and if we wanted to= be picky then we would also have to take into account that IIO_BUFFER_DMA and IIO_BUFFER_DMAENGINE also depend on SPI_OFFLOAD being present and we just s= elect those. - Nuno S=C3=A1 >=20 > >=20 > > [1]: > > https://lore.kernel.org/linux-pwm/2e82eaf275b5c8df768c8b842167c3562991e= 50c.camel@gmail.com/T/#t > > - Nuno S=C3=A1 > > =C2=A0