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Fri, 17 Oct 2025 04:34:33 -0700 (PDT) Date: Fri, 17 Oct 2025 08:35:38 -0300 From: Marcelo Schmitt To: David Lechner Cc: Marcelo Schmitt , linux-iio@vger.kernel.org, devicetree@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, jic23@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, Trevor Gamblin , Axel Haslam Subject: Re: [PATCH v5 5/7] iio: adc: ad4030: Add SPI offload support Message-ID: References: Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On 10/16, David Lechner wrote: > On 10/14/25 5:22 PM, 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 achieve 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 handle > > transfer data at such high sample rates. Add SPI offload support for AD4030 > > and similar ADCs to enable data capture at maximum sample rates. > > > > 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 v4 -> v5 > > - Made Kconfig entry depend on PWM and select other features. > > - Reused ad4030_exit_config_mode() in ad4030_offload_buffer_postenable(). > > - Dropped common-mode voltage support on SPI offload setup. > > Curious why you chose this. I guess it will be fine to add it later > if anyone ever actually needs it. > I had coded that in a way I think would work for the dual channel devices, but it didn't really work for single-channel adaq4216. And yes, if anyone asks for offload with common-mode data, we shall probably be able to it that later. > > - Adjusted offload trigger period calculation. > > - No longer setting data frame mode from ad4030_set_avg_frame_len(). > > - Rearranged code to reduce patch diff. > > > > drivers/iio/adc/Kconfig | 5 + > > drivers/iio/adc/ad4030.c | 425 +++++++++++++++++++++++++++++++++++++-- > > 2 files changed, 416 insertions(+), 14 deletions(-) > > > > ... > > > @@ -512,11 +643,30 @@ static int ad4030_set_avg_frame_len(struct iio_dev *dev, int avg_val) > > struct ad4030_state *st = iio_priv(dev); > > unsigned int avg_log2 = ilog2(avg_val); > > unsigned int last_avg_idx = ARRAY_SIZE(ad4030_average_modes) - 1; > > + int freq_hz; > > int ret; > > > > if (avg_val < 0 || avg_val > ad4030_average_modes[last_avg_idx]) > > return -EINVAL; > > > > + if (st->offload_trigger) { > > + /* > > + * The sample averaging and sampling frequency configurations > > + * are mutually dependent one from another. That's because the > > s/one from another/on each other/ > > "one from another" makes it sound like they are independent rather than > dependent. Ack. > > > + * effective data sample rate is fCNV / 2^N, where N is the > > + * number of samples being averaged. > > + * > > + * When SPI offload is supported and we have control over the > > + * sample rate, the conversion start signal (CNV) and the SPI > > + * offload trigger frequencies must be re-evaluated so data is > > + * fetched only after 'avg_val' conversions. > > + */ > > + ad4030_get_sampling_freq(st, &freq_hz); > > + ret = ad4030_update_conversion_rate(st, freq_hz, avg_log2); > > + if (ret) > > + return ret; > > + } > > + > LGTM. > > Reviewed-by: David Lechner > Thanks, Marcelo