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Message-ID: <8a8432e7-86b9-43dd-9aa0-75875747eedb@baylibre.com>
Date: Mon, 10 Feb 2025 10:01:57 -0600
From: David Lechner <dlechner@...libre.com>
To: Mark Brown <broonie@...nel.org>, Jonathan Cameron <jic23@...nel.org>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>, Nuno Sá
<nuno.sa@...log.com>
Cc: Uwe Kleine-König <ukleinek@...nel.org>,
Michael Hennerich <Michael.Hennerich@...log.com>,
Lars-Peter Clausen <lars@...afoo.de>, David Jander <david@...tonic.nl>,
Martin Sperl <kernel@...tin.sperl.org>, linux-spi@...r.kernel.org,
devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-iio@...r.kernel.org, Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v8 14/17] iio: adc: ad4695: Add support for SPI offload
On 2/7/25 2:09 PM, David Lechner wrote:
> Add support for SPI offload to the ad4695 driver. SPI offload allows
> sampling data at the max sample rate (500kSPS or 1MSPS).
>
> This is developed and tested against the ADI example FPGA design for
> this family of ADCs [1].
>
> [1]: http://analogdevicesinc.github.io/hdl/projects/ad469x_fmc/index.html
>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Reviewed-by: Nuno Sa <nuno.sa@...log.com>
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---
>
...
> ---
> drivers/iio/adc/Kconfig | 1 +
> drivers/iio/adc/ad4695.c | 445 +++++++++++++++++++++++++++++++++++++++++++++--
> 2 files changed, 429 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/iio/adc/Kconfig b/drivers/iio/adc/Kconfig
> index 995b9cacbaa964d26424346120c139858f93cdcd..ec60b64c46e187e2be18ab1f8ca9e6f4f03299f9 100644
> --- a/drivers/iio/adc/Kconfig
> +++ b/drivers/iio/adc/Kconfig
> @@ -52,6 +52,7 @@ config AD4695
> tristate "Analog Device AD4695 ADC Driver"
> depends on SPI
> select IIO_BUFFER
> + select IIO_BUFFER_DMAENGINE
> select IIO_TRIGGERED_BUFFER
> select REGMAP
I missed adding
select SPI_OFFLOAD
Closes: https://lore.kernel.org/oe-kbuild-all/202502090910.ganYXEeF-lkp@intel.com/
> help
...
> +static int ad4695_offload_buffer_postenable(struct iio_dev *indio_dev)
> +{
> + struct ad4695_state *st = iio_priv(indio_dev);
> + struct spi_offload_trigger_config config = {
> + .type = SPI_OFFLOAD_TRIGGER_DATA_READY,
> + };
> + struct spi_transfer *xfer = &st->buf_read_xfer[0];
> + struct pwm_state state;
> + u8 temp_chan_bit = st->chip_info->num_voltage_inputs;
> + u8 num_slots = 0;
> + u8 temp_en = 0;
> + unsigned int bit;
> + int ret;
> +
> + iio_for_each_active_channel(indio_dev, bit) {
> + if (bit == temp_chan_bit) {
> + temp_en = 1;
> + continue;
> + }
> +
> + ret = regmap_write(st->regmap, AD4695_REG_AS_SLOT(num_slots),
> + FIELD_PREP(AD4695_REG_AS_SLOT_INX, bit));
> + if (ret)
> + return ret;
> +
> + num_slots++;
> + }
> +
> + /*
> + * For non-offload, we could discard data to work around this
> + * restriction, but with offload, that is not possible.
> + */
> + if (num_slots < 2) {
> + dev_err(&st->spi->dev,
> + "At least two voltage channels must be enabled.\n");
> + return -EINVAL;
> + }
> +
> + ret = regmap_update_bits(st->regmap, AD4695_REG_TEMP_CTRL,
> + AD4695_REG_TEMP_CTRL_TEMP_EN,
> + FIELD_PREP(AD4695_REG_TEMP_CTRL_TEMP_EN,
> + temp_en));
> + if (ret)
> + return ret;
> +
> + /* Each BUSY event means just one sample for one channel is ready. */
> + memset(xfer, 0, sizeof(*xfer));
> + xfer->offload_flags = SPI_OFFLOAD_XFER_RX_STREAM;
> + /* Using 19 bits per word to allow for possible oversampling */
> + xfer->bits_per_word = 19;
> + xfer->len = 4;
> +
> + spi_message_init_with_transfers(&st->buf_read_msg, xfer, 1);
> + st->buf_read_msg.offload = st->offload;
> +
> + ret = spi_optimize_message(st->spi, &st->buf_read_msg);
> + if (ret)
> + return ret;
> +
> + /*
> + * NB: technically, this is part the SPI offload trigger enable, but it
> + * doesn't work to call it from the offload trigger enable callback
> + * because it requires accessing the SPI bus. Calling it from the
> + * trigger enable callback could cause a deadlock.
> + */
> + ret = regmap_set_bits(st->regmap, AD4695_REG_GP_MODE,
> + AD4695_REG_GP_MODE_BUSY_GP_EN);
> + if (ret)
> + goto err_unoptimize_message;
> +
> + ret = spi_offload_trigger_enable(st->offload, st->offload_trigger,
> + &config);
> + if (ret)
> + goto err_disable_busy_output;
> +
> + ret = ad4695_enter_advanced_sequencer_mode(st, num_slots);
> + if (ret)
> + goto err_offload_trigger_disable;
> +
> + guard(mutex)(&st->cnv_pwm_lock);
Apparently clang doesn't like this guard() after goto, so I'll have to figure
out what to do about that. Probably need to add a helper function to avoid
goto below from jumping out of scoped_guard().
https://lore.kernel.org/oe-kbuild-all/202502090806.KxEvxCZC-lkp@intel.com/
> + pwm_get_state(st->cnv_pwm, &state);
> + /*
> + * PWM subsystem generally rounds down, so requesting 2x minimum high
> + * time ensures that we meet the minimum high time in any case.
> + */
> + state.duty_cycle = AD4695_T_CNVH_NS * 2;
> + ret = pwm_apply_might_sleep(st->cnv_pwm, &state);
> + if (ret)
> + goto err_offload_exit_conversion_mode;
> +
> + return 0;
> +
> +err_offload_exit_conversion_mode:
> + /*
> + * We have to unwind in a different order to avoid triggering offload.
> + * ad4695_exit_conversion_mode() triggers a conversion, so it has to be
> + * done after spi_offload_trigger_disable().
> + */
> + spi_offload_trigger_disable(st->offload, st->offload_trigger);
> + ad4695_exit_conversion_mode(st);
> + goto err_disable_busy_output;
> +
> +err_offload_trigger_disable:
> + spi_offload_trigger_disable(st->offload, st->offload_trigger);
> +
> +err_disable_busy_output:
> + regmap_clear_bits(st->regmap, AD4695_REG_GP_MODE,
> + AD4695_REG_GP_MODE_BUSY_GP_EN);
> +
> +err_unoptimize_message:
> + spi_unoptimize_message(&st->buf_read_msg);
> +
> + return ret;
> +}
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