From: Fabrice Gasnier <fabrice.gasnier@st.com>
To: <jic23@kernel.org>
Cc: <linux-arm-kernel@lists.infradead.org>,
<linux-kernel@vger.kernel.org>, <mcoquelin.stm32@gmail.com>,
<alexandre.torgue@st.com>, <fabrice.gasnier@st.com>,
<linux-iio@vger.kernel.org>, <lars@metafoo.de>, <knaack.h@gmx.de>,
<pmeerw@pmeerw.net>, <linux-stm32@st-md-mailman.stormreply.com>,
<arnaud.pouliquen@st.com>, <olivier.moysan@st.com>
Subject: [PATCH] iio: adc: stm32-dfsdm: improve sampling frequency accuracy
Date: Mon, 25 Mar 2019 15:24:01 +0100 [thread overview]
Message-ID: <1553523841-16315-1-git-send-email-fabrice.gasnier@st.com> (raw)
The sample frequency is driven using the oversampling ratio depending
on the SPI bus frequency.
Currently, oversampling ratio is computed by an entire division:
- spi_freq / sample_freq. This may result in inaccurate value.
Using DIV_ROUND_CLOSEST improves resulting sample frequency, which is
useful for audio that requests fixed rates (such as: 8, 16 or 32 kHz).
BTW, introduce new routine to re-factor sample frequency setting, and
move frequency accuracy message from warning to debug level.
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
---
drivers/iio/adc/stm32-dfsdm-adc.c | 56 +++++++++++++++++++++------------------
1 file changed, 30 insertions(+), 26 deletions(-)
diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index 531ca7e..051561c 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
@@ -558,13 +558,38 @@ static ssize_t dfsdm_adc_audio_get_spiclk(struct iio_dev *indio_dev,
return snprintf(buf, PAGE_SIZE, "%d\n", adc->spi_freq);
}
+static int dfsdm_adc_set_samp_freq(struct iio_dev *indio_dev,
+ unsigned int sample_freq,
+ unsigned int spi_freq)
+{
+ struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
+ struct stm32_dfsdm_filter *fl = &adc->dfsdm->fl_list[adc->fl_id];
+ unsigned int oversamp;
+ int ret;
+
+ oversamp = DIV_ROUND_CLOSEST(spi_freq, sample_freq);
+ if (spi_freq % sample_freq)
+ dev_dbg(&indio_dev->dev,
+ "Rate not accurate. requested (%u), actual (%u)\n",
+ sample_freq, spi_freq / oversamp);
+
+ ret = stm32_dfsdm_set_osrs(fl, 0, oversamp);
+ if (ret < 0) {
+ dev_err(&indio_dev->dev, "No filter parameters that match!\n");
+ return ret;
+ }
+ adc->sample_freq = spi_freq / oversamp;
+ adc->oversamp = oversamp;
+
+ return 0;
+}
+
static ssize_t dfsdm_adc_audio_set_spiclk(struct iio_dev *indio_dev,
uintptr_t priv,
const struct iio_chan_spec *chan,
const char *buf, size_t len)
{
struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
- struct stm32_dfsdm_filter *fl = &adc->dfsdm->fl_list[adc->fl_id];
struct stm32_dfsdm_channel *ch = &adc->dfsdm->ch_list[chan->channel];
unsigned int sample_freq = adc->sample_freq;
unsigned int spi_freq;
@@ -583,17 +608,9 @@ static ssize_t dfsdm_adc_audio_set_spiclk(struct iio_dev *indio_dev,
return -EINVAL;
if (sample_freq) {
- if (spi_freq % sample_freq)
- dev_warn(&indio_dev->dev,
- "Sampling rate not accurate (%d)\n",
- spi_freq / (spi_freq / sample_freq));
-
- ret = stm32_dfsdm_set_osrs(fl, 0, (spi_freq / sample_freq));
- if (ret < 0) {
- dev_err(&indio_dev->dev,
- "No filter parameters that match!\n");
+ ret = dfsdm_adc_set_samp_freq(indio_dev, sample_freq, spi_freq);
+ if (ret < 0)
return ret;
- }
}
adc->spi_freq = spi_freq;
@@ -1068,22 +1085,9 @@ static int stm32_dfsdm_write_raw(struct iio_dev *indio_dev,
spi_freq = adc->spi_freq;
}
- if (spi_freq % val)
- dev_warn(&indio_dev->dev,
- "Sampling rate not accurate (%d)\n",
- spi_freq / (spi_freq / val));
-
- ret = stm32_dfsdm_set_osrs(fl, 0, (spi_freq / val));
- if (ret < 0) {
- dev_err(&indio_dev->dev,
- "Not able to find parameter that match!\n");
- iio_device_release_direct_mode(indio_dev);
- return ret;
- }
- adc->sample_freq = val;
+ ret = dfsdm_adc_set_samp_freq(indio_dev, val, spi_freq);
iio_device_release_direct_mode(indio_dev);
-
- return 0;
+ return ret;
}
return -EINVAL;
--
2.7.4
next reply other threads:[~2019-03-25 14:25 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-25 14:24 Fabrice Gasnier [this message]
2019-03-31 9:46 ` [PATCH] iio: adc: stm32-dfsdm: improve sampling frequency accuracy Jonathan Cameron
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