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Message-Id: <CDIOK6DFUNE0.2P8L2AL8MDAK1@shaak>
Date: Fri, 13 Aug 2021 16:51:12 -0400
From: "Liam Beguin" <liambeguin@...il.com>
To: "Jonathan Cameron" <jic23@...nel.org>
Cc: <lars@...afoo.de>, <Michael.Hennerich@...log.com>,
<charles-antoine.couret@...ensium.com>, <Nuno.Sa@...log.com>,
<linux-kernel@...r.kernel.org>, <linux-iio@...r.kernel.org>,
<devicetree@...r.kernel.org>, <robh+dt@...nel.org>
Subject: Re: [PATCH v5 3/5] iio: adc: ad7949: add support for internal vref
On Mon Aug 9, 2021 at 3:42 PM EDT, Jonathan Cameron wrote:
> ...
> > +
> > > > static int ad7949_spi_probe(struct spi_device *spi)
> > > > {
> > > > u32 spi_ctrl_mask = spi->controller->bits_per_word_mask;
> > > > struct device *dev = &spi->dev;
> > > > const struct ad7949_adc_spec *spec;
> > > > struct ad7949_adc_chip *ad7949_adc;
> > > > + struct ad7949_channel *ad7949_chan;
> > > > + struct fwnode_handle *child;
> > > > struct iio_dev *indio_dev;
> > > > + int mode;
> > > > + u32 tmp;
> > > > int ret;
> > > > + int i;
> > > >
> > > > indio_dev = devm_iio_device_alloc(dev, sizeof(*ad7949_adc));
> > > > if (!indio_dev) {
> > > > @@ -343,16 +383,82 @@ static int ad7949_spi_probe(struct spi_device *spi)
> > > > return -EINVAL;
> > > > }
> > > >
> > > > - ad7949_adc->vref = devm_regulator_get(dev, "vref");
> > > > + /* Setup external voltage ref, buffered? */
> > > > + ad7949_adc->vref = devm_regulator_get_optional(dev, "vrefin");
> > > > if (IS_ERR(ad7949_adc->vref)) {
> > > > - dev_err(dev, "fail to request regulator\n");
> > > > - return PTR_ERR(ad7949_adc->vref);
> > > > + ret = PTR_ERR(ad7949_adc->vref);
> > > > + if (ret != -ENODEV)
> > > > + return ret;
> > > > + /* unbuffered? */
> > > > + ad7949_adc->vref = devm_regulator_get_optional(dev, "vref");
> > > > + if (IS_ERR(ad7949_adc->vref)) {
> > > > + ret = PTR_ERR(ad7949_adc->vref);
> > > > + if (ret != -ENODEV)
> > > > + return ret;
> > > > + /* Internal then */
> > > > + mode = AD7949_CFG_VAL_REF_INT_4096;
> > > > + } else {
> > > > + mode = AD7949_CFG_VAL_REF_EXT_TEMP;
> > > > + }
> > > > + } else {
> > > > + mode = AD7949_CFG_VAL_REF_EXT_TEMP_BUF;
> > > > }
> > > >
> > > > - ret = regulator_enable(ad7949_adc->vref);
> > > > - if (ret < 0) {
> > > > - dev_err(dev, "fail to enable regulator\n");
> > > > - return ret;
> > > > + if (mode & AD7949_CFG_VAL_REF_EXTERNAL) {
> > > > + ret = regulator_enable(ad7949_adc->vref);
> > > > + if (ret < 0) {
> > > > + dev_err(dev, "fail to enable regulator\n");
> > > > + return ret;
> > > > + }
> > > > +
> > > > + ret = devm_add_action_or_reset(dev, ad7949_disable_reg,
> > > > + ad7949_adc->vref);
> > > > + if (ret)
> > > > + return ret;
> > > > + }
> > > > +
> > > > + ad7949_adc->channels = devm_kcalloc(dev, spec->num_channels,
> > > > + sizeof(*ad7949_adc->channels),
> > > > + GFP_KERNEL);
> > > > + if (!ad7949_adc->channels) {
> > > > + dev_err(dev, "unable to allocate ADC channels\n");
> > > > + return -ENOMEM;
> > > > + }
> > > > +
> > > > + /* Initialize all channel structures */
> > > > + for (i = 0; i < spec->num_channels; i++)
> > > > + ad7949_adc->channels[i].refsel = mode;
> > > > +
> > > > + /* Read channel specific information form the devicetree */
> > > > + device_for_each_child_node(dev, child) {
> > > > + ret = fwnode_property_read_u32(child, "reg", &i);
> > > > + if (ret) {
> > > > + dev_err(dev, "missing reg property in %pfw\n", child);
> > > > + fwnode_handle_put(child);
> > > > + return ret;
> > > > + }
> > > > +
> > > > + ad7949_chan = &ad7949_adc->channels[i];
> > > > +
> > > > + ret = fwnode_property_read_u32(child, "adi,internal-ref-microvolt", &tmp);
> > > > + if (ret < 0 && ret != -EINVAL) {
> > > > + dev_err(dev, "invalid internal reference in %pfw\n", child);
> > > > + fwnode_handle_put(child);
> > > > + return ret;
> > > > + }
> >
> > Hi Jonathan,
> >
> > >
> > > So if we are using external voltage, then we'd not expect this to exist.
> > > ret != -EINVAL should deal with that. However, we then hit the following
> > > switch
> > > and temp isn't set to an appropriate value so we get the error.
> > >
> > > Am I missing something?
> >
> > You're right that using an external reference, will cause this to fail.
> > My apologies, I've done a poor job of testing the last two revisions of
> > this patch. I'll do better.
> >
> > Since a regulator is also required when we're using an external source,
> > I'll add a check for that. Something like this:
> >
> > ret = fwnode_property_read_u32(child, "adi,internal-ref-microvolt", &tmp);
> > if (ret == -EINVAL && mode & AD7949_CFG_VAL_REF_EXTERNAL) {
> > continue;
> > } else if (ret < 0) {
> > dev_err(dev, "invalid voltage reference in %pfw\n", child);
> > fwnode_handle_put(child);
> > return ret;
> > }
>
> Makes sense.
Hi Jonathan,
After getting access to another setup to run more tests, I noticed
that setting the reference per channel isn't really feasible.
It take a little while for the reference to be updated internally even
though the request is sent out properly, and reading channels in a
sequence returns bad values.
I'll resend this without the per-channel configuration and make
adi,internal-ref-microvolt a global parameter.
Sorry about that,
Liam
>
> >
> > Given that we can now have a different scale for each channel based on
> > the vref source, should BIT(IIO_CHAN_INFO_SCALE) be moved to
> > .info_mask_separate in the channel definition?
> Yes, good point.
>
> Hopefully no one will notice the ABI change *crosses fingers*.
>
> Jonathan
>
> >
> > Thanks,
> > Liam
> >
> > >
> > > > +
> > > > + switch (tmp) {
> > > > + case 2500000:
> > > > + ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_2500;
> > > > + break;
> > > > + case 4096000:
> > > > + ad7949_chan->refsel = AD7949_CFG_VAL_REF_INT_4096;
> > > > + break;
> > > > + default:
> > > > + dev_err(dev, "unsupported internal voltage reference\n");
> > > > + fwnode_handle_put(child);
> > > > + return -EINVAL;
> > > > + }
> > > > }
> > > >
> > > > mutex_init(&ad7949_adc->lock);
> > > > @@ -373,7 +479,6 @@ static int ad7949_spi_probe(struct spi_device *spi)
> > > >
> > > > err:
> > > > mutex_destroy(&ad7949_adc->lock);
> > > > - regulator_disable(ad7949_adc->vref);
> > > >
> > > > return ret;
> > > > }
> > > > @@ -385,7 +490,6 @@ static int ad7949_spi_remove(struct spi_device *spi)
> > > >
> > > > iio_device_unregister(indio_dev);
> > > > mutex_destroy(&ad7949_adc->lock);
> > > > - regulator_disable(ad7949_adc->vref);
> > > >
> > > > return 0;
> > > > }
> >
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