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References: <20210804140309.31468-1-puranjay12@gmail.com> <20210804140309.31468-4-puranjay12@gmail.com>
 <20210808162936.7066403b@jic23-huawei> <20210808163625.33e1153b@jic23-huawei>
In-Reply-To: <20210808163625.33e1153b@jic23-huawei>
From:   Puranjay Mohan <puranjay12@gmail.com>
Date:   Fri, 13 Aug 2021 13:51:44 +0530
Message-ID: <CANk7y0iUbjseC1qQw=94BhZw3=55VLRuhczt0+3t_2jMZOX88w@mail.gmail.com>
Subject: Re: [PATCH v8 3/3] iio: accel: adxl355: Add triggered buffer support
To:     Jonathan Cameron <jic23@kernel.org>
Cc:     "Hennerich, Michael" <Michael.Hennerich@analog.com>,
        devicetree <devicetree@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        "Bogdan, Dragos" <Dragos.Bogdan@analog.com>,
        "Berghe, Darius" <Darius.Berghe@analog.com>
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Precedence: bulk

On Sun, Aug 8, 2021 at 9:03 PM Jonathan Cameron <jic23@kernel.org> wrote:
>
> On Sun, 8 Aug 2021 16:29:36 +0100
> Jonathan Cameron <jic23@kernel.org> wrote:
>
> > On Wed,  4 Aug 2021 19:33:09 +0530
> > Puranjay Mohan <puranjay12@gmail.com> wrote:
> >
> > > Provide a way for continuous data capture by setting up buffer support. The
> > > data ready signal exposed at the DRDY pin of the ADXL355 is exploited as
> > > a hardware interrupt which triggers to fill the buffer.
> > >
> > > Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
> >
> > Hi Puranjay,
> >
> > This device has a hardware fifo, so we need to be careful how we add
> > trigger support such that we can enable that smoothly.
> Oops. I meant to come back and add some detail on this after taking a look
> at the datasheet.
>
> The device has an explicit data ready pin to indicate 'any data' not using
> the fifo.  That's helpful for this mode.  I note that there is a way of
> turning it off which is good and you should ensure it is off, except when
> the trigger is enabled so that we aren't dealing with a stream of spurious
> interrupts.

I have added a function in trigger_ops to enable this, and I have
turned this off in the setup.
>
> I would encourage you to also get the fifo mode up and running before sending
> a new version of this patch.  It may well be the case that there is little
> point in supporting this mode as it's just a special case of fifo mode with
> the watermark set to 1.
I am short on time now, will have to do the fifo later.
>
> >
> > There are a few things in here that suggest this isn't tested as much
> > as I'd expect for a submission.  If you are posting early, but need
> > to do more testing, please state that clearly.
> >
> > Jonathan
> >
> > > ---
> > >  drivers/iio/accel/Kconfig        |   4 ++
> > >  drivers/iio/accel/adxl355.h      |   2 +-
> > >  drivers/iio/accel/adxl355_core.c | 102 ++++++++++++++++++++++++++++++-
> > >  drivers/iio/accel/adxl355_i2c.c  |   3 +-
> > >  drivers/iio/accel/adxl355_spi.c  |   2 +-
> > >  5 files changed, 108 insertions(+), 5 deletions(-)
> > >
> > > diff --git a/drivers/iio/accel/Kconfig b/drivers/iio/accel/Kconfig
> > > index d0c45c809..9c16c1841 100644
> > > --- a/drivers/iio/accel/Kconfig
> > > +++ b/drivers/iio/accel/Kconfig
> > > @@ -69,6 +69,8 @@ config ADXL355_I2C
> > >     depends on I2C
> > >     select ADXL355
> > >     select REGMAP_I2C
> > > +   select IIO_BUFFER
> > > +   select IIO_TRIGGERED_BUFFER
> > >     help
> > >       Say Y here if you want to build i2c support for the Analog Devices
> > >       ADXL355 3-axis digital accelerometer.
> > > @@ -82,6 +84,8 @@ config ADXL355_SPI
> > >     depends on SPI
> > >     select ADXL355
> > >     select REGMAP_SPI
> > > +   select IIO_BUFFER
> > > +   select IIO_TRIGGERED_BUFFER
> > >     help
> > >       Say Y here if you want to build spi support for the Analog Devices
> > >       ADXL355 3-axis digital accelerometer.
> > > diff --git a/drivers/iio/accel/adxl355.h b/drivers/iio/accel/adxl355.h
> > > index 322b0abb8..f0a376e6d 100644
> > > --- a/drivers/iio/accel/adxl355.h
> > > +++ b/drivers/iio/accel/adxl355.h
> > > @@ -15,5 +15,5 @@ extern const struct regmap_access_table adxl355_readable_regs_tbl;
> > >  extern const struct regmap_access_table adxl355_writeable_regs_tbl;
> > >
> > >  int adxl355_core_probe(struct device *dev, struct regmap *regmap,
> > > -                  const char *name);
> > > +                  const char *name, int irq);
> > >  #endif /* _ADXL355_H_ */
> > > diff --git a/drivers/iio/accel/adxl355_core.c b/drivers/iio/accel/adxl355_core.c
> > > index 47fbb31bc..f9dc2a530 100644
> > > --- a/drivers/iio/accel/adxl355_core.c
> > > +++ b/drivers/iio/accel/adxl355_core.c
> > > @@ -9,6 +9,10 @@
> > >
> > >  #include <asm/unaligned.h>
> > >  #include <linux/bitfield.h>
> > > +#include <linux/iio/buffer.h>
> > > +#include <linux/iio/trigger.h>
> > > +#include <linux/iio/triggered_buffer.h>
> > > +#include <linux/iio/trigger_consumer.h>
> > >  #include <linux/iio/iio.h>
> > >  #include <linux/limits.h>
> > >  #include <linux/math64.h>
> > > @@ -172,6 +176,7 @@ static const struct adxl355_chan_info adxl355_chans[] = {
> > >  };
> > >
> > >  struct adxl355_data {
> > > +   int irq;
> > >     struct regmap *regmap;
> > >     struct device *dev;
> > >     struct mutex lock; /* lock to protect op_mode */
> > > @@ -181,6 +186,12 @@ struct adxl355_data {
> > >     int calibbias[3];
> > >     int adxl355_hpf_3db_table[7][2];
> > >     u8 transf_buf[3] ____cacheline_aligned;
> > > +   struct iio_trigger      *dready_trig;
> > > +   /* Ensure correct alignment of timestamp when present */
> > > +   struct {
> > > +           __be32 channels[3];
> > > +           s64 ts;
> > > +   } buffer ____cacheline_aligned;
> >
> > Interesting quirk here is that we need to ensure that any of the
> > buffers used for DMA don't share a cacheline with other data, but we don't
> > need to ensure they don't share with each other.  As such, this can
> > share fine with transf_buf, but definitely not with dready_trig (which
> > can't share with transf_buf like it is right now).
> >
> > So reorder to put the various DMA safe buffers at the end, and ensure
> > the first one is cacheline aligned.
> >
> > Even better, given you can only safely access one at a time anyway
> > (and I think you always hold the lock so that is fine), put them in a union
> > to make it explicit that only one is used at a time.
> >
> > struct iio_trigger *dready_trig;
> > union {
> >       u8 trans_buf[3];
> >       struct {
> >               __be32 channels[3];
> >               s64 ts;
> >       } buffer;
> > } ___cacheline_algned;
> > or something like that.
Thanks for suggesting this snippet, it works perfectly.
> >
> >
> >
> > >  };
> > >
> > >  static int adxl355_set_op_mode(struct adxl355_data *data,
> > > @@ -499,12 +510,46 @@ static int adxl355_read_avail(struct iio_dev *indio_dev,
> > >     }
> > >  }
> > >
> > > +static const unsigned long adxl355_avail_scan_masks[] = {
> > > +   GENMASK(3, 0),
> > > +   0
> > > +};
> > > +
> > >  static const struct iio_info adxl355_info = {
> > >     .read_raw       = adxl355_read_raw,
> > >     .write_raw      = adxl355_write_raw,
> > >     .read_avail     = &adxl355_read_avail
> > >  };
> > >
> > > +static const struct iio_trigger_ops adxl355_trigger_ops = {
> > > +   .validate_device = &iio_trigger_validate_own_device,
> >
> > No means of turning it on?
added a set state function.
> >
> > > +};
> > > +
> > > +static irqreturn_t adxl355_trigger_handler(int irq, void *p)
> > > +{
> > > +   struct iio_poll_func *pf = p;
> > > +   struct iio_dev *indio_dev = pf->indio_dev;
> > > +   struct adxl355_data *data = iio_priv(indio_dev);
> > > +   int ret;
> > > +
> > > +   mutex_lock(&data->lock);
> > > +
> > > +   ret = regmap_bulk_read(data->regmap, ADXL355_XDATA3_REG,
> > > +                          data->buffer.channels,
> > > +                          9);
> >
> > That doesn't look right.  you are reading 9 bytes into an array of 3 __be32 channels.
> > You should check the data is turning up where it should.
I have fixed this in the next version,
> >
> >
> > > +   if (ret)
> > > +           goto out_unlock_notify;
> > > +
> > > +   iio_push_to_buffers_with_timestamp(indio_dev, &data->buffer,
> > > +                                      pf->timestamp);
> > > +
> > > +out_unlock_notify:
> > > +   mutex_unlock(&data->lock);
> > > +   iio_trigger_notify_done(indio_dev->trig);
> > > +
> > > +   return IRQ_HANDLED;
> > > +}
> > > +
> > >  #define ADXL355_ACCEL_CHANNEL(index, reg, axis) {                  \
> > >     .type = IIO_ACCEL,                                              \
> > >     .address = reg,                                                 \
> > > @@ -518,6 +563,7 @@ static const struct iio_info adxl355_info = {
> > >     .info_mask_shared_by_type_available =                           \
> > >             BIT(IIO_CHAN_INFO_SAMP_FREQ) |                          \
> > >             BIT(IIO_CHAN_INFO_HIGH_PASS_FILTER_3DB_FREQUENCY),      \
> > > +   .scan_index = index,                                            \
> > >     .scan_type = {                                                  \
> > >             .sign = 's',                                            \
> > >             .realbits = 20,                                         \
> > > @@ -537,17 +583,56 @@ static const struct iio_chan_spec adxl355_channels[] = {
> > >             .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
> > >                                   BIT(IIO_CHAN_INFO_SCALE) |
> > >                                   BIT(IIO_CHAN_INFO_OFFSET),
> > > +           .scan_index = 3,
> > >             .scan_type = {
> > >                     .sign = 's',
> > >                     .realbits = 12,
> > >                     .storagebits = 16,
> > >                     .endianness = IIO_BE,
> > >             },
> > > -   }
> > > +   },
> >
> > If you do end up respinning patch 2, add the comma in that patch as it'll reduced
> > noise here.
> >
> > > +   IIO_CHAN_SOFT_TIMESTAMP(4)
> > >  };
> > >
> > > +static int adxl355_probe_trigger(struct iio_dev *indio_dev)
> > > +{
> > > +   struct adxl355_data *data = iio_priv(indio_dev);
> > > +   int ret;
> > > +
> > > +   if (!data->irq) {
> > > +           dev_info(data->dev, "no irq, using polling\n");
> > > +           return 0;
> > > +   }
> > > +
> > > +   data->dready_trig = devm_iio_trigger_alloc(data->dev, "%s-dev%d",
> > > +                                              indio_dev->name,
> > > +                                              indio_dev->id);
> > > +   if (!data->dready_trig)
> > > +           return -ENOMEM;
> > > +
> > > +   data->dready_trig->ops = &adxl355_trigger_ops;
> > > +   iio_trigger_set_drvdata(data->dready_trig, indio_dev);
> > > +
> > > +   ret = devm_request_irq(data->dev, data->irq,
> > > +                          &iio_trigger_generic_data_rdy_poll,
> > > +                          IRQF_ONESHOT, "adxl355_irq", data->dready_trig);
> > > +   if (ret < 0)
> > > +           return dev_err_probe(data->dev, ret, "request irq %d failed\n",
> > > +                                data->irq);
> > > +
> > > +   ret = devm_iio_trigger_register(data->dev, data->dready_trig);
> > > +   if (ret) {
> > > +           dev_err(data->dev, "iio trigger register failed\n");
> > > +           return ret;
> > > +   }
> > > +
> > > +   indio_dev->trig = iio_trigger_get(data->dready_trig);
> > > +
> > > +   return 0;
> > > +}
> > > +
> > >  int adxl355_core_probe(struct device *dev, struct regmap *regmap,
> > > -                  const char *name)
> > > +                  const char *name, int irq)
> > >  {
> > >     struct adxl355_data *data;
> > >     struct iio_dev *indio_dev;
> > > @@ -560,6 +645,7 @@ int adxl355_core_probe(struct device *dev, struct regmap *regmap,
> > >     data = iio_priv(indio_dev);
> > >     data->regmap = regmap;
> > >     data->dev = dev;
> > > +   data->irq = irq;
> > >     data->op_mode = ADXL355_STANDBY;
> > >     mutex_init(&data->lock);
> > >
> > > @@ -568,6 +654,7 @@ int adxl355_core_probe(struct device *dev, struct regmap *regmap,
> > >     indio_dev->modes = INDIO_DIRECT_MODE;
> > >     indio_dev->channels = adxl355_channels;
> > >     indio_dev->num_channels = ARRAY_SIZE(adxl355_channels);
> > > +   indio_dev->available_scan_masks = adxl355_avail_scan_masks;
> > >
> > >     ret = adxl355_setup(data);
> > >     if (ret < 0) {
> > > @@ -575,6 +662,17 @@ int adxl355_core_probe(struct device *dev, struct regmap *regmap,
> > >             return ret;
> > >     }
> > >
> > > +   ret = devm_iio_triggered_buffer_setup(dev, indio_dev,
> > > +                                         &iio_pollfunc_store_time,
> > > +                                         &adxl355_trigger_handler, NULL);
> > > +   if (ret < 0)
> >
> > if (ret) preferred, because it is more consistent with returning devm_iio_device_register()
> > below (where we are assuming negative or 0 only)
> >
> > > +           return dev_err_probe(dev, ret,
> > > +                                "iio triggered buffer setup failed\n");
> > > +
> > > +   ret = adxl355_probe_trigger(indio_dev);
> > > +   if (ret < 0)
> > > +           return ret;
> > > +
> > >     return devm_iio_device_register(dev, indio_dev);
> > >  }
> > >  EXPORT_SYMBOL_GPL(adxl355_core_probe);
> > > diff --git a/drivers/iio/accel/adxl355_i2c.c b/drivers/iio/accel/adxl355_i2c.c
> > > index e3070ee81..c18521819 100644
> > > --- a/drivers/iio/accel/adxl355_i2c.c
> > > +++ b/drivers/iio/accel/adxl355_i2c.c
> > > @@ -31,7 +31,8 @@ static int adxl355_i2c_probe(struct i2c_client *client)
> > >             return PTR_ERR(regmap);
> > >     }
> > >
> > > -   return adxl355_core_probe(&client->dev, regmap, client->name);
> > > +   return adxl355_core_probe(&client->dev, regmap, client->name,
> > > +                             client->irq);
> >
> > We can't just use the first interrupt (which this corresponds to) because
> > the device supports 3 and who knows if this is the right one?
> >
> > Now to solve this, we run into a 'fun' issue.  We want to use the generic
> > firmware property interfaces (include/linux/property.h) but that doesn't
> > include a fwnode_irq_get_by_name()
> >
> > We've had some recent discussion about this:
> > https://lore.kernel.org/linux-iio/20210724190614.3593dcd1@jic23-huawei/
> >
> > If it is something you would like to take on, that would be great.
> > If not, for now use the of_irq_get_byname() method but add a comment
> > saying it would good to move to a generic version.
I really want to work on fwnode_irq_get_by_name() but I am short on
time, I will work on it next month.
this would be a nice project for me, btw.
> >
> > >  }
> > >
> > >  static const struct i2c_device_id adxl355_i2c_id[] = {
> > > diff --git a/drivers/iio/accel/adxl355_spi.c b/drivers/iio/accel/adxl355_spi.c
> > > index a16bd1407..f9ba153f6 100644
> > > --- a/drivers/iio/accel/adxl355_spi.c
> > > +++ b/drivers/iio/accel/adxl355_spi.c
> > > @@ -34,7 +34,7 @@ static int adxl355_spi_probe(struct spi_device *spi)
> > >             return PTR_ERR(regmap);
> > >     }
> > >
> > > -   return adxl355_core_probe(&spi->dev, regmap, id->name);
> > > +   return adxl355_core_probe(&spi->dev, regmap, id->name, spi->irq);
> > >  }
> > >
> > >  static const struct spi_device_id adxl355_spi_id[] = {
> >
>


-- 
Thanks and Regards

Yours Truly,

Puranjay Mohan