Re: [PATCH v4 5/9] iio: adc: mcp3911: add support for buffers

[Marcus Folkesson <marcus.folkesson@gmail.com>]

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Hi Jonathan,

On Sun, Jul 31, 2022 at 05:51:21PM +0100, Jonathan Cameron wrote:
> On Fri, 22 Jul 2022 15:07:22 +0200
> Marcus Folkesson <marcus.folkesson@gmail.com> wrote:
> 
> > Add support for buffers to make the driver fit for more usecases.
> > 
> > Signed-off-by: Marcus Folkesson <marcus.folkesson@gmail.com>
> > Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
> 
> Assuming the Kconfig change from previous patch is pulled into this one...

Yep

> 
> A few questions / comments inline.
> 
> Thanks,
> 
> Jonathan
> 
> > ---
> >  drivers/iio/adc/mcp3911.c | 96 ++++++++++++++++++++++++++++++++++++---
> >  1 file changed, 89 insertions(+), 7 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/mcp3911.c b/drivers/iio/adc/mcp3911.c
> > index 00dadb1761dc..96c0a2a50c7c 100644
> > --- a/drivers/iio/adc/mcp3911.c
> > +++ b/drivers/iio/adc/mcp3911.c
> > @@ -5,15 +5,22 @@
> >   * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@gmail.com>
> >   * Copyright (C) 2018 Kent Gustavsson <kent@minoris.se>
> >   */
> > +#include <linux/bitfield.h>
> > +#include <linux/bits.h>
> >  #include <linux/clk.h>
> >  #include <linux/delay.h>
> >  #include <linux/err.h>
> >  #include <linux/iio/iio.h>
> > +#include <linux/iio/buffer.h>
> > +#include <linux/iio/triggered_buffer.h>
> > +#include <linux/iio/trigger_consumer.h>
> > +#include <linux/iio/trigger.h>
> >  #include <linux/module.h>
> >  #include <linux/mod_devicetable.h>
> >  #include <linux/property.h>
> >  #include <linux/regulator/consumer.h>
> >  #include <linux/spi/spi.h>
> 
> Line break here to separate the 'chunks' of includes.
> 

OK

> > +#include <asm/unaligned.h>
> >  
> >  #define MCP3911_REG_CHANNEL0		0x00
> >  #define MCP3911_REG_CHANNEL1		0x03
> > @@ -22,6 +29,7 @@
> >  #define MCP3911_REG_GAIN		0x09
> >  
> >  #define MCP3911_REG_STATUSCOM		0x0a
> > +#define MCP3911_STATUSCOM_READ		GENMASK(7, 6)
> >  #define MCP3911_STATUSCOM_CH1_24WIDTH	BIT(4)
> >  #define MCP3911_STATUSCOM_CH0_24WIDTH	BIT(3)
> >  #define MCP3911_STATUSCOM_EN_OFFCAL	BIT(2)
> > @@ -54,6 +62,13 @@ struct mcp3911 {
> >  	struct regulator *vref;
> >  	struct clk *clki;
> >  	u32 dev_addr;
> > +	struct {
> > +		u32 channels[MCP3911_NUM_CHANNELS];
> > +		s64 ts __aligned(8);
> > +	} scan;
> > +
> > +	u8 tx_buf[MCP3911_NUM_CHANNELS * 3] __aligned(IIO_DMA_MINALIGN);
> > +	u8 rx_buf[MCP3911_NUM_CHANNELS * 3];
> >  };
> >  
> >  static int mcp3911_read(struct mcp3911 *adc, u8 reg, u32 *val, u8 len)
> > @@ -196,16 +211,63 @@ static int mcp3911_write_raw(struct iio_dev *indio_dev,
> >  		.type = IIO_VOLTAGE,				\
> >  		.indexed = 1,					\
> >  		.channel = idx,					\
> > +		.scan_index = idx,				\
> >  		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |	\
> >  			BIT(IIO_CHAN_INFO_OFFSET) |		\
> >  			BIT(IIO_CHAN_INFO_SCALE),		\
> > +		.scan_type = {					\
> > +			.sign = 's',				\
> > +			.realbits = 24,				\
> > +			.storagebits = 32,			\
> > +			.endianness = IIO_BE,			\
> > +		},						\
> >  }
> >  
> >  static const struct iio_chan_spec mcp3911_channels[] = {
> >  	MCP3911_CHAN(0),
> >  	MCP3911_CHAN(1),
> > +	IIO_CHAN_SOFT_TIMESTAMP(2),
> >  };
> >  
> > +static irqreturn_t mcp3911_trigger_handler(int irq, void *p)
> > +{
> > +	struct iio_poll_func *pf = p;
> > +	struct iio_dev *indio_dev = pf->indio_dev;
> > +	struct mcp3911 *adc = iio_priv(indio_dev);
> > +	struct spi_transfer xfer = {
> > +		.tx_buf = adc->tx_buf,
> > +		.rx_buf = adc->rx_buf,
> > +		.len = sizeof(adc->rx_buf),
> > +	};
> > +	int scan_index;
> > +	int i = 0;
> > +	int ret;
> > +
> > +	mutex_lock(&adc->lock);
> > +	adc->tx_buf[0] = MCP3911_REG_READ(MCP3911_CHANNEL(0), adc->dev_addr);
> > +	ret = spi_sync_transfer(adc->spi, &xfer, 1);
> > +	if (ret < 0) {
> > +		dev_warn(&adc->spi->dev,
> > +				"failed to get conversion data\n");
> > +		goto out;
> > +	}
> > +
> > +	for_each_set_bit(scan_index, indio_dev->active_scan_mask,
> > +			indio_dev->masklength) {
> > +		const struct iio_chan_spec *scan_chan = &indio_dev->channels[scan_index];
> > +
> > +		adc->scan.channels[i] = get_unaligned_be24(&adc->rx_buf[scan_chan->channel * 3]);
> 
> This has me a little curious.  It seems to be potentially reading from byte 0 which in the spi
> transfer is at the same time as the tx that tells the device what the command is.  I'd expect
> it to be one byte later.  Easiest way to do that being to have two transfers (though you could
> just add to the offset). I might be misremembering how the spi_transfer stuff works though.
> Been a while since I hacked anything SPI based...
> 

Good catch.
I did not even notice that the resolution of my plot-script was wrong...


> > +		i++;
> > +	}
> > +	iio_push_to_buffers_with_timestamp(indio_dev, &adc->scan,
> > +			iio_get_time_ns(indio_dev));
> > +out:
> > +	mutex_unlock(&adc->lock);
> > +	iio_trigger_notify_done(indio_dev->trig);
> > +
> > +	return IRQ_HANDLED;
> > +}
> > +
> >  static const struct iio_info mcp3911_info = {
> >  	.read_raw = mcp3911_read_raw,
> >  	.write_raw = mcp3911_write_raw,
> > @@ -214,7 +276,7 @@ static const struct iio_info mcp3911_info = {
> >  static int mcp3911_config(struct mcp3911 *adc)
> >  {
> >  	struct device *dev = &adc->spi->dev;
> > -	u32 configreg;
> > +	u32 regval;
> >  	int ret;
> >  
> >  	ret = device_property_read_u32(dev, "microchip,device-addr", &adc->dev_addr);
> > @@ -233,29 +295,43 @@ static int mcp3911_config(struct mcp3911 *adc)
> >  	}
> >  	dev_dbg(&adc->spi->dev, "use device address %i\n", adc->dev_addr);
> >  
> > -	ret = mcp3911_read(adc, MCP3911_REG_CONFIG, &configreg, 2);
> > +	ret = mcp3911_read(adc, MCP3911_REG_CONFIG, &regval, 2);
> 
> If I was being fussy I'd ask you to pull the refactoring in here out as a precusor
> patch to simplify reviewing the new stuff a little.  However it's fairly minor
> so I'll let that go this time.

Ok, I got you wrong. Thanks.


Best regards
Marcus Folkesson


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