On Tue, 18 Jun 2024 13:45:00 +0000 Guillaume Stols <gstols@xxxxxxxxxxxx> wrote: > Frstdata pin is set high during the first sample's transmission and then > set low. This code chunk attempts to recover from an eventual glitch in > the clock by checking frstdata state after reading the first channel's > sample. Currently, in serial mode, this check happens AFTER the 16th > pulse, and if frstdata is not set it resets the device and returns EINVAL. > According to the datasheet, "The FRSTDATA output returns to a logic low > following the 16th SCLK falling edge.", thus after the 16th pulse, the > check will always be true, and the driver will not work as expected. Thus > it must be removed for serial mode. when you say will not work as expected, is this is normal circumstances, or when dealing with a clock glitch? i.e. should this have a fixes tag and got upstream asap or is it just cleaning up a corner case and can wait for now? One trivial comment inline. Jonathan > > Signed-off-by: Guillaume Stols <gstols@xxxxxxxxxxxx> > --- > Changes in v2: > - Remove frstdata check only for the serial interface as suggested by > Michael Hennerich. > - Link to v1: https://lore.kernel.org/r/20240417-cleanup-ad7606-v1-1-5c2a29662c0a@xxxxxxxxxxxx > --- > drivers/iio/adc/ad7606.c | 28 ++----------------------- > drivers/iio/adc/ad7606.h | 2 ++ > drivers/iio/adc/ad7606_par.c | 49 +++++++++++++++++++++++++++++++++++++++++--- > 3 files changed, 50 insertions(+), 29 deletions(-) > > diff --git a/drivers/iio/adc/ad7606.c b/drivers/iio/adc/ad7606.c > index 3a417595294f..c321c6ef48df 100644 > --- a/drivers/iio/adc/ad7606.c > +++ b/drivers/iio/adc/ad7606.c > @@ -49,7 +49,7 @@ static const unsigned int ad7616_oversampling_avail[8] = { > 1, 2, 4, 8, 16, 32, 64, 128, > }; > > -static int ad7606_reset(struct ad7606_state *st) > +int ad7606_reset(struct ad7606_state *st) > { > if (st->gpio_reset) { > gpiod_set_value(st->gpio_reset, 1); > @@ -60,6 +60,7 @@ static int ad7606_reset(struct ad7606_state *st) > > return -ENODEV; > } > +EXPORT_SYMBOL_NS_GPL(ad7606_reset, IIO_AD7606); > > static int ad7606_reg_access(struct iio_dev *indio_dev, > unsigned int reg, > @@ -88,31 +89,6 @@ static int ad7606_read_samples(struct ad7606_state *st) > { > unsigned int num = st->chip_info->num_channels - 1; > u16 *data = st->data; > - int ret; > - > - /* > - * The frstdata signal is set to high while and after reading the sample > - * of the first channel and low for all other channels. This can be used > - * to check that the incoming data is correctly aligned. During normal > - * operation the data should never become unaligned, but some glitch or > - * electrostatic discharge might cause an extra read or clock cycle. > - * Monitoring the frstdata signal allows to recover from such failure > - * situations. > - */ > - > - if (st->gpio_frstdata) { > - ret = st->bops->read_block(st->dev, 1, data); > - if (ret) > - return ret; > - > - if (!gpiod_get_value(st->gpio_frstdata)) { > - ad7606_reset(st); > - return -EIO; > - } > - > - data++; > - num--; > - } > > return st->bops->read_block(st->dev, num, data); > } > diff --git a/drivers/iio/adc/ad7606.h b/drivers/iio/adc/ad7606.h > index 0c6a88cc4695..6649e84d25de 100644 > --- a/drivers/iio/adc/ad7606.h > +++ b/drivers/iio/adc/ad7606.h > @@ -151,6 +151,8 @@ int ad7606_probe(struct device *dev, int irq, void __iomem *base_address, > const char *name, unsigned int id, > const struct ad7606_bus_ops *bops); > > +int ad7606_reset(struct ad7606_state *st); > + > enum ad7606_supported_device_ids { > ID_AD7605_4, > ID_AD7606_8, > diff --git a/drivers/iio/adc/ad7606_par.c b/drivers/iio/adc/ad7606_par.c > index d8408052262e..1f7050297b64 100644 > --- a/drivers/iio/adc/ad7606_par.c > +++ b/drivers/iio/adc/ad7606_par.c > @@ -7,6 +7,7 @@ > > #include <linux/mod_devicetable.h> > #include <linux/module.h> > +#include <linux/gpio/consumer.h> > #include <linux/platform_device.h> > #include <linux/types.h> > #include <linux/err.h> > @@ -21,8 +22,30 @@ static int ad7606_par16_read_block(struct device *dev, > struct iio_dev *indio_dev = dev_get_drvdata(dev); > struct ad7606_state *st = iio_priv(indio_dev); > > - insw((unsigned long)st->base_address, buf, count); > > + /* > + * On the parallel interface, the frstdata signal is set to high while > + * and after reading the sample of the first channel and low for all > + * other channels. This can be used to check that the incoming data is > + * correctly aligned. During normal operation the data should never > + * become unaligned, but some glitch or electrostatic discharge might > + * cause an extra read or clock cycle. Monitoring the frstdata signal > + * allows to recover from such failure situations. > + */ > + int num = count; > + u16 *_buf = buf; > + > + if (st->gpio_frstdata) { > + insw((unsigned long)st->base_address, _buf, 1); > + if (!gpiod_get_value(st->gpio_frstdata)) { > + ad7606_reset(st); > + return -EIO; > + } > + _buf++; > + num--; > + } > + insw((unsigned long)st->base_address, _buf, num) > +; Seems this slipped onto the next line. Make sure to run checkpatch which I would have thought would catch this. > return 0; > } > > @@ -35,8 +58,28 @@ static int ad7606_par8_read_block(struct device *dev, > { > struct iio_dev *indio_dev = dev_get_drvdata(dev); > struct ad7606_state *st = iio_priv(indio_dev); > - > - insb((unsigned long)st->base_address, buf, count * 2); > + /* > + * On the parallel interface, the frstdata signal is set to high while > + * and after reading the sample of the first channel and low for all > + * other channels. This can be used to check that the incoming data is > + * correctly aligned. During normal operation the data should never > + * become unaligned, but some glitch or electrostatic discharge might > + * cause an extra read or clock cycle. Monitoring the frstdata signal > + * allows to recover from such failure situations. > + */ > + int num = count; > + u16 *_buf = buf; > + > + if (st->gpio_frstdata) { > + insb((unsigned long)st->base_address, _buf, 2); > + if (!gpiod_get_value(st->gpio_frstdata)) { > + ad7606_reset(st); > + return -EIO; > + } > + _buf++; > + num--; > + } > + insb((unsigned long)st->base_address, _buf, num * 2); > > return 0; > } > > --- > base-commit: 07d4d0bb4a8ddcc463ed599b22f510d5926c2495 > change-id: 20240416-cleanup-ad7606-161e2ed9818b > > Best regards,
