On Mon, 24 Jun 2024 15:33:01 +0200 Guillaume Stols <gstols@xxxxxxxxxxxx> wrote: > On 6/23/24 17:54, Jonathan Cameron wrote: > > 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 > > It completely prevents the driver to work when adi, first-data > (optional) is defined in the DT. > > So I guess anyone having the driver working with the serial interface > right now did not define frstdata in the DT. > > However, for someone new that sets adi, first-data in the DT, it is not > very straightforward to spot where the issue is. Thanks for the info. Could you send a v2 with that included in the patch description and a suitable fixes tag. Plus tidy up the extra linebreak noted below. Thanks, 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,
