Message ID | 20200722155103.979802-19-jic23@kernel.org (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | IIO: Fused set 1 and 2 of timestamp alignment fixes | expand |
On Wed, Jul 22, 2020 at 6:53 PM Jonathan Cameron <jic23@kernel.org> wrote: > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > We should not be assuming that we are reading a sequence of > registers as here we are doing a read of a lot of data from > a single register address. > - result = regmap_bulk_read(st->map, st->reg->fifo_r_w, > - st->data, bytes_per_datum); > + result = regmap_noinc_read(st->map, st->reg->fifo_r_w, > + st->data, bytes_per_datum); I don't know the difference between these APIs, but AFAIU in this case we always ask for a minimum data (like one item of 2 bytes or so) per access. Because registers are defined like 16-bit wide we are fine. Is that correct?
On Thu, 23 Jul 2020 15:15:46 +0300 Andy Shevchenko <andy.shevchenko@gmail.com> wrote: > On Wed, Jul 22, 2020 at 6:53 PM Jonathan Cameron <jic23@kernel.org> wrote: > > > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > > > We should not be assuming that we are reading a sequence of > > registers as here we are doing a read of a lot of data from > > a single register address. > > > - result = regmap_bulk_read(st->map, st->reg->fifo_r_w, > > - st->data, bytes_per_datum); > > + result = regmap_noinc_read(st->map, st->reg->fifo_r_w, > > + st->data, bytes_per_datum); > > I don't know the difference between these APIs, but AFAIU in this case > we always ask for a minimum data (like one item of 2 bytes or so) per > access. Because registers are defined like 16-bit wide we are fine. Is > that correct? Yes. There is only really a different in these two APIs if caching is enabled in regmap. Conceptually noinc is repeated reading of the same register, whilst build_read reads a bunch of registers starting at this location. If any of them happen to be cacheable, regmap_bulk_read will update the cached value for any registers it happens to read. In this particular case that would be incorrect because the hardware is not doing any auto increment of the address during repeated reads, it's just reading the same register lots of times. Jonathan
Hi Jonathan, perfect. Thanks for the fix, JB Reviewed-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com> From: linux-iio-owner@vger.kernel.org <linux-iio-owner@vger.kernel.org> on behalf of Jonathan Cameron <jic23@kernel.org> Sent: Wednesday, July 22, 2020 17:50 To: linux-iio@vger.kernel.org <linux-iio@vger.kernel.org> Cc: Andy Shevchenko <andy.shevchenko@gmail.com>; Lars-Peter Clausen <lars@metafoo.de>; Peter Meerwald <pmeerw@pmeerw.net>; Jonathan Cameron <Jonathan.Cameron@huawei.com>; Jean-Baptiste Maneyrol <JManeyrol@invensense.com> Subject: [PATCH v3 18/27] iio:imu:inv_mpu6050: Use regmap_noinc_read for fifo reads. CAUTION: This email originated from outside of the organization. Please make sure the sender is who they say they are and do not click links or open attachments unless you recognize the sender and know the content is safe. From: Jonathan Cameron <Jonathan.Cameron@huawei.com> We should not be assuming that we are reading a sequence of registers as here we are doing a read of a lot of data from a single register address. Suggested-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> --- drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c index d8e6b88ddffc..45c37525c2f1 100644 --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c @@ -179,8 +179,8 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p) nb = fifo_count / bytes_per_datum; inv_mpu6050_update_period(st, pf->timestamp, nb); for (i = 0; i < nb; ++i) { - result = regmap_bulk_read(st->map, st->reg->fifo_r_w, - st->data, bytes_per_datum); + result = regmap_noinc_read(st->map, st->reg->fifo_r_w, + st->data, bytes_per_datum); if (result) goto flush_fifo; /* skip first samples if needed */
On Fri, 24 Jul 2020 08:29:56 +0000 Jean-Baptiste Maneyrol <JManeyrol@invensense.com> wrote: > Hi Jonathan, > > perfect. > > Thanks for the fix, > JB > > Reviewed-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com> > > > From: linux-iio-owner@vger.kernel.org <linux-iio-owner@vger.kernel.org> on behalf of Jonathan Cameron <jic23@kernel.org> > Sent: Wednesday, July 22, 2020 17:50 > To: linux-iio@vger.kernel.org <linux-iio@vger.kernel.org> > Cc: Andy Shevchenko <andy.shevchenko@gmail.com>; Lars-Peter Clausen <lars@metafoo.de>; Peter Meerwald <pmeerw@pmeerw.net>; Jonathan Cameron <Jonathan.Cameron@huawei.com>; Jean-Baptiste Maneyrol <JManeyrol@invensense.com> > Subject: [PATCH v3 18/27] iio:imu:inv_mpu6050: Use regmap_noinc_read for fifo reads. > > CAUTION: This email originated from outside of the organization. Please make sure the sender is who they say they are and do not click links or open attachments unless you recognize the sender and know the content is safe. > > From: Jonathan Cameron <Jonathan.Cameron@huawei.com> > > We should not be assuming that we are reading a sequence of > registers as here we are doing a read of a lot of data from > a single register address. > > Suggested-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> Applied to the togreg branch of iio.git. I've explicitly added that this one isn't marked for stable as it doesn't actually have any affect beyond being semantically correct. thanks, Jonathan > --- > drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c > index d8e6b88ddffc..45c37525c2f1 100644 > --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c > +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c > @@ -179,8 +179,8 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p) > nb = fifo_count / bytes_per_datum; > inv_mpu6050_update_period(st, pf->timestamp, nb); > for (i = 0; i < nb; ++i) { > - result = regmap_bulk_read(st->map, st->reg->fifo_r_w, > - st->data, bytes_per_datum); > + result = regmap_noinc_read(st->map, st->reg->fifo_r_w, > + st->data, bytes_per_datum); > if (result) > goto flush_fifo; > /* skip first samples if needed */
diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c index d8e6b88ddffc..45c37525c2f1 100644 --- a/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c +++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_ring.c @@ -179,8 +179,8 @@ irqreturn_t inv_mpu6050_read_fifo(int irq, void *p) nb = fifo_count / bytes_per_datum; inv_mpu6050_update_period(st, pf->timestamp, nb); for (i = 0; i < nb; ++i) { - result = regmap_bulk_read(st->map, st->reg->fifo_r_w, - st->data, bytes_per_datum); + result = regmap_noinc_read(st->map, st->reg->fifo_r_w, + st->data, bytes_per_datum); if (result) goto flush_fifo; /* skip first samples if needed */