We can simplify the code and get rid of most of the gotos by using
guard(mutex) from cleanup.h.
Signed-off-by: David Lechner <[email protected]>
---
v4 changes: New patch in v4.
drivers/staging/iio/resolver/ad2s1210.c | 157 ++++++++++----------------------
1 file changed, 50 insertions(+), 107 deletions(-)
diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
index c4e1bc22e8b0..c4e0ffa92dc2 100644
--- a/drivers/staging/iio/resolver/ad2s1210.c
+++ b/drivers/staging/iio/resolver/ad2s1210.c
@@ -47,6 +47,7 @@
#include <linux/bitfield.h>
#include <linux/bits.h>
+#include <linux/cleanup.h>
#include <linux/clk.h>
#include <linux/delay.h>
#include <linux/device.h>
@@ -404,11 +405,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
s64 timestamp;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
+
gpiod_set_value(st->sample_gpio, 1);
timestamp = iio_get_time_ns(indio_dev);
/* delay (6 * tck + 20) nano seconds */
udelay(1);
+ gpiod_set_value(st->sample_gpio, 0);
switch (chan->type) {
case IIO_ANGL:
@@ -418,14 +421,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
ret = ad2s1210_set_mode(st, MOD_VEL);
break;
default:
- ret = -EINVAL;
- break;
+ return -EINVAL;
}
if (ret < 0)
- goto error_ret;
+ return ret;
ret = spi_read(st->sdev, &st->sample, 3);
if (ret < 0)
- goto error_ret;
+ return ret;
switch (chan->type) {
case IIO_ANGL:
@@ -437,17 +439,11 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
ret = IIO_VAL_INT;
break;
default:
- ret = -EINVAL;
- break;
+ return -EINVAL;
}
ad2s1210_push_events(indio_dev, st->sample.fault, timestamp);
-error_ret:
- gpiod_set_value(st->sample_gpio, 0);
- /* delay (2 * tck + 20) nano seconds */
- udelay(1);
- mutex_unlock(&st->lock);
return ret;
}
@@ -455,11 +451,9 @@ static int ad2s1210_get_hysteresis(struct ad2s1210_state *st, int *val)
{
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
ret = regmap_test_bits(st->regmap, AD2S1210_REG_CONTROL,
AD2S1210_ENABLE_HYSTERESIS);
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -469,15 +463,10 @@ static int ad2s1210_get_hysteresis(struct ad2s1210_state *st, int *val)
static int ad2s1210_set_hysteresis(struct ad2s1210_state *st, int val)
{
- int ret;
-
- mutex_lock(&st->lock);
- ret = regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
- AD2S1210_ENABLE_HYSTERESIS,
- val ? AD2S1210_ENABLE_HYSTERESIS : 0);
- mutex_unlock(&st->lock);
-
- return ret;
+ guard(mutex)(&st->lock);
+ return regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
+ AD2S1210_ENABLE_HYSTERESIS,
+ val ? AD2S1210_ENABLE_HYSTERESIS : 0);
}
static int ad2s1210_get_phase_lock_range(struct ad2s1210_state *st,
@@ -485,11 +474,9 @@ static int ad2s1210_get_phase_lock_range(struct ad2s1210_state *st,
{
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
ret = regmap_test_bits(st->regmap, AD2S1210_REG_CONTROL,
AD2S1210_PHASE_LOCK_RANGE_44);
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -509,7 +496,7 @@ static int ad2s1210_get_phase_lock_range(struct ad2s1210_state *st,
static int ad2s1210_set_phase_lock_range(struct ad2s1210_state *st,
int val, int val2)
{
- int deg, ret;
+ int deg;
/* convert radians to degrees - only two allowable values */
if (val == PHASE_44_DEG_TO_RAD_INT && val2 == PHASE_44_DEG_TO_RAD_MICRO)
@@ -520,12 +507,10 @@ static int ad2s1210_set_phase_lock_range(struct ad2s1210_state *st,
else
return -EINVAL;
- mutex_lock(&st->lock);
- ret = regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
- AD2S1210_PHASE_LOCK_RANGE_44,
- deg == 44 ? AD2S1210_PHASE_LOCK_RANGE_44 : 0);
- mutex_unlock(&st->lock);
- return ret;
+ guard(mutex)(&st->lock);
+ return regmap_update_bits(st->regmap, AD2S1210_REG_CONTROL,
+ AD2S1210_PHASE_LOCK_RANGE_44,
+ deg == 44 ? AD2S1210_PHASE_LOCK_RANGE_44 : 0);
}
/* map resolution to microradians/LSB for LOT registers */
@@ -542,10 +527,8 @@ static int ad2s1210_get_voltage_threshold(struct ad2s1210_state *st,
unsigned int reg_val;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
ret = regmap_read(st->regmap, reg, ®_val);
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -557,15 +540,11 @@ static int ad2s1210_set_voltage_threshold(struct ad2s1210_state *st,
unsigned int reg, int val)
{
unsigned int reg_val;
- int ret;
reg_val = val / THRESHOLD_MILLIVOLT_PER_LSB;
- mutex_lock(&st->lock);
- ret = regmap_write(st->regmap, reg, reg_val);
- mutex_unlock(&st->lock);
-
- return ret;
+ guard(mutex)(&st->lock);
+ return regmap_write(st->regmap, reg, reg_val);
}
static int ad2s1210_get_lot_high_threshold(struct ad2s1210_state *st,
@@ -574,10 +553,8 @@ static int ad2s1210_get_lot_high_threshold(struct ad2s1210_state *st,
unsigned int reg_val;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
ret = regmap_read(st->regmap, AD2S1210_REG_LOT_HIGH_THRD, ®_val);
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -596,18 +573,18 @@ static int ad2s1210_set_lot_high_threshold(struct ad2s1210_state *st,
if (val != 0)
return -EINVAL;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
/*
* We need to read both high and low registers first so we can preserve
* the hysteresis.
*/
ret = regmap_read(st->regmap, AD2S1210_REG_LOT_HIGH_THRD, &high_reg_val);
if (ret < 0)
- goto error_ret;
+ return ret;
ret = regmap_read(st->regmap, AD2S1210_REG_LOT_LOW_THRD, &low_reg_val);
if (ret < 0)
- goto error_ret;
+ return ret;
hysteresis = high_reg_val - low_reg_val;
high_reg_val = val2 / ad2s1210_lot_threshold_urad_per_lsb[st->resolution];
@@ -615,14 +592,9 @@ static int ad2s1210_set_lot_high_threshold(struct ad2s1210_state *st,
ret = regmap_write(st->regmap, AD2S1210_REG_LOT_HIGH_THRD, high_reg_val);
if (ret < 0)
- goto error_ret;
-
- ret = regmap_write(st->regmap, AD2S1210_REG_LOT_LOW_THRD, low_reg_val);
-
-error_ret:
- mutex_unlock(&st->lock);
+ return ret;
- return ret;
+ return regmap_write(st->regmap, AD2S1210_REG_LOT_LOW_THRD, low_reg_val);
}
static int ad2s1210_get_lot_low_threshold(struct ad2s1210_state *st,
@@ -631,16 +603,13 @@ static int ad2s1210_get_lot_low_threshold(struct ad2s1210_state *st,
unsigned int high_reg_val, low_reg_val;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
+
ret = regmap_read(st->regmap, AD2S1210_REG_LOT_HIGH_THRD, &high_reg_val);
if (ret < 0)
- goto error_ret;
+ return ret;
ret = regmap_read(st->regmap, AD2S1210_REG_LOT_LOW_THRD, &low_reg_val);
-
-error_ret:
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -663,18 +632,14 @@ static int ad2s1210_set_lot_low_threshold(struct ad2s1210_state *st,
hysteresis = val2 / ad2s1210_lot_threshold_urad_per_lsb[st->resolution];
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
+
ret = regmap_read(st->regmap, AD2S1210_REG_LOT_HIGH_THRD, ®_val);
if (ret < 0)
- goto error_ret;
+ return ret;
- ret = regmap_write(st->regmap, AD2S1210_REG_LOT_LOW_THRD,
+ return regmap_write(st->regmap, AD2S1210_REG_LOT_LOW_THRD,
reg_val - hysteresis);
-
-error_ret:
- mutex_unlock(&st->lock);
-
- return ret;
}
static int ad2s1210_get_excitation_frequency(struct ad2s1210_state *st, int *val)
@@ -682,31 +647,23 @@ static int ad2s1210_get_excitation_frequency(struct ad2s1210_state *st, int *val
unsigned int reg_val;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
+
ret = regmap_read(st->regmap, AD2S1210_REG_EXCIT_FREQ, ®_val);
if (ret < 0)
- goto error_ret;
+ return ret;
*val = reg_val * st->clkin_hz / (1 << 15);
- ret = IIO_VAL_INT;
-
-error_ret:
- mutex_unlock(&st->lock);
- return ret;
+ return IIO_VAL_INT;
}
static int ad2s1210_set_excitation_frequency(struct ad2s1210_state *st, int val)
{
- int ret;
-
if (val < AD2S1210_MIN_EXCIT || val > AD2S1210_MAX_EXCIT)
return -EINVAL;
- mutex_lock(&st->lock);
- ret = ad2s1210_reinit_excitation_frequency(st, val);
- mutex_unlock(&st->lock);
-
- return ret;
+ guard(mutex)(&st->lock);
+ return ad2s1210_reinit_excitation_frequency(st, val);
}
static const int ad2s1210_velocity_scale[] = {
@@ -982,10 +939,8 @@ static ssize_t event_attr_voltage_reg_show(struct device *dev,
unsigned int value;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
ret = regmap_read(st->regmap, iattr->address, &value);
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -1005,11 +960,9 @@ static ssize_t event_attr_voltage_reg_store(struct device *dev,
if (ret)
return -EINVAL;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
ret = regmap_write(st->regmap, iattr->address,
data / THRESHOLD_MILLIVOLT_PER_LSB);
- mutex_unlock(&st->lock);
-
if (ret < 0)
return ret;
@@ -1083,7 +1036,7 @@ static int ad2s1210_initial(struct ad2s1210_state *st)
unsigned int data;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
/* Use default config register value plus resolution from devicetree. */
data = FIELD_PREP(AD2S1210_PHASE_LOCK_RANGE_44, 1);
@@ -1093,13 +1046,9 @@ static int ad2s1210_initial(struct ad2s1210_state *st)
ret = regmap_write(st->regmap, AD2S1210_REG_CONTROL, data);
if (ret < 0)
- goto error_ret;
-
- ret = ad2s1210_reinit_excitation_frequency(st, AD2S1210_DEF_EXCIT);
+ return ret;
-error_ret:
- mutex_unlock(&st->lock);
- return ret;
+ return ad2s1210_reinit_excitation_frequency(st, AD2S1210_DEF_EXCIT);
}
static int ad2s1210_read_label(struct iio_dev *indio_dev,
@@ -1243,18 +1192,13 @@ static int ad2s1210_debugfs_reg_access(struct iio_dev *indio_dev,
unsigned int *readval)
{
struct ad2s1210_state *st = iio_priv(indio_dev);
- int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
if (readval)
- ret = regmap_read(st->regmap, reg, readval);
- else
- ret = regmap_write(st->regmap, reg, writeval);
-
- mutex_unlock(&st->lock);
+ return regmap_read(st->regmap, reg, readval);
- return ret;
+ return regmap_write(st->regmap, reg, writeval);
}
static irqreturn_t ad2s1210_trigger_handler(int irq, void *p)
@@ -1265,7 +1209,7 @@ static irqreturn_t ad2s1210_trigger_handler(int irq, void *p)
size_t chan = 0;
int ret;
- mutex_lock(&st->lock);
+ guard(mutex)(&st->lock);
memset(&st->scan, 0, sizeof(st->scan));
gpiod_set_value(st->sample_gpio, 1);
@@ -1299,7 +1243,6 @@ static irqreturn_t ad2s1210_trigger_handler(int irq, void *p)
error_ret:
gpiod_set_value(st->sample_gpio, 0);
- mutex_unlock(&st->lock);
iio_trigger_notify_done(indio_dev->trig);
return IRQ_HANDLED;
--
2.42.0
On Thu, 5 Oct 2023 19:50:34 -0500
David Lechner <[email protected]> wrote:
> We can simplify the code and get rid of most of the gotos by using
> guard(mutex) from cleanup.h.
You could consider scoped_guard() for a few cases in here, but perhaps
it's better to be consistent and always use the guard() version.
There is a small timing question wrt to the gpio manipulation inline.
>
> Signed-off-by: David Lechner <[email protected]>
> ---
>
> v4 changes: New patch in v4.
>
> drivers/staging/iio/resolver/ad2s1210.c | 157 ++++++++++----------------------
> 1 file changed, 50 insertions(+), 107 deletions(-)
>
> diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> index c4e1bc22e8b0..c4e0ffa92dc2 100644
> --- a/drivers/staging/iio/resolver/ad2s1210.c
> +++ b/drivers/staging/iio/resolver/ad2s1210.c
> @@ -47,6 +47,7 @@
>
> #include <linux/bitfield.h>
> #include <linux/bits.h>
> +#include <linux/cleanup.h>
> #include <linux/clk.h>
> #include <linux/delay.h>
> #include <linux/device.h>
> @@ -404,11 +405,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> s64 timestamp;
> int ret;
>
> - mutex_lock(&st->lock);
> + guard(mutex)(&st->lock);
> +
> gpiod_set_value(st->sample_gpio, 1);
> timestamp = iio_get_time_ns(indio_dev);
> /* delay (6 * tck + 20) nano seconds */
> udelay(1);
> + gpiod_set_value(st->sample_gpio, 0);
>
> switch (chan->type) {
> case IIO_ANGL:
> @@ -418,14 +421,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> ret = ad2s1210_set_mode(st, MOD_VEL);
> break;
> default:
> - ret = -EINVAL;
> - break;
> + return -EINVAL;
> }
> if (ret < 0)
> - goto error_ret;
> + return ret;
> ret = spi_read(st->sdev, &st->sample, 3);
> if (ret < 0)
> - goto error_ret;
> + return ret;
>
> switch (chan->type) {
> case IIO_ANGL:
> @@ -437,17 +439,11 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> ret = IIO_VAL_INT;
> break;
> default:
> - ret = -EINVAL;
> - break;
> + return -EINVAL;
> }
>
> ad2s1210_push_events(indio_dev, st->sample.fault, timestamp);
>
> -error_ret:
> - gpiod_set_value(st->sample_gpio, 0);
> - /* delay (2 * tck + 20) nano seconds */
> - udelay(1);
Dropping this delay isn't obviously safe (though it probably is given stuff done before we exit).
I assume there are no rules on holding the gpio down for the register read.
If nothing else I think the patch description needs to made an argument for why it is fine.
> - mutex_unlock(&st->lock);
> return ret;
> }
>
On Tue, Oct 10, 2023 at 11:17 AM Jonathan Cameron <[email protected]> wrote:
>
> On Thu, 5 Oct 2023 19:50:34 -0500
> David Lechner <[email protected]> wrote:
>
> > We can simplify the code and get rid of most of the gotos by using
> > guard(mutex) from cleanup.h.
> You could consider scoped_guard() for a few cases in here, but perhaps
> it's better to be consistent and always use the guard() version.
Yes, there it doesn't look like there are any cases where there is any
long-running operation that could be done after unlocking the mutex,
so I went with the simpler approach everywhere.
>
> There is a small timing question wrt to the gpio manipulation inline.
>
> >
> > Signed-off-by: David Lechner <[email protected]>
> > ---
> >
> > v4 changes: New patch in v4.
> >
> > drivers/staging/iio/resolver/ad2s1210.c | 157 ++++++++++----------------------
> > 1 file changed, 50 insertions(+), 107 deletions(-)
> >
> > diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> > index c4e1bc22e8b0..c4e0ffa92dc2 100644
> > --- a/drivers/staging/iio/resolver/ad2s1210.c
> > +++ b/drivers/staging/iio/resolver/ad2s1210.c
> > @@ -47,6 +47,7 @@
> >
> > #include <linux/bitfield.h>
> > #include <linux/bits.h>
> > +#include <linux/cleanup.h>
> > #include <linux/clk.h>
> > #include <linux/delay.h>
> > #include <linux/device.h>
> > @@ -404,11 +405,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> > s64 timestamp;
> > int ret;
> >
> > - mutex_lock(&st->lock);
> > + guard(mutex)(&st->lock);
> > +
> > gpiod_set_value(st->sample_gpio, 1);
> > timestamp = iio_get_time_ns(indio_dev);
> > /* delay (6 * tck + 20) nano seconds */
> > udelay(1);
> > + gpiod_set_value(st->sample_gpio, 0);
> >
> > switch (chan->type) {
> > case IIO_ANGL:
> > @@ -418,14 +421,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> > ret = ad2s1210_set_mode(st, MOD_VEL);
> > break;
> > default:
> > - ret = -EINVAL;
> > - break;
> > + return -EINVAL;
> > }
> > if (ret < 0)
> > - goto error_ret;
> > + return ret;
> > ret = spi_read(st->sdev, &st->sample, 3);
> > if (ret < 0)
> > - goto error_ret;
> > + return ret;
> >
> > switch (chan->type) {
> > case IIO_ANGL:
> > @@ -437,17 +439,11 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> > ret = IIO_VAL_INT;
> > break;
> > default:
> > - ret = -EINVAL;
> > - break;
> > + return -EINVAL;
> > }
> >
> > ad2s1210_push_events(indio_dev, st->sample.fault, timestamp);
> >
> > -error_ret:
> > - gpiod_set_value(st->sample_gpio, 0);
> > - /* delay (2 * tck + 20) nano seconds */
> > - udelay(1);
>
> Dropping this delay isn't obviously safe (though it probably is given stuff done before we exit).
> I assume there are no rules on holding the gpio down for the register read.
Correct. The SAMPLE gpio only needs to be held for a short time (~350
nanoseconds) to latch in the current values, then it doesn't matter
when it is released. (Figure 35 in datasheet)
>
> If nothing else I think the patch description needs to made an argument for why it is fine.
The longest possible delay needed after releasing the SAMPLE line
before reasserting is ~350 nanoseconds. Is there a rule of thumb for
deciding when there are enough instructions that no processor could
execute them faster than this vs. when we should add an explicit
delay?
I think I will consider adding a patch in the next round to refactor
the SAMPLE toggle to a separate function so we can be sure it is
handled the same in all cases.
>
> > - mutex_unlock(&st->lock);
> > return ret;
> > }
> >
On Tue, 10 Oct 2023 12:40:03 -0500
David Lechner <[email protected]> wrote:
> On Tue, Oct 10, 2023 at 11:17 AM Jonathan Cameron <[email protected]> wrote:
> >
> > On Thu, 5 Oct 2023 19:50:34 -0500
> > David Lechner <[email protected]> wrote:
> >
> > > We can simplify the code and get rid of most of the gotos by using
> > > guard(mutex) from cleanup.h.
> > You could consider scoped_guard() for a few cases in here, but perhaps
> > it's better to be consistent and always use the guard() version.
>
> Yes, there it doesn't look like there are any cases where there is any
> long-running operation that could be done after unlocking the mutex,
> so I went with the simpler approach everywhere.
>
> >
> > There is a small timing question wrt to the gpio manipulation inline.
> >
> > >
> > > Signed-off-by: David Lechner <[email protected]>
> > > ---
> > >
> > > v4 changes: New patch in v4.
> > >
> > > drivers/staging/iio/resolver/ad2s1210.c | 157 ++++++++++----------------------
> > > 1 file changed, 50 insertions(+), 107 deletions(-)
> > >
> > > diff --git a/drivers/staging/iio/resolver/ad2s1210.c b/drivers/staging/iio/resolver/ad2s1210.c
> > > index c4e1bc22e8b0..c4e0ffa92dc2 100644
> > > --- a/drivers/staging/iio/resolver/ad2s1210.c
> > > +++ b/drivers/staging/iio/resolver/ad2s1210.c
> > > @@ -47,6 +47,7 @@
> > >
> > > #include <linux/bitfield.h>
> > > #include <linux/bits.h>
> > > +#include <linux/cleanup.h>
> > > #include <linux/clk.h>
> > > #include <linux/delay.h>
> > > #include <linux/device.h>
> > > @@ -404,11 +405,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> > > s64 timestamp;
> > > int ret;
> > >
> > > - mutex_lock(&st->lock);
> > > + guard(mutex)(&st->lock);
> > > +
> > > gpiod_set_value(st->sample_gpio, 1);
> > > timestamp = iio_get_time_ns(indio_dev);
> > > /* delay (6 * tck + 20) nano seconds */
> > > udelay(1);
> > > + gpiod_set_value(st->sample_gpio, 0);
> > >
> > > switch (chan->type) {
> > > case IIO_ANGL:
> > > @@ -418,14 +421,13 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> > > ret = ad2s1210_set_mode(st, MOD_VEL);
> > > break;
> > > default:
> > > - ret = -EINVAL;
> > > - break;
> > > + return -EINVAL;
> > > }
> > > if (ret < 0)
> > > - goto error_ret;
> > > + return ret;
> > > ret = spi_read(st->sdev, &st->sample, 3);
> > > if (ret < 0)
> > > - goto error_ret;
> > > + return ret;
> > >
> > > switch (chan->type) {
> > > case IIO_ANGL:
> > > @@ -437,17 +439,11 @@ static int ad2s1210_single_conversion(struct iio_dev *indio_dev,
> > > ret = IIO_VAL_INT;
> > > break;
> > > default:
> > > - ret = -EINVAL;
> > > - break;
> > > + return -EINVAL;
> > > }
> > >
> > > ad2s1210_push_events(indio_dev, st->sample.fault, timestamp);
> > >
> > > -error_ret:
> > > - gpiod_set_value(st->sample_gpio, 0);
> > > - /* delay (2 * tck + 20) nano seconds */
> > > - udelay(1);
> >
> > Dropping this delay isn't obviously safe (though it probably is given stuff done before we exit).
> > I assume there are no rules on holding the gpio down for the register read.
>
> Correct. The SAMPLE gpio only needs to be held for a short time (~350
> nanoseconds) to latch in the current values, then it doesn't matter
> when it is released. (Figure 35 in datasheet)
>
> >
> > If nothing else I think the patch description needs to made an argument for why it is fine.
>
> The longest possible delay needed after releasing the SAMPLE line
> before reasserting is ~350 nanoseconds. Is there a rule of thumb for
> deciding when there are enough instructions that no processor could
> execute them faster than this vs. when we should add an explicit
> delay?
Almost always use an explicit delay as then we don't have to think about it.
>
> I think I will consider adding a patch in the next round to refactor
> the SAMPLE toggle to a separate function so we can be sure it is
> handled the same in all cases.
Sounds good.
Jonathan
>
> >
> > > - mutex_unlock(&st->lock);
> > > return ret;
> > > }
> > >