Re: [PATCH v4 1/3] counter: 104-quad-8: Add lock guards - generic interface

From: William Breathitt Gray
Date: Sun Mar 15 2020 - 10:39:47 EST

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In reply to: Jonathan Cameron: "Re: [PATCH v4 1/3] counter: 104-quad-8: Add lock guards - generic interface"
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On Sun, Mar 15, 2020 at 02:29:16PM +0000, Jonathan Cameron wrote:
> On Sun, 15 Mar 2020 10:06:56 -0400
> William Breathitt Gray <vilhelm.gray@xxxxxxxxx> wrote:
>
> > On Sun, Mar 15, 2020 at 12:09:04PM +0000, Jonathan Cameron wrote:
> > > On Fri, 13 Mar 2020 12:51:02 -0400
> > > William Breathitt Gray <vilhelm.gray@xxxxxxxxx> wrote:
> > >
> > > > On Fri, Mar 13, 2020 at 05:30:58PM +0530, Syed Nayyar Waris wrote:
> > > > > Add lock protection from race conditions to 104-quad-8 counter driver
> > > > > generic interface code changes. There is no IRQ handling so spin_lock
> > > > > calls are used for protection.
> > > > >
> > > > > Fixes: f1d8a071d45b ("counter: 104-quad-8: Add Generic Counter interface support")
> > > > >
> > > > > Signed-off-by: Syed Nayyar Waris <syednwaris@xxxxxxxxx>
> > > >
> > > > Thanks Syed, this version looks good to me.
> > > >
> > > > Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
> > > >
> > > > Jonathan, if you have no objections please pick up this series.
> > >
> > > One question. Why not a mutex? If there aren't an interrupts involved
> > > that would normally be preferred.
> > >
> > > Jonathan
> >
> > I don't think a mutex would be appropriate in this context would it?
> > We're just executing some basic port I/O operations and briefly
> > accessing shared data. Because everything we're doing is very
> > short-term, there's no need for a mutex and adding one just adds the
> > chance of putting the thread to sleep which would be a larger latency
> > than simply waiting for the spinlock to be unlocked.
>
> The mutex should only put the thread to sleep if it's contended.
> Here that should be extremely rare. The question of how large the
> latency is comes down to how contended we might be. I guess we pretty
> much assume we aren't actually contended here unless something weird
> is going on.
>
> >
> > (We don't necessarily need raw_spinlock_t since interrupts aren't
> > involved, but I think the more generic spinlock_t is fine.)
>
> That does allow the RT sleeping spin locks to work fine, but in that
> case might as well just use a mutex in first place and have consistent
> results.
>
> Usually I'd be looking to use a mutex unless it was absolutely required
> to use a spinlock.
>
> I'm not that fussed though and it's very unlikely to make much difference
> in this case. However, the statement in the patch title that we use
> spin_lock as no IRQ calls is very confusing... Note that I'm fairly
> sure spin_lock and raw_spin_lock are currently the same thing unless
> you have applied the RT patch set.
>
> Jonathan

That's a fair point. I don't feel too strongly either way so if Syed
decides to switch to mutex_lock calls, or perhaps remove the confusing
line about IRQs calls in the commit message, I won't object to it.

William Breathitt Gray

>
> >
> > William Breathitt Gray
> >
> > >
> > > >
> > > > William Breathitt Gray
> > > >
> > > > > ---
> > > > > Changes in v4:
> > > > > - Shift review-comments section so that its not saved in commit message.
> > > > > - Add spin_unlock calls for deadlock avoidance.
> > > > > - Change parameters of quad8_preset_register_set.
> > > > > - Few changes related to assignment statements.
> > > > >
> > > > > drivers/counter/104-quad-8.c | 194 +++++++++++++++++++++++++++++++++++--------
> > > > > 1 file changed, 160 insertions(+), 34 deletions(-)
> > > > >
> > > > > diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
> > > > > index 9dab190..88decab 100644
> > > > > --- a/drivers/counter/104-quad-8.c
> > > > > +++ b/drivers/counter/104-quad-8.c
> > > > > @@ -44,6 +44,7 @@ MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");
> > > > > * @base: base port address of the IIO device
> > > > > */
> > > > > struct quad8_iio {
> > > > > + spinlock_t lock;
> > > > > struct counter_device counter;
> > > > > unsigned int fck_prescaler[QUAD8_NUM_COUNTERS];
> > > > > unsigned int preset[QUAD8_NUM_COUNTERS];
> > > > > @@ -123,6 +124,8 @@ static int quad8_read_raw(struct iio_dev *indio_dev,
> > > > > /* Borrow XOR Carry effectively doubles count range */
> > > > > *val = (borrow ^ carry) << 24;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > /* Reset Byte Pointer; transfer Counter to Output Latch */
> > > > > outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_CNTR_OUT,
> > > > > base_offset + 1);
> > > > > @@ -130,6 +133,8 @@ static int quad8_read_raw(struct iio_dev *indio_dev,
> > > > > for (i = 0; i < 3; i++)
> > > > > *val |= (unsigned int)inb(base_offset) << (8 * i);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return IIO_VAL_INT;
> > > > > case IIO_CHAN_INFO_ENABLE:
> > > > > *val = priv->ab_enable[chan->channel];
> > > > > @@ -160,6 +165,8 @@ static int quad8_write_raw(struct iio_dev *indio_dev,
> > > > > if ((unsigned int)val > 0xFFFFFF)
> > > > > return -EINVAL;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > /* Reset Byte Pointer */
> > > > > outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);
> > > > >
> > > > > @@ -183,12 +190,16 @@ static int quad8_write_raw(struct iio_dev *indio_dev,
> > > > > /* Reset Error flag */
> > > > > outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, base_offset + 1);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > case IIO_CHAN_INFO_ENABLE:
> > > > > /* only boolean values accepted */
> > > > > if (val < 0 || val > 1)
> > > > > return -EINVAL;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->ab_enable[chan->channel] = val;
> > > > >
> > > > > ior_cfg = val | priv->preset_enable[chan->channel] << 1;
> > > > > @@ -196,11 +207,18 @@ static int quad8_write_raw(struct iio_dev *indio_dev,
> > > > > /* Load I/O control configuration */
> > > > > outb(QUAD8_CTR_IOR | ior_cfg, base_offset + 1);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > case IIO_CHAN_INFO_SCALE:
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > /* Quadrature scaling only available in quadrature mode */
> > > > > - if (!priv->quadrature_mode[chan->channel] && (val2 || val != 1))
> > > > > + if (!priv->quadrature_mode[chan->channel] &&
> > > > > + (val2 || val != 1)) {
> > > > > + spin_unlock(&priv->lock);
> > > > > return -EINVAL;
> > > > > + }
> > > > >
> > > > > /* Only three gain states (1, 0.5, 0.25) */
> > > > > if (val == 1 && !val2)
> > > > > @@ -214,11 +232,15 @@ static int quad8_write_raw(struct iio_dev *indio_dev,
> > > > > priv->quadrature_scale[chan->channel] = 2;
> > > > > break;
> > > > > default:
> > > > > + spin_unlock(&priv->lock);
> > > > > return -EINVAL;
> > > > > }
> > > > > - else
> > > > > + else {
> > > > > + spin_unlock(&priv->lock);
> > > > > return -EINVAL;
> > > > > + }
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -255,6 +277,8 @@ static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
> > > > > if (preset > 0xFFFFFF)
> > > > > return -EINVAL;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->preset[chan->channel] = preset;
> > > > >
> > > > > /* Reset Byte Pointer */
> > > > > @@ -264,6 +288,8 @@ static ssize_t quad8_write_preset(struct iio_dev *indio_dev, uintptr_t private,
> > > > > for (i = 0; i < 3; i++)
> > > > > outb(preset >> (8 * i), base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return len;
> > > > > }
> > > > >
> > > > > @@ -293,6 +319,8 @@ static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
> > > > > /* Preset enable is active low in Input/Output Control register */
> > > > > preset_enable = !preset_enable;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->preset_enable[chan->channel] = preset_enable;
> > > > >
> > > > > ior_cfg = priv->ab_enable[chan->channel] |
> > > > > @@ -301,6 +329,8 @@ static ssize_t quad8_write_set_to_preset_on_index(struct iio_dev *indio_dev,
> > > > > /* Load I/O control configuration to Input / Output Control Register */
> > > > > outb(QUAD8_CTR_IOR | ior_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return len;
> > > > > }
> > > > >
> > > > > @@ -358,6 +388,8 @@ static int quad8_set_count_mode(struct iio_dev *indio_dev,
> > > > > unsigned int mode_cfg = cnt_mode << 1;
> > > > > const int base_offset = priv->base + 2 * chan->channel + 1;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->count_mode[chan->channel] = cnt_mode;
> > > > >
> > > > > /* Add quadrature mode configuration */
> > > > > @@ -367,6 +399,8 @@ static int quad8_set_count_mode(struct iio_dev *indio_dev,
> > > > > /* Load mode configuration to Counter Mode Register */
> > > > > outb(QUAD8_CTR_CMR | mode_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -394,19 +428,26 @@ static int quad8_set_synchronous_mode(struct iio_dev *indio_dev,
> > > > > const struct iio_chan_spec *chan, unsigned int synchronous_mode)
> > > > > {
> > > > > struct quad8_iio *const priv = iio_priv(indio_dev);
> > > > > - const unsigned int idr_cfg = synchronous_mode |
> > > > > - priv->index_polarity[chan->channel] << 1;
> > > > > const int base_offset = priv->base + 2 * chan->channel + 1;
> > > > > + unsigned int idr_cfg = synchronous_mode;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + idr_cfg |= priv->index_polarity[chan->channel] << 1;
> > > > >
> > > > > /* Index function must be non-synchronous in non-quadrature mode */
> > > > > - if (synchronous_mode && !priv->quadrature_mode[chan->channel])
> > > > > + if (synchronous_mode && !priv->quadrature_mode[chan->channel]) {
> > > > > + spin_unlock(&priv->lock);
> > > > > return -EINVAL;
> > > > > + }
> > > > >
> > > > > priv->synchronous_mode[chan->channel] = synchronous_mode;
> > > > >
> > > > > /* Load Index Control configuration to Index Control Register */
> > > > > outb(QUAD8_CTR_IDR | idr_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -434,8 +475,12 @@ static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
> > > > > const struct iio_chan_spec *chan, unsigned int quadrature_mode)
> > > > > {
> > > > > struct quad8_iio *const priv = iio_priv(indio_dev);
> > > > > - unsigned int mode_cfg = priv->count_mode[chan->channel] << 1;
> > > > > const int base_offset = priv->base + 2 * chan->channel + 1;
> > > > > + unsigned int mode_cfg;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + mode_cfg = priv->count_mode[chan->channel] << 1;
> > > > >
> > > > > if (quadrature_mode)
> > > > > mode_cfg |= (priv->quadrature_scale[chan->channel] + 1) << 3;
> > > > > @@ -453,6 +498,8 @@ static int quad8_set_quadrature_mode(struct iio_dev *indio_dev,
> > > > > /* Load mode configuration to Counter Mode Register */
> > > > > outb(QUAD8_CTR_CMR | mode_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -480,15 +527,20 @@ static int quad8_set_index_polarity(struct iio_dev *indio_dev,
> > > > > const struct iio_chan_spec *chan, unsigned int index_polarity)
> > > > > {
> > > > > struct quad8_iio *const priv = iio_priv(indio_dev);
> > > > > - const unsigned int idr_cfg = priv->synchronous_mode[chan->channel] |
> > > > > - index_polarity << 1;
> > > > > const int base_offset = priv->base + 2 * chan->channel + 1;
> > > > > + unsigned int idr_cfg = index_polarity << 1;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + idr_cfg |= priv->synchronous_mode[chan->channel];
> > > > >
> > > > > priv->index_polarity[chan->channel] = index_polarity;
> > > > >
> > > > > /* Load Index Control configuration to Index Control Register */
> > > > > outb(QUAD8_CTR_IDR | idr_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -589,7 +641,7 @@ static int quad8_signal_read(struct counter_device *counter,
> > > > > static int quad8_count_read(struct counter_device *counter,
> > > > > struct counter_count *count, unsigned long *val)
> > > > > {
> > > > > - const struct quad8_iio *const priv = counter->priv;
> > > > > + struct quad8_iio *const priv = counter->priv;
> > > > > const int base_offset = priv->base + 2 * count->id;
> > > > > unsigned int flags;
> > > > > unsigned int borrow;
> > > > > @@ -603,6 +655,8 @@ static int quad8_count_read(struct counter_device *counter,
> > > > > /* Borrow XOR Carry effectively doubles count range */
> > > > > *val = (unsigned long)(borrow ^ carry) << 24;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > /* Reset Byte Pointer; transfer Counter to Output Latch */
> > > > > outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_CNTR_OUT,
> > > > > base_offset + 1);
> > > > > @@ -610,13 +664,15 @@ static int quad8_count_read(struct counter_device *counter,
> > > > > for (i = 0; i < 3; i++)
> > > > > *val |= (unsigned long)inb(base_offset) << (8 * i);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > static int quad8_count_write(struct counter_device *counter,
> > > > > struct counter_count *count, unsigned long val)
> > > > > {
> > > > > - const struct quad8_iio *const priv = counter->priv;
> > > > > + struct quad8_iio *const priv = counter->priv;
> > > > > const int base_offset = priv->base + 2 * count->id;
> > > > > int i;
> > > > >
> > > > > @@ -624,6 +680,8 @@ static int quad8_count_write(struct counter_device *counter,
> > > > > if (val > 0xFFFFFF)
> > > > > return -EINVAL;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > /* Reset Byte Pointer */
> > > > > outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);
> > > > >
> > > > > @@ -647,6 +705,8 @@ static int quad8_count_write(struct counter_device *counter,
> > > > > /* Reset Error flag */
> > > > > outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, base_offset + 1);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -667,13 +727,13 @@ static enum counter_count_function quad8_count_functions_list[] = {
> > > > > static int quad8_function_get(struct counter_device *counter,
> > > > > struct counter_count *count, size_t *function)
> > > > > {
> > > > > - const struct quad8_iio *const priv = counter->priv;
> > > > > + struct quad8_iio *const priv = counter->priv;
> > > > > const int id = count->id;
> > > > > - const unsigned int quadrature_mode = priv->quadrature_mode[id];
> > > > > - const unsigned int scale = priv->quadrature_scale[id];
> > > > >
> > > > > - if (quadrature_mode)
> > > > > - switch (scale) {
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + if (priv->quadrature_mode[id])
> > > > > + switch (priv->quadrature_scale[id]) {
> > > > > case 0:
> > > > > *function = QUAD8_COUNT_FUNCTION_QUADRATURE_X1;
> > > > > break;
> > > > > @@ -687,6 +747,8 @@ static int quad8_function_get(struct counter_device *counter,
> > > > > else
> > > > > *function = QUAD8_COUNT_FUNCTION_PULSE_DIRECTION;
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -697,10 +759,15 @@ static int quad8_function_set(struct counter_device *counter,
> > > > > const int id = count->id;
> > > > > unsigned int *const quadrature_mode = priv->quadrature_mode + id;
> > > > > unsigned int *const scale = priv->quadrature_scale + id;
> > > > > - unsigned int mode_cfg = priv->count_mode[id] << 1;
> > > > > unsigned int *const synchronous_mode = priv->synchronous_mode + id;
> > > > > - const unsigned int idr_cfg = priv->index_polarity[id] << 1;
> > > > > const int base_offset = priv->base + 2 * id + 1;
> > > > > + unsigned int mode_cfg;
> > > > > + unsigned int idr_cfg;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + mode_cfg = priv->count_mode[id] << 1;
> > > > > + idr_cfg = priv->index_polarity[id] << 1;
> > > > >
> > > > > if (function == QUAD8_COUNT_FUNCTION_PULSE_DIRECTION) {
> > > > > *quadrature_mode = 0;
> > > > > @@ -736,6 +803,8 @@ static int quad8_function_set(struct counter_device *counter,
> > > > > /* Load mode configuration to Counter Mode Register */
> > > > > outb(QUAD8_CTR_CMR | mode_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -852,15 +921,20 @@ static int quad8_index_polarity_set(struct counter_device *counter,
> > > > > {
> > > > > struct quad8_iio *const priv = counter->priv;
> > > > > const size_t channel_id = signal->id - 16;
> > > > > - const unsigned int idr_cfg = priv->synchronous_mode[channel_id] |
> > > > > - index_polarity << 1;
> > > > > const int base_offset = priv->base + 2 * channel_id + 1;
> > > > > + unsigned int idr_cfg = index_polarity << 1;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + idr_cfg |= priv->synchronous_mode[channel_id];
> > > > >
> > > > > priv->index_polarity[channel_id] = index_polarity;
> > > > >
> > > > > /* Load Index Control configuration to Index Control Register */
> > > > > outb(QUAD8_CTR_IDR | idr_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -887,19 +961,26 @@ static int quad8_synchronous_mode_set(struct counter_device *counter,
> > > > > {
> > > > > struct quad8_iio *const priv = counter->priv;
> > > > > const size_t channel_id = signal->id - 16;
> > > > > - const unsigned int idr_cfg = synchronous_mode |
> > > > > - priv->index_polarity[channel_id] << 1;
> > > > > const int base_offset = priv->base + 2 * channel_id + 1;
> > > > > + unsigned int idr_cfg = synchronous_mode;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > + idr_cfg |= priv->index_polarity[channel_id] << 1;
> > > > >
> > > > > /* Index function must be non-synchronous in non-quadrature mode */
> > > > > - if (synchronous_mode && !priv->quadrature_mode[channel_id])
> > > > > + if (synchronous_mode && !priv->quadrature_mode[channel_id]) {
> > > > > + spin_unlock(&priv->lock);
> > > > > return -EINVAL;
> > > > > + }
> > > > >
> > > > > priv->synchronous_mode[channel_id] = synchronous_mode;
> > > > >
> > > > > /* Load Index Control configuration to Index Control Register */
> > > > > outb(QUAD8_CTR_IDR | idr_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -964,6 +1045,8 @@ static int quad8_count_mode_set(struct counter_device *counter,
> > > > > break;
> > > > > }
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->count_mode[count->id] = cnt_mode;
> > > > >
> > > > > /* Set count mode configuration value */
> > > > > @@ -976,6 +1059,8 @@ static int quad8_count_mode_set(struct counter_device *counter,
> > > > > /* Load mode configuration to Counter Mode Register */
> > > > > outb(QUAD8_CTR_CMR | mode_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return 0;
> > > > > }
> > > > >
> > > > > @@ -1017,6 +1102,8 @@ static ssize_t quad8_count_enable_write(struct counter_device *counter,
> > > > > if (err)
> > > > > return err;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->ab_enable[count->id] = ab_enable;
> > > > >
> > > > > ior_cfg = ab_enable | priv->preset_enable[count->id] << 1;
> > > > > @@ -1024,6 +1111,8 @@ static ssize_t quad8_count_enable_write(struct counter_device *counter,
> > > > > /* Load I/O control configuration */
> > > > > outb(QUAD8_CTR_IOR | ior_cfg, base_offset + 1);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return len;
> > > > > }
> > > > >
> > > > > @@ -1052,14 +1141,28 @@ static ssize_t quad8_count_preset_read(struct counter_device *counter,
> > > > > return sprintf(buf, "%u\n", priv->preset[count->id]);
> > > > > }
> > > > >
> > > > > +void quad8_preset_register_set(struct quad8_iio *quad8iio, int id,
> > > > > + unsigned int preset)
> > > > > +{
> > > > > + const unsigned int base_offset = quad8iio->base + 2 * id;
> > > > > + int i;
> > > > > +
> > > > > + quad8iio->preset[id] = preset;
> > > > > +
> > > > > + /* Reset Byte Pointer */
> > > > > + outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);
> > > > > +
> > > > > + /* Set Preset Register */
> > > > > + for (i = 0; i < 3; i++)
> > > > > + outb(preset >> (8 * i), base_offset);
> > > > > +}
> > > > > +
> > > > > static ssize_t quad8_count_preset_write(struct counter_device *counter,
> > > > > struct counter_count *count, void *private, const char *buf, size_t len)
> > > > > {
> > > > > struct quad8_iio *const priv = counter->priv;
> > > > > - const int base_offset = priv->base + 2 * count->id;
> > > > > unsigned int preset;
> > > > > int ret;
> > > > > - int i;
> > > > >
> > > > > ret = kstrtouint(buf, 0, &preset);
> > > > > if (ret)
> > > > > @@ -1069,14 +1172,11 @@ static ssize_t quad8_count_preset_write(struct counter_device *counter,
> > > > > if (preset > 0xFFFFFF)
> > > > > return -EINVAL;
> > > > >
> > > > > - priv->preset[count->id] = preset;
> > > > > + spin_lock(&priv->lock);
> > > > >
> > > > > - /* Reset Byte Pointer */
> > > > > - outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);
> > > > > + quad8_preset_register_set(priv, count->id, preset);
> > > > >
> > > > > - /* Set Preset Register */
> > > > > - for (i = 0; i < 3; i++)
> > > > > - outb(preset >> (8 * i), base_offset);
> > > > > + spin_unlock(&priv->lock);
> > > > >
> > > > > return len;
> > > > > }
> > > > > @@ -1084,15 +1184,20 @@ static ssize_t quad8_count_preset_write(struct counter_device *counter,
> > > > > static ssize_t quad8_count_ceiling_read(struct counter_device *counter,
> > > > > struct counter_count *count, void *private, char *buf)
> > > > > {
> > > > > - const struct quad8_iio *const priv = counter->priv;
> > > > > + struct quad8_iio *const priv = counter->priv;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > >
> > > > > /* Range Limit and Modulo-N count modes use preset value as ceiling */
> > > > > switch (priv->count_mode[count->id]) {
> > > > > case 1:
> > > > > case 3:
> > > > > - return quad8_count_preset_read(counter, count, private, buf);
> > > > > + spin_unlock(&priv->lock);
> > > > > + return sprintf(buf, "%u\n", priv->preset[count->id]);
> > > > > }
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > /* By default 0x1FFFFFF (25 bits unsigned) is maximum count */
> > > > > return sprintf(buf, "33554431\n");
> > > > > }
> > > > > @@ -1101,15 +1206,29 @@ static ssize_t quad8_count_ceiling_write(struct counter_device *counter,
> > > > > struct counter_count *count, void *private, const char *buf, size_t len)
> > > > > {
> > > > > struct quad8_iio *const priv = counter->priv;
> > > > > + unsigned int ceiling;
> > > > > + int ret;
> > > > > +
> > > > > + ret = kstrtouint(buf, 0, &ceiling);
> > > > > + if (ret)
> > > > > + return ret;
> > > > > +
> > > > > + /* Only 24-bit values are supported */
> > > > > + if (ceiling > 0xFFFFFF)
> > > > > + return -EINVAL;
> > > > > +
> > > > > + spin_lock(&priv->lock);
> > > > >
> > > > > /* Range Limit and Modulo-N count modes use preset value as ceiling */
> > > > > switch (priv->count_mode[count->id]) {
> > > > > case 1:
> > > > > case 3:
> > > > > - return quad8_count_preset_write(counter, count, private, buf,
> > > > > - len);
> > > > > + quad8_preset_register_set(priv, count->id, ceiling);
> > > > > + break;
> > > > > }
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return len;
> > > > > }
> > > > >
> > > > > @@ -1137,6 +1256,8 @@ static ssize_t quad8_count_preset_enable_write(struct counter_device *counter,
> > > > > /* Preset enable is active low in Input/Output Control register */
> > > > > preset_enable = !preset_enable;
> > > > >
> > > > > + spin_lock(&priv->lock);
> > > > > +
> > > > > priv->preset_enable[count->id] = preset_enable;
> > > > >
> > > > > ior_cfg = priv->ab_enable[count->id] | (unsigned int)preset_enable << 1;
> > > > > @@ -1144,6 +1265,8 @@ static ssize_t quad8_count_preset_enable_write(struct counter_device *counter,
> > > > > /* Load I/O control configuration to Input / Output Control Register */
> > > > > outb(QUAD8_CTR_IOR | ior_cfg, base_offset);
> > > > >
> > > > > + spin_unlock(&priv->lock);
> > > > > +
> > > > > return len;
> > > > > }
> > > > >
> > > > > @@ -1429,6 +1552,9 @@ static int quad8_probe(struct device *dev, unsigned int id)
> > > > > quad8iio->counter.priv = quad8iio;
> > > > > quad8iio->base = base[id];
> > > > >
> > > > > + /* Initialize spin lock */
> > > > > + spin_lock_init(&quad8iio->lock);
> > > > > +
> > > > > /* Reset all counters and disable interrupt function */
> > > > > outb(QUAD8_CHAN_OP_RESET_COUNTERS, base[id] + QUAD8_REG_CHAN_OP);
> > > > > /* Set initial configuration for all counters */
> > > > > --
> > > > > 2.7.4
> > > > >
> > >
>

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