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

From: William Breathitt Gray
Date: Fri Mar 13 2020 - 12:51:22 EST

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In reply to: Syed Nayyar Waris: "[PATCH v4 1/3] counter: 104-quad-8: Add lock guards - generic interface"
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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.

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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