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Subject[PATCH v8 21/22] counter: 104-quad-8: Replace mutex with spinlock
Date
This patch replaces the mutex I/O lock with a spinlock. This is in
preparation for a subsequent patch adding IRQ support for 104-QUAD-8
devices; we can't sleep in an interrupt context, so we'll need to use a
spinlock instead.

Cc: Syed Nayyar Waris <syednwaris@gmail.com>
Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
---
drivers/counter/104-quad-8.c | 90 +++++++++++++++++++++---------------
1 file changed, 53 insertions(+), 37 deletions(-)

diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
index 41fdbd228be3..2b47f9991acc 100644
--- a/drivers/counter/104-quad-8.c
+++ b/drivers/counter/104-quad-8.c
@@ -16,6 +16,7 @@
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/types.h>
+#include <linux/spinlock.h>

#define QUAD8_EXTENT 32

@@ -28,6 +29,7 @@ MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");

/**
* struct quad8 - device private data structure
+ * @lock: synchronization lock to prevent I/O race conditions
* @counter: instance of the counter_device
* @fck_prescaler: array of filter clock prescaler configurations
* @preset: array of preset values
@@ -42,7 +44,7 @@ MODULE_PARM_DESC(base, "ACCES 104-QUAD-8 base addresses");
* @base: base port address of the device
*/
struct quad8 {
- struct mutex lock;
+ raw_spinlock_t lock;
struct counter_device counter;
unsigned int fck_prescaler[QUAD8_NUM_COUNTERS];
unsigned int preset[QUAD8_NUM_COUNTERS];
@@ -123,6 +125,7 @@ static int quad8_count_read(struct counter_device *counter,
unsigned int flags;
unsigned int borrow;
unsigned int carry;
+ unsigned long irqflags;
int i;

flags = inb(base_offset + 1);
@@ -132,7 +135,7 @@ static int quad8_count_read(struct counter_device *counter,
/* Borrow XOR Carry effectively doubles count range */
*val = (unsigned long)(borrow ^ carry) << 24;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

/* Reset Byte Pointer; transfer Counter to Output Latch */
outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_CNTR_OUT,
@@ -141,7 +144,7 @@ static int quad8_count_read(struct counter_device *counter,
for (i = 0; i < 3; i++)
*val |= (unsigned long)inb(base_offset) << (8 * i);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -151,13 +154,14 @@ static int quad8_count_write(struct counter_device *counter,
{
struct quad8 *const priv = counter->priv;
const int base_offset = priv->base + 2 * count->id;
+ unsigned long irqflags;
int i;

/* Only 24-bit values are supported */
if (val > 0xFFFFFF)
return -ERANGE;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

/* Reset Byte Pointer */
outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP, base_offset + 1);
@@ -182,7 +186,7 @@ static int quad8_count_write(struct counter_device *counter,
/* Reset Error flag */
outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_E, base_offset + 1);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -200,8 +204,9 @@ static int quad8_function_read(struct counter_device *counter,
{
struct quad8 *const priv = counter->priv;
const int id = count->id;
+ unsigned long irqflags;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

if (priv->quadrature_mode[id])
switch (priv->quadrature_scale[id]) {
@@ -218,7 +223,7 @@ static int quad8_function_read(struct counter_device *counter,
else
*function = COUNTER_FUNCTION_PULSE_DIRECTION;

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -233,10 +238,11 @@ static int quad8_function_write(struct counter_device *counter,
unsigned int *const scale = priv->quadrature_scale + id;
unsigned int *const synchronous_mode = priv->synchronous_mode + id;
const int base_offset = priv->base + 2 * id + 1;
+ unsigned long irqflags;
unsigned int mode_cfg;
unsigned int idr_cfg;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

mode_cfg = priv->count_mode[id] << 1;
idr_cfg = priv->index_polarity[id] << 1;
@@ -271,7 +277,7 @@ static int quad8_function_write(struct counter_device *counter,
break;
default:
/* should never reach this path */
- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);
return -EINVAL;
}
}
@@ -279,7 +285,7 @@ static int quad8_function_write(struct counter_device *counter,
/* Load mode configuration to Counter Mode Register */
outb(QUAD8_CTR_CMR | mode_cfg, base_offset);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -407,9 +413,10 @@ static int quad8_index_polarity_set(struct counter_device *counter,
struct quad8 *const priv = counter->priv;
const size_t channel_id = signal->id - 16;
const int base_offset = priv->base + 2 * channel_id + 1;
+ unsigned long irqflags;
unsigned int idr_cfg = index_polarity << 1;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

idr_cfg |= priv->synchronous_mode[channel_id];

@@ -418,7 +425,7 @@ static int quad8_index_polarity_set(struct counter_device *counter,
/* Load Index Control configuration to Index Control Register */
outb(QUAD8_CTR_IDR | idr_cfg, base_offset);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -447,15 +454,16 @@ static int quad8_synchronous_mode_set(struct counter_device *counter,
struct quad8 *const priv = counter->priv;
const size_t channel_id = signal->id - 16;
const int base_offset = priv->base + 2 * channel_id + 1;
+ unsigned long irqflags;
unsigned int idr_cfg = synchronous_mode;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

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]) {
- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);
return -EINVAL;
}

@@ -464,7 +472,7 @@ static int quad8_synchronous_mode_set(struct counter_device *counter,
/* Load Index Control configuration to Index Control Register */
outb(QUAD8_CTR_IDR | idr_cfg, base_offset);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -511,6 +519,7 @@ static int quad8_count_mode_write(struct counter_device *counter,
unsigned int count_mode;
unsigned int mode_cfg;
const int base_offset = priv->base + 2 * count->id + 1;
+ unsigned long irqflags;

/* Map Generic Counter count mode to 104-QUAD-8 count mode */
switch (cnt_mode) {
@@ -531,7 +540,7 @@ static int quad8_count_mode_write(struct counter_device *counter,
return -EINVAL;
}

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

priv->count_mode[count->id] = count_mode;

@@ -545,7 +554,7 @@ static int quad8_count_mode_write(struct counter_device *counter,
/* Load mode configuration to Counter Mode Register */
outb(QUAD8_CTR_CMR | mode_cfg, base_offset);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -565,9 +574,10 @@ static int quad8_count_enable_write(struct counter_device *counter,
{
struct quad8 *const priv = counter->priv;
const int base_offset = priv->base + 2 * count->id;
+ unsigned long irqflags;
unsigned int ior_cfg;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

priv->ab_enable[count->id] = enable;

@@ -576,7 +586,7 @@ static int quad8_count_enable_write(struct counter_device *counter,
/* Load I/O control configuration */
outb(QUAD8_CTR_IOR | ior_cfg, base_offset + 1);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -627,16 +637,17 @@ static int quad8_count_preset_write(struct counter_device *counter,
struct counter_count *count, u64 preset)
{
struct quad8 *const priv = counter->priv;
+ unsigned long irqflags;

/* Only 24-bit values are supported */
if (preset > 0xFFFFFF)
return -ERANGE;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

quad8_preset_register_set(priv, count->id, preset);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -645,8 +656,9 @@ static int quad8_count_ceiling_read(struct counter_device *counter,
struct counter_count *count, u64 *ceiling)
{
struct quad8 *const priv = counter->priv;
+ unsigned long irqflags;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

/* Range Limit and Modulo-N count modes use preset value as ceiling */
switch (priv->count_mode[count->id]) {
@@ -660,7 +672,7 @@ static int quad8_count_ceiling_read(struct counter_device *counter,
break;
}

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -669,23 +681,24 @@ static int quad8_count_ceiling_write(struct counter_device *counter,
struct counter_count *count, u64 ceiling)
{
struct quad8 *const priv = counter->priv;
+ unsigned long irqflags;

/* Only 24-bit values are supported */
if (ceiling > 0xFFFFFF)
return -ERANGE;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

/* Range Limit and Modulo-N count modes use preset value as ceiling */
switch (priv->count_mode[count->id]) {
case 1:
case 3:
- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);
quad8_preset_register_set(priv, count->id, ceiling);
return 0;
}

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return -EINVAL;
}
@@ -707,12 +720,13 @@ static int quad8_count_preset_enable_write(struct counter_device *counter,
{
struct quad8 *const priv = counter->priv;
const int base_offset = priv->base + 2 * count->id + 1;
+ unsigned long irqflags;
unsigned int ior_cfg;

/* Preset enable is active low in Input/Output Control register */
preset_enable = !preset_enable;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

priv->preset_enable[count->id] = preset_enable;

@@ -721,7 +735,7 @@ static int 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);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -732,22 +746,23 @@ static int quad8_signal_cable_fault_read(struct counter_device *counter,
{
struct quad8 *const priv = counter->priv;
const size_t channel_id = signal->id / 2;
+ unsigned long irqflags;
bool disabled;
unsigned int status;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

disabled = !(priv->cable_fault_enable & BIT(channel_id));

if (disabled) {
- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);
return -EINVAL;
}

/* Logic 0 = cable fault */
status = inb(priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

/* Mask respective channel and invert logic */
*cable_fault = !(status & BIT(channel_id));
@@ -773,9 +788,10 @@ static int quad8_signal_cable_fault_enable_write(struct counter_device *counter,
{
struct quad8 *const priv = counter->priv;
const size_t channel_id = signal->id / 2;
+ unsigned long irqflags;
unsigned int cable_fault_enable;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

if (enable)
priv->cable_fault_enable |= BIT(channel_id);
@@ -787,7 +803,7 @@ static int quad8_signal_cable_fault_enable_write(struct counter_device *counter,

outb(cable_fault_enable, priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -810,8 +826,9 @@ static int quad8_signal_fck_prescaler_write(struct counter_device *counter,
struct quad8 *const priv = counter->priv;
const size_t channel_id = signal->id / 2;
const int base_offset = priv->base + 2 * channel_id;
+ unsigned long irqflags;

- mutex_lock(&priv->lock);
+ raw_spin_lock_irqsave(&priv->lock, irqflags);

priv->fck_prescaler[channel_id] = prescaler;

@@ -823,7 +840,7 @@ static int quad8_signal_fck_prescaler_write(struct counter_device *counter,
outb(QUAD8_CTR_RLD | QUAD8_RLD_RESET_BP | QUAD8_RLD_PRESET_PSC,
base_offset + 1);

- mutex_unlock(&priv->lock);
+ raw_spin_unlock_irqrestore(&priv->lock, irqflags);

return 0;
}
@@ -992,8 +1009,7 @@ static int quad8_probe(struct device *dev, unsigned int id)
priv->counter.priv = priv;
priv->base = base[id];

- /* Initialize mutex */
- mutex_init(&priv->lock);
+ raw_spin_lock_init(&priv->lock);

/* Reset all counters and disable interrupt function */
outb(QUAD8_CHAN_OP_RESET_COUNTERS, base[id] + QUAD8_REG_CHAN_OP);
--
2.30.0
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