[PATCH v2 3/9] powerpc: mpc52xx_gpt: make use of raw_spinlock variants

Julia Cartwright
2017-03-21T22:43:03Z

The mpc52xx_gpt code currently implements an irq_chip for handling
interrupts; due to how irq_chip handling is done, it's necessary for the
irq_chip methods to be invoked from hardirq context, even on a a
real-time kernel. Because the spinlock_t type becomes a "sleeping"
spinlock w/ RT kernels, it is not suitable to be used with irq_chips.

A quick audit of the operations under the lock reveal that they do only
minimal, bounded work, and are therefore safe to do under a raw spinlock.

Signed-off-by: Julia Cartwright <julia@ni.com>
---
v1 -> v2:
- No change.

arch/powerpc/platforms/52xx/mpc52xx_gpt.c | 52 +++++++++++++++----------------
1 file changed, 26 insertions(+), 26 deletions(-)

diff --git a/arch/powerpc/platforms/52xx/mpc52xx_gpt.c b/arch/powerpc/platforms/52xx/mpc52xx_gpt.c
index 22645a7c6b8a..18c1383717f2 100644
--- a/arch/powerpc/platforms/52xx/mpc52xx_gpt.c
+++ b/arch/powerpc/platforms/52xx/mpc52xx_gpt.c
@@ -90,7 +90,7 @@ struct mpc52xx_gpt_priv {
struct list_head list; /* List of all GPT devices */
struct device *dev;
struct mpc52xx_gpt __iomem *regs;
- spinlock_t lock;
+ raw_spinlock_t lock;
struct irq_domain *irqhost;
u32 ipb_freq;
u8 wdt_mode;
@@ -141,9 +141,9 @@ static void mpc52xx_gpt_irq_unmask(struct irq_data *d)
struct mpc52xx_gpt_priv *gpt = irq_data_get_irq_chip_data(d);
unsigned long flags;

- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
setbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_IRQ_EN);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);
}

static void mpc52xx_gpt_irq_mask(struct irq_data *d)
@@ -151,9 +151,9 @@ static void mpc52xx_gpt_irq_mask(struct irq_data *d)
struct mpc52xx_gpt_priv *gpt = irq_data_get_irq_chip_data(d);
unsigned long flags;

- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
clrbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_IRQ_EN);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);
}

static void mpc52xx_gpt_irq_ack(struct irq_data *d)
@@ -171,14 +171,14 @@ static int mpc52xx_gpt_irq_set_type(struct irq_data *d, unsigned int flow_type)

dev_dbg(gpt->dev, "%s: virq=%i type=%x\n", __func__, d->irq, flow_type);

- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
reg = in_be32(&gpt->regs->mode) & ~MPC52xx_GPT_MODE_ICT_MASK;
if (flow_type & IRQF_TRIGGER_RISING)
reg |= MPC52xx_GPT_MODE_ICT_RISING;
if (flow_type & IRQF_TRIGGER_FALLING)
reg |= MPC52xx_GPT_MODE_ICT_FALLING;
out_be32(&gpt->regs->mode, reg);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);

return 0;
}
@@ -264,11 +264,11 @@ mpc52xx_gpt_irq_setup(struct mpc52xx_gpt_priv *gpt, struct device_node *node)
/* If the GPT is currently disabled, then change it to be in Input
* Capture mode. If the mode is non-zero, then the pin could be
* already in use for something. */
- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
mode = in_be32(&gpt->regs->mode);
if ((mode & MPC52xx_GPT_MODE_MS_MASK) == 0)
out_be32(&gpt->regs->mode, mode | MPC52xx_GPT_MODE_MS_IC);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);

dev_dbg(gpt->dev, "%s() complete. virq=%i\n", __func__, cascade_virq);
}
@@ -295,9 +295,9 @@ mpc52xx_gpt_gpio_set(struct gpio_chip *gc, unsigned int gpio, int v)
dev_dbg(gpt->dev, "%s: gpio:%d v:%d\n", __func__, gpio, v);
r = v ? MPC52xx_GPT_MODE_GPIO_OUT_HIGH : MPC52xx_GPT_MODE_GPIO_OUT_LOW;

- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
clrsetbits_be32(&gpt->regs->mode, MPC52xx_GPT_MODE_GPIO_MASK, r);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);
}

static int mpc52xx_gpt_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)
@@ -307,9 +307,9 @@ static int mpc52xx_gpt_gpio_dir_in(struct gpio_chip *gc, unsigned int gpio)

dev_dbg(gpt->dev, "%s: gpio:%d\n", __func__, gpio);

- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
clrbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_GPIO_MASK);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);

return 0;
}
@@ -436,16 +436,16 @@ static int mpc52xx_gpt_do_start(struct mpc52xx_gpt_priv *gpt, u64 period,
}

/* Set and enable the timer, reject an attempt to use a wdt as gpt */
- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
if (as_wdt)
gpt->wdt_mode |= MPC52xx_GPT_IS_WDT;
else if ((gpt->wdt_mode & MPC52xx_GPT_IS_WDT) != 0) {
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);
return -EBUSY;
}
out_be32(&gpt->regs->count, prescale << 16 | clocks);
clrsetbits_be32(&gpt->regs->mode, clear, set);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);

return 0;
}
@@ -476,14 +476,14 @@ int mpc52xx_gpt_stop_timer(struct mpc52xx_gpt_priv *gpt)
unsigned long flags;

/* reject the operation if the timer is used as watchdog (gpt 0 only) */
- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
if ((gpt->wdt_mode & MPC52xx_GPT_IS_WDT) != 0) {
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);
return -EBUSY;
}

clrbits32(&gpt->regs->mode, MPC52xx_GPT_MODE_COUNTER_ENABLE);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);
return 0;
}
EXPORT_SYMBOL(mpc52xx_gpt_stop_timer);
@@ -500,9 +500,9 @@ u64 mpc52xx_gpt_timer_period(struct mpc52xx_gpt_priv *gpt)
u64 prescale;
unsigned long flags;

- spin_lock_irqsave(&gpt->lock, flags);
+ raw_spin_lock_irqsave(&gpt->lock, flags);
period = in_be32(&gpt->regs->count);
- spin_unlock_irqrestore(&gpt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt->lock, flags);

prescale = period >> 16;
period &= 0xffff;
@@ -532,9 +532,9 @@ static inline void mpc52xx_gpt_wdt_ping(struct mpc52xx_gpt_priv *gpt_wdt)
{
unsigned long flags;

- spin_lock_irqsave(&gpt_wdt->lock, flags);
+ raw_spin_lock_irqsave(&gpt_wdt->lock, flags);
out_8((u8 *) &gpt_wdt->regs->mode, MPC52xx_GPT_MODE_WDT_PING);
- spin_unlock_irqrestore(&gpt_wdt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt_wdt->lock, flags);
}

/* wdt misc device api */
@@ -638,11 +638,11 @@ static int mpc52xx_wdt_release(struct inode *inode, struct file *file)
struct mpc52xx_gpt_priv *gpt_wdt = file->private_data;
unsigned long flags;

- spin_lock_irqsave(&gpt_wdt->lock, flags);
+ raw_spin_lock_irqsave(&gpt_wdt->lock, flags);
clrbits32(&gpt_wdt->regs->mode,
MPC52xx_GPT_MODE_COUNTER_ENABLE | MPC52xx_GPT_MODE_WDT_EN);
gpt_wdt->wdt_mode &= ~MPC52xx_GPT_IS_WDT;
- spin_unlock_irqrestore(&gpt_wdt->lock, flags);
+ raw_spin_unlock_irqrestore(&gpt_wdt->lock, flags);
#endif
clear_bit(0, &wdt_is_active);
return 0;
@@ -723,7 +723,7 @@ static int mpc52xx_gpt_probe(struct platform_device *ofdev)
if (!gpt)
return -ENOMEM;

- spin_lock_init(&gpt->lock);
+ raw_spin_lock_init(&gpt->lock);
gpt->dev = &ofdev->dev;
gpt->ipb_freq = mpc5xxx_get_bus_frequency(ofdev->dev.of_node);
gpt->regs = of_iomap(ofdev->dev.of_node, 0);
--
2.12.0