Re: [PATCH v2 9/9] gpio: pci-idio-16: make use of raw_spinlock variants

William Breathitt Gray
2017-03-22T12:55:13Z

On Tue, Mar 21, 2017 at 05:43:09PM -0500, Julia Cartwright wrote:
>The pci-idio-16 gpio driver 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>

Acked-by: William Breathitt Gray <vilhelm.gray@gmail.com>

>---
>New patch as of v2 of series.
>
> drivers/gpio/gpio-pci-idio-16.c | 28 ++++++++++++++--------------
> 1 file changed, 14 insertions(+), 14 deletions(-)
>
>diff --git a/drivers/gpio/gpio-pci-idio-16.c b/drivers/gpio/gpio-pci-idio-16.c
>index 269ab628634b..7de4f6a2cb49 100644
>--- a/drivers/gpio/gpio-pci-idio-16.c
>+++ b/drivers/gpio/gpio-pci-idio-16.c
>@@ -59,7 +59,7 @@ struct idio_16_gpio_reg {
> */
> struct idio_16_gpio {
> struct gpio_chip chip;
>- spinlock_t lock;
>+ raw_spinlock_t lock;
> struct idio_16_gpio_reg __iomem *reg;
> unsigned long irq_mask;
> };
>@@ -121,7 +121,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
> } else
> base = &idio16gpio->reg->out0_7;
>
>- spin_lock_irqsave(&idio16gpio->lock, flags);
>+ raw_spin_lock_irqsave(&idio16gpio->lock, flags);
>
> if (value)
> out_state = ioread8(base) | mask;
>@@ -130,7 +130,7 @@ static void idio_16_gpio_set(struct gpio_chip *chip, unsigned int offset,
>
> iowrite8(out_state, base);
>
>- spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+ raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
>
> static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
>@@ -140,7 +140,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
> unsigned long flags;
> unsigned int out_state;
>
>- spin_lock_irqsave(&idio16gpio->lock, flags);
>+ raw_spin_lock_irqsave(&idio16gpio->lock, flags);
>
> /* process output lines 0-7 */
> if (*mask & 0xFF) {
>@@ -160,7 +160,7 @@ static void idio_16_gpio_set_multiple(struct gpio_chip *chip,
> iowrite8(out_state, &idio16gpio->reg->out8_15);
> }
>
>- spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+ raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
>
> static void idio_16_irq_ack(struct irq_data *data)
>@@ -177,11 +177,11 @@ static void idio_16_irq_mask(struct irq_data *data)
> idio16gpio->irq_mask &= ~mask;
>
> if (!idio16gpio->irq_mask) {
>- spin_lock_irqsave(&idio16gpio->lock, flags);
>+ raw_spin_lock_irqsave(&idio16gpio->lock, flags);
>
> iowrite8(0, &idio16gpio->reg->irq_ctl);
>
>- spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+ raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
> }
>
>@@ -196,11 +196,11 @@ static void idio_16_irq_unmask(struct irq_data *data)
> idio16gpio->irq_mask |= mask;
>
> if (!prev_irq_mask) {
>- spin_lock_irqsave(&idio16gpio->lock, flags);
>+ raw_spin_lock_irqsave(&idio16gpio->lock, flags);
>
> ioread8(&idio16gpio->reg->irq_ctl);
>
>- spin_unlock_irqrestore(&idio16gpio->lock, flags);
>+ raw_spin_unlock_irqrestore(&idio16gpio->lock, flags);
> }
> }
>
>@@ -229,11 +229,11 @@ static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
> struct gpio_chip *const chip = &idio16gpio->chip;
> int gpio;
>
>- spin_lock(&idio16gpio->lock);
>+ raw_spin_lock(&idio16gpio->lock);
>
> irq_status = ioread8(&idio16gpio->reg->irq_status);
>
>- spin_unlock(&idio16gpio->lock);
>+ raw_spin_unlock(&idio16gpio->lock);
>
> /* Make sure our device generated IRQ */
> if (!(irq_status & 0x3) || !(irq_status & 0x4))
>@@ -242,12 +242,12 @@ static irqreturn_t idio_16_irq_handler(int irq, void *dev_id)
> for_each_set_bit(gpio, &idio16gpio->irq_mask, chip->ngpio)
> generic_handle_irq(irq_find_mapping(chip->irqdomain, gpio));
>
>- spin_lock(&idio16gpio->lock);
>+ raw_spin_lock(&idio16gpio->lock);
>
> /* Clear interrupt */
> iowrite8(0, &idio16gpio->reg->in0_7);
>
>- spin_unlock(&idio16gpio->lock);
>+ raw_spin_unlock(&idio16gpio->lock);
>
> return IRQ_HANDLED;
> }
>@@ -302,7 +302,7 @@ static int idio_16_probe(struct pci_dev *pdev, const struct pci_device_id *id)
> idio16gpio->chip.set = idio_16_gpio_set;
> idio16gpio->chip.set_multiple = idio_16_gpio_set_multiple;
>
>- spin_lock_init(&idio16gpio->lock);
>+ raw_spin_lock_init(&idio16gpio->lock);
>
> err = devm_gpiochip_add_data(dev, &idio16gpio->chip, idio16gpio);
> if (err) {
>--
>2.12.0
>