[PATCH 12/19] i2c: mux: pca954x: make use of raw_spinlock variants

From: Julia Cartwright
Date: Thu Mar 09 2017 - 12:06:23 EST


The pca954x i2c mux 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@xxxxxx>
---
drivers/i2c/muxes/i2c-mux-pca954x.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/drivers/i2c/muxes/i2c-mux-pca954x.c b/drivers/i2c/muxes/i2c-mux-pca954x.c
index dfc1c0e37c40..15dfc1648716 100644
--- a/drivers/i2c/muxes/i2c-mux-pca954x.c
+++ b/drivers/i2c/muxes/i2c-mux-pca954x.c
@@ -85,7 +85,7 @@ struct pca954x {

struct irq_domain *irq;
unsigned int irq_mask;
- spinlock_t lock;
+ raw_spinlock_t lock;
};

/* Provide specs for the PCA954x types we know about */
@@ -264,13 +264,13 @@ static void pca954x_irq_mask(struct irq_data *idata)
unsigned int pos = idata->hwirq;
unsigned long flags;

- spin_lock_irqsave(&data->lock, flags);
+ raw_spin_lock_irqsave(&data->lock, flags);

data->irq_mask &= ~BIT(pos);
if (!data->irq_mask)
disable_irq(data->client->irq);

- spin_unlock_irqrestore(&data->lock, flags);
+ raw_spin_unlock_irqrestore(&data->lock, flags);
}

static void pca954x_irq_unmask(struct irq_data *idata)
@@ -279,13 +279,13 @@ static void pca954x_irq_unmask(struct irq_data *idata)
unsigned int pos = idata->hwirq;
unsigned long flags;

- spin_lock_irqsave(&data->lock, flags);
+ raw_spin_lock_irqsave(&data->lock, flags);

if (!data->irq_mask)
enable_irq(data->client->irq);
data->irq_mask |= BIT(pos);

- spin_unlock_irqrestore(&data->lock, flags);
+ raw_spin_unlock_irqrestore(&data->lock, flags);
}

static int pca954x_irq_set_type(struct irq_data *idata, unsigned int type)
@@ -311,7 +311,7 @@ static int pca954x_irq_setup(struct i2c_mux_core *muxc)
if (!data->chip->has_irq || client->irq <= 0)
return 0;

- spin_lock_init(&data->lock);
+ raw_spin_lock_init(&data->lock);

data->irq = irq_domain_add_linear(client->dev.of_node,
data->chip->nchans,
--
2.11.1