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    Subject[PATCH 12/19] i2c: mux: pca954x: make use of raw_spinlock variants
    Date
    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@ni.com>
    ---
    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
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