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Date: Thu, 23 Mar 2017 13:42:36 +0000
From: Lee Jones <lee.jones@...aro.org>
To: Julia Cartwright <julia@...com>
Cc: linux-kernel@...r.kernel.org, linux-rt-users@...r.kernel.org
Subject: Re: [PATCH v2 4/9] mfd: asic3: make use of raw_spinlock variants
On Tue, 21 Mar 2017, Julia Cartwright wrote:
> The asic3 mfd 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.
>
> Acked-for-MFD-by: Lee Jones <lee.jones@...aro.org>
> Signed-off-by: Julia Cartwright <julia@...com>
> ---
> v1 -> v2:
> - No functional change. Added Lee's ack.
>
> drivers/mfd/asic3.c | 56 ++++++++++++++++++++++++++---------------------------
> 1 file changed, 28 insertions(+), 28 deletions(-)
Applied, thanks.
> diff --git a/drivers/mfd/asic3.c b/drivers/mfd/asic3.c
> index 0413c8159551..cf2e25ab2940 100644
> --- a/drivers/mfd/asic3.c
> +++ b/drivers/mfd/asic3.c
> @@ -78,7 +78,7 @@ struct asic3 {
> unsigned int bus_shift;
> unsigned int irq_nr;
> unsigned int irq_base;
> - spinlock_t lock;
> + raw_spinlock_t lock;
> u16 irq_bothedge[4];
> struct gpio_chip gpio;
> struct device *dev;
> @@ -108,14 +108,14 @@ static void asic3_set_register(struct asic3 *asic, u32 reg, u32 bits, bool set)
> unsigned long flags;
> u32 val;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> val = asic3_read_register(asic, reg);
> if (set)
> val |= bits;
> else
> val &= ~bits;
> asic3_write_register(asic, reg, val);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> /* IRQs */
> @@ -129,13 +129,13 @@ static void asic3_irq_flip_edge(struct asic3 *asic,
> u16 edge;
> unsigned long flags;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> edge = asic3_read_register(asic,
> base + ASIC3_GPIO_EDGE_TRIGGER);
> edge ^= bit;
> asic3_write_register(asic,
> base + ASIC3_GPIO_EDGE_TRIGGER, edge);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static void asic3_irq_demux(struct irq_desc *desc)
> @@ -151,10 +151,10 @@ static void asic3_irq_demux(struct irq_desc *desc)
> u32 status;
> int bank;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> status = asic3_read_register(asic,
> ASIC3_OFFSET(INTR, P_INT_STAT));
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
>
> /* Check all ten register bits */
> if ((status & 0x3ff) == 0)
> @@ -167,7 +167,7 @@ static void asic3_irq_demux(struct irq_desc *desc)
>
> base = ASIC3_GPIO_A_BASE
> + bank * ASIC3_GPIO_BASE_INCR;
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> istat = asic3_read_register(asic,
> base +
> ASIC3_GPIO_INT_STATUS);
> @@ -175,7 +175,7 @@ static void asic3_irq_demux(struct irq_desc *desc)
> asic3_write_register(asic,
> base +
> ASIC3_GPIO_INT_STATUS, 0);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
>
> for (i = 0; i < ASIC3_GPIOS_PER_BANK; i++) {
> int bit = (1 << i);
> @@ -230,11 +230,11 @@ static void asic3_mask_gpio_irq(struct irq_data *data)
> bank = asic3_irq_to_bank(asic, data->irq);
> index = asic3_irq_to_index(asic, data->irq);
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> val = asic3_read_register(asic, bank + ASIC3_GPIO_MASK);
> val |= 1 << index;
> asic3_write_register(asic, bank + ASIC3_GPIO_MASK, val);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static void asic3_mask_irq(struct irq_data *data)
> @@ -243,7 +243,7 @@ static void asic3_mask_irq(struct irq_data *data)
> int regval;
> unsigned long flags;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> regval = asic3_read_register(asic,
> ASIC3_INTR_BASE +
> ASIC3_INTR_INT_MASK);
> @@ -255,7 +255,7 @@ static void asic3_mask_irq(struct irq_data *data)
> ASIC3_INTR_BASE +
> ASIC3_INTR_INT_MASK,
> regval);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static void asic3_unmask_gpio_irq(struct irq_data *data)
> @@ -267,11 +267,11 @@ static void asic3_unmask_gpio_irq(struct irq_data *data)
> bank = asic3_irq_to_bank(asic, data->irq);
> index = asic3_irq_to_index(asic, data->irq);
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> val = asic3_read_register(asic, bank + ASIC3_GPIO_MASK);
> val &= ~(1 << index);
> asic3_write_register(asic, bank + ASIC3_GPIO_MASK, val);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static void asic3_unmask_irq(struct irq_data *data)
> @@ -280,7 +280,7 @@ static void asic3_unmask_irq(struct irq_data *data)
> int regval;
> unsigned long flags;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> regval = asic3_read_register(asic,
> ASIC3_INTR_BASE +
> ASIC3_INTR_INT_MASK);
> @@ -292,7 +292,7 @@ static void asic3_unmask_irq(struct irq_data *data)
> ASIC3_INTR_BASE +
> ASIC3_INTR_INT_MASK,
> regval);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static int asic3_gpio_irq_type(struct irq_data *data, unsigned int type)
> @@ -306,7 +306,7 @@ static int asic3_gpio_irq_type(struct irq_data *data, unsigned int type)
> index = asic3_irq_to_index(asic, data->irq);
> bit = 1<<index;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> level = asic3_read_register(asic,
> bank + ASIC3_GPIO_LEVEL_TRIGGER);
> edge = asic3_read_register(asic,
> @@ -348,7 +348,7 @@ static int asic3_gpio_irq_type(struct irq_data *data, unsigned int type)
> edge);
> asic3_write_register(asic, bank + ASIC3_GPIO_TRIGGER_TYPE,
> trigger);
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> return 0;
> }
>
> @@ -455,7 +455,7 @@ static int asic3_gpio_direction(struct gpio_chip *chip,
> return -EINVAL;
> }
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
>
> out_reg = asic3_read_register(asic, gpio_base + ASIC3_GPIO_DIRECTION);
>
> @@ -467,7 +467,7 @@ static int asic3_gpio_direction(struct gpio_chip *chip,
>
> asic3_write_register(asic, gpio_base + ASIC3_GPIO_DIRECTION, out_reg);
>
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
>
> return 0;
>
> @@ -524,7 +524,7 @@ static void asic3_gpio_set(struct gpio_chip *chip,
>
> mask = ASIC3_GPIO_TO_MASK(offset);
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
>
> out_reg = asic3_read_register(asic, gpio_base + ASIC3_GPIO_OUT);
>
> @@ -535,7 +535,7 @@ static void asic3_gpio_set(struct gpio_chip *chip,
>
> asic3_write_register(asic, gpio_base + ASIC3_GPIO_OUT, out_reg);
>
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static int asic3_gpio_to_irq(struct gpio_chip *chip, unsigned offset)
> @@ -611,13 +611,13 @@ static void asic3_clk_enable(struct asic3 *asic, struct asic3_clk *clk)
> unsigned long flags;
> u32 cdex;
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> if (clk->enabled++ == 0) {
> cdex = asic3_read_register(asic, ASIC3_OFFSET(CLOCK, CDEX));
> cdex |= clk->cdex;
> asic3_write_register(asic, ASIC3_OFFSET(CLOCK, CDEX), cdex);
> }
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> static void asic3_clk_disable(struct asic3 *asic, struct asic3_clk *clk)
> @@ -627,13 +627,13 @@ static void asic3_clk_disable(struct asic3 *asic, struct asic3_clk *clk)
>
> WARN_ON(clk->enabled == 0);
>
> - spin_lock_irqsave(&asic->lock, flags);
> + raw_spin_lock_irqsave(&asic->lock, flags);
> if (--clk->enabled == 0) {
> cdex = asic3_read_register(asic, ASIC3_OFFSET(CLOCK, CDEX));
> cdex &= ~clk->cdex;
> asic3_write_register(asic, ASIC3_OFFSET(CLOCK, CDEX), cdex);
> }
> - spin_unlock_irqrestore(&asic->lock, flags);
> + raw_spin_unlock_irqrestore(&asic->lock, flags);
> }
>
> /* MFD cells (SPI, PWM, LED, DS1WM, MMC) */
> @@ -963,7 +963,7 @@ static int __init asic3_probe(struct platform_device *pdev)
> if (!asic)
> return -ENOMEM;
>
> - spin_lock_init(&asic->lock);
> + raw_spin_lock_init(&asic->lock);
> platform_set_drvdata(pdev, asic);
> asic->dev = &pdev->dev;
>
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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