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Date: Thu, 23 Mar 2017 13:42:57 +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 6/9] mfd: tc6393xb: make use of raw_spinlock variants
On Tue, 21 Mar 2017, Julia Cartwright wrote:
> The tc6393xb 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/tc6393xb.c | 52 +++++++++++++++++++++++++-------------------------
> 1 file changed, 26 insertions(+), 26 deletions(-)
Applied, thanks.
> diff --git a/drivers/mfd/tc6393xb.c b/drivers/mfd/tc6393xb.c
> index d42d322ac7ca..d16e71bd9482 100644
> --- a/drivers/mfd/tc6393xb.c
> +++ b/drivers/mfd/tc6393xb.c
> @@ -95,7 +95,7 @@ struct tc6393xb {
>
> struct clk *clk; /* 3,6 Mhz */
>
> - spinlock_t lock; /* protects RMW cycles */
> + raw_spinlock_t lock; /* protects RMW cycles */
>
> struct {
> u8 fer;
> @@ -126,13 +126,13 @@ static int tc6393xb_nand_enable(struct platform_device *nand)
> struct tc6393xb *tc6393xb = platform_get_drvdata(dev);
> unsigned long flags;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> /* SMD buffer on */
> dev_dbg(&dev->dev, "SMD buffer on\n");
> tmio_iowrite8(0xff, tc6393xb->scr + SCR_GPI_BCR(1));
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -226,7 +226,7 @@ static int tc6393xb_ohci_enable(struct platform_device *dev)
> u16 ccr;
> u8 fer;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> ccr = tmio_ioread16(tc6393xb->scr + SCR_CCR);
> ccr |= SCR_CCR_USBCK;
> @@ -236,7 +236,7 @@ static int tc6393xb_ohci_enable(struct platform_device *dev)
> fer |= SCR_FER_USBEN;
> tmio_iowrite8(fer, tc6393xb->scr + SCR_FER);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -248,7 +248,7 @@ static int tc6393xb_ohci_disable(struct platform_device *dev)
> u16 ccr;
> u8 fer;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> fer = tmio_ioread8(tc6393xb->scr + SCR_FER);
> fer &= ~SCR_FER_USBEN;
> @@ -258,7 +258,7 @@ static int tc6393xb_ohci_disable(struct platform_device *dev)
> ccr &= ~SCR_CCR_USBCK;
> tmio_iowrite16(ccr, tc6393xb->scr + SCR_CCR);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -280,14 +280,14 @@ static int tc6393xb_fb_enable(struct platform_device *dev)
> unsigned long flags;
> u16 ccr;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> ccr = tmio_ioread16(tc6393xb->scr + SCR_CCR);
> ccr &= ~SCR_CCR_MCLK_MASK;
> ccr |= SCR_CCR_MCLK_48;
> tmio_iowrite16(ccr, tc6393xb->scr + SCR_CCR);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -298,14 +298,14 @@ static int tc6393xb_fb_disable(struct platform_device *dev)
> unsigned long flags;
> u16 ccr;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> ccr = tmio_ioread16(tc6393xb->scr + SCR_CCR);
> ccr &= ~SCR_CCR_MCLK_MASK;
> ccr |= SCR_CCR_MCLK_OFF;
> tmio_iowrite16(ccr, tc6393xb->scr + SCR_CCR);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -317,7 +317,7 @@ int tc6393xb_lcd_set_power(struct platform_device *fb, bool on)
> u8 fer;
> unsigned long flags;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> fer = ioread8(tc6393xb->scr + SCR_FER);
> if (on)
> @@ -326,7 +326,7 @@ int tc6393xb_lcd_set_power(struct platform_device *fb, bool on)
> fer &= ~SCR_FER_SLCDEN;
> iowrite8(fer, tc6393xb->scr + SCR_FER);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -338,12 +338,12 @@ int tc6393xb_lcd_mode(struct platform_device *fb,
> struct tc6393xb *tc6393xb = platform_get_drvdata(dev);
> unsigned long flags;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> iowrite16(mode->pixclock, tc6393xb->scr + SCR_PLL1CR + 0);
> iowrite16(mode->pixclock >> 16, tc6393xb->scr + SCR_PLL1CR + 2);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -462,11 +462,11 @@ static void tc6393xb_gpio_set(struct gpio_chip *chip,
> struct tc6393xb *tc6393xb = gpiochip_get_data(chip);
> unsigned long flags;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> __tc6393xb_gpio_set(chip, offset, value);
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
> }
>
> static int tc6393xb_gpio_direction_input(struct gpio_chip *chip,
> @@ -476,13 +476,13 @@ static int tc6393xb_gpio_direction_input(struct gpio_chip *chip,
> unsigned long flags;
> u8 doecr;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> doecr = tmio_ioread8(tc6393xb->scr + SCR_GPO_DOECR(offset / 8));
> doecr &= ~TC_GPIO_BIT(offset);
> tmio_iowrite8(doecr, tc6393xb->scr + SCR_GPO_DOECR(offset / 8));
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -494,7 +494,7 @@ static int tc6393xb_gpio_direction_output(struct gpio_chip *chip,
> unsigned long flags;
> u8 doecr;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
>
> __tc6393xb_gpio_set(chip, offset, value);
>
> @@ -502,7 +502,7 @@ static int tc6393xb_gpio_direction_output(struct gpio_chip *chip,
> doecr |= TC_GPIO_BIT(offset);
> tmio_iowrite8(doecr, tc6393xb->scr + SCR_GPO_DOECR(offset / 8));
>
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
>
> return 0;
> }
> @@ -548,11 +548,11 @@ static void tc6393xb_irq_mask(struct irq_data *data)
> unsigned long flags;
> u8 imr;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
> imr = tmio_ioread8(tc6393xb->scr + SCR_IMR);
> imr |= 1 << (data->irq - tc6393xb->irq_base);
> tmio_iowrite8(imr, tc6393xb->scr + SCR_IMR);
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
> }
>
> static void tc6393xb_irq_unmask(struct irq_data *data)
> @@ -561,11 +561,11 @@ static void tc6393xb_irq_unmask(struct irq_data *data)
> unsigned long flags;
> u8 imr;
>
> - spin_lock_irqsave(&tc6393xb->lock, flags);
> + raw_spin_lock_irqsave(&tc6393xb->lock, flags);
> imr = tmio_ioread8(tc6393xb->scr + SCR_IMR);
> imr &= ~(1 << (data->irq - tc6393xb->irq_base));
> tmio_iowrite8(imr, tc6393xb->scr + SCR_IMR);
> - spin_unlock_irqrestore(&tc6393xb->lock, flags);
> + raw_spin_unlock_irqrestore(&tc6393xb->lock, flags);
> }
>
> static struct irq_chip tc6393xb_chip = {
> @@ -628,7 +628,7 @@ static int tc6393xb_probe(struct platform_device *dev)
> goto err_kzalloc;
> }
>
> - spin_lock_init(&tc6393xb->lock);
> + raw_spin_lock_init(&tc6393xb->lock);
>
> platform_set_drvdata(dev, tc6393xb);
>
--
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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