linux-kernel - Re: [PATCH v2 5/9] mfd: t7l66xb: make use of raw

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Date:   Thu, 23 Mar 2017 13:42:47 +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 5/9] mfd: t7l66xb: make use of raw_spinlock variants

On Tue, 21 Mar 2017, Julia Cartwright wrote:

> The t7l66xb 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/t7l66xb.c | 20 ++++++++++----------
>  1 file changed, 10 insertions(+), 10 deletions(-)

Applied, thanks.

> diff --git a/drivers/mfd/t7l66xb.c b/drivers/mfd/t7l66xb.c
> index 94bd89cb1f06..22c811396edc 100644
> --- a/drivers/mfd/t7l66xb.c
> +++ b/drivers/mfd/t7l66xb.c
> @@ -69,7 +69,7 @@ static const struct resource t7l66xb_mmc_resources[] = {
>  struct t7l66xb {
>  	void __iomem		*scr;
>  	/* Lock to protect registers requiring read/modify/write ops. */
> -	spinlock_t		lock;
> +	raw_spinlock_t		lock;
>  
>  	struct resource		rscr;
>  	struct clk		*clk48m;
> @@ -89,13 +89,13 @@ static int t7l66xb_mmc_enable(struct platform_device *mmc)
>  
>  	clk_prepare_enable(t7l66xb->clk32k);
>  
> -	spin_lock_irqsave(&t7l66xb->lock, flags);
> +	raw_spin_lock_irqsave(&t7l66xb->lock, flags);
>  
>  	dev_ctl = tmio_ioread8(t7l66xb->scr + SCR_DEV_CTL);
>  	dev_ctl |= SCR_DEV_CTL_MMC;
>  	tmio_iowrite8(dev_ctl, t7l66xb->scr + SCR_DEV_CTL);
>  
> -	spin_unlock_irqrestore(&t7l66xb->lock, flags);
> +	raw_spin_unlock_irqrestore(&t7l66xb->lock, flags);
>  
>  	tmio_core_mmc_enable(t7l66xb->scr + 0x200, 0,
>  		t7l66xb_mmc_resources[0].start & 0xfffe);
> @@ -110,13 +110,13 @@ static int t7l66xb_mmc_disable(struct platform_device *mmc)
>  	unsigned long flags;
>  	u8 dev_ctl;
>  
> -	spin_lock_irqsave(&t7l66xb->lock, flags);
> +	raw_spin_lock_irqsave(&t7l66xb->lock, flags);
>  
>  	dev_ctl = tmio_ioread8(t7l66xb->scr + SCR_DEV_CTL);
>  	dev_ctl &= ~SCR_DEV_CTL_MMC;
>  	tmio_iowrite8(dev_ctl, t7l66xb->scr + SCR_DEV_CTL);
>  
> -	spin_unlock_irqrestore(&t7l66xb->lock, flags);
> +	raw_spin_unlock_irqrestore(&t7l66xb->lock, flags);
>  
>  	clk_disable_unprepare(t7l66xb->clk32k);
>  
> @@ -206,11 +206,11 @@ static void t7l66xb_irq_mask(struct irq_data *data)
>  	unsigned long			flags;
>  	u8 imr;
>  
> -	spin_lock_irqsave(&t7l66xb->lock, flags);
> +	raw_spin_lock_irqsave(&t7l66xb->lock, flags);
>  	imr = tmio_ioread8(t7l66xb->scr + SCR_IMR);
>  	imr |= 1 << (data->irq - t7l66xb->irq_base);
>  	tmio_iowrite8(imr, t7l66xb->scr + SCR_IMR);
> -	spin_unlock_irqrestore(&t7l66xb->lock, flags);
> +	raw_spin_unlock_irqrestore(&t7l66xb->lock, flags);
>  }
>  
>  static void t7l66xb_irq_unmask(struct irq_data *data)
> @@ -219,11 +219,11 @@ static void t7l66xb_irq_unmask(struct irq_data *data)
>  	unsigned long flags;
>  	u8 imr;
>  
> -	spin_lock_irqsave(&t7l66xb->lock, flags);
> +	raw_spin_lock_irqsave(&t7l66xb->lock, flags);
>  	imr = tmio_ioread8(t7l66xb->scr + SCR_IMR);
>  	imr &= ~(1 << (data->irq - t7l66xb->irq_base));
>  	tmio_iowrite8(imr, t7l66xb->scr + SCR_IMR);
> -	spin_unlock_irqrestore(&t7l66xb->lock, flags);
> +	raw_spin_unlock_irqrestore(&t7l66xb->lock, flags);
>  }
>  
>  static struct irq_chip t7l66xb_chip = {
> @@ -321,7 +321,7 @@ static int t7l66xb_probe(struct platform_device *dev)
>  	if (!t7l66xb)
>  		return -ENOMEM;
>  
> -	spin_lock_init(&t7l66xb->lock);
> +	raw_spin_lock_init(&t7l66xb->lock);
>  
>  	platform_set_drvdata(dev, t7l66xb);
>  

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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