[PATCH] drivers/spi/atmel_spi.c: prevent premature irqs

[PATCH] drivers/spi/atmel_spi.c: prevent premature irqs

[Voss, Nikolaus]

When restarting a kernel using kexec, filled rx buffers on SPI master
interface reliably crash the kernel. This patch disables rx interrupts
on startup to avoid this. Interrupts will be regulary enabled at start
of a new SPI master transfer.

Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
---
 drivers/spi/atmel_spi.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
index 1a478bf..d17f14c 100644
--- a/drivers/spi/atmel_spi.c
+++ b/drivers/spi/atmel_spi.c
@@ -811,6 +811,9 @@ static int __init atmel_spi_probe(struct platform_device *pdev)
 	as->irq = irq;
 	as->clk = clk;
 
+	/* disable rx interrupts to avoid premature irq triggering */
+	spi_writel(as, IDR, SPI_BIT(RXBUFF) | SPI_BIT(ENDRX) | SPI_BIT(OVRES));
+
 	ret = request_irq(irq, atmel_spi_interrupt, 0,
 			dev_name(&pdev->dev), master);
 	if (ret)
-- 
1.5.4.3

Re: [PATCH] drivers/spi/atmel_spi.c: prevent premature irqs

[Nicolas Ferre]

Le 11/04/2011 08:53, Voss, Nikolaus :
> When restarting a kernel using kexec, filled rx buffers on SPI master
> interface reliably crash the kernel. This patch disables rx interrupts
> on startup to avoid this. Interrupts will be regulary enabled at start
> of a new SPI master transfer.
> 
> Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>
> ---
>  drivers/spi/atmel_spi.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
> index 1a478bf..d17f14c 100644
> --- a/drivers/spi/atmel_spi.c
> +++ b/drivers/spi/atmel_spi.c
> @@ -811,6 +811,9 @@ static int __init atmel_spi_probe(struct platform_device *pdev)
>  	as->irq = irq;
>  	as->clk = clk;
>  
> +	/* disable rx interrupts to avoid premature irq triggering */
> +	spi_writel(as, IDR, SPI_BIT(RXBUFF) | SPI_BIT(ENDRX) | SPI_BIT(OVRES));
> +

What about something like this?

/* disable all interrupts to avoid premature irq triggering */
spi_writel(as, IDR, 0xffffffff);


>  	ret = request_irq(irq, atmel_spi_interrupt, 0,
>  			dev_name(&pdev->dev), master);
>  	if (ret)

Best regards,
-- 
Nicolas Ferre

RE: [PATCH] drivers/spi/atmel_spi.c: prevent premature irqs

[Voss, Nikolaus]

Hi,

> What about something like this?
> 
> /* disable all interrupts to avoid premature irq triggering */
> spi_writel(as, IDR, 0xffffffff);

I implemented it this way the first time, but on a second approach I used
the more specific variant.

That way it is kept symmetric to the irq enable part in the transfer method
which enables no more than the irqs disabled in my patch. And I generally
feel better when not writing live values to don't care bits ;-).

It's a matter of taste after all.

Best regards,
Nikolaus Voss

Re: [PATCH] drivers/spi/atmel_spi.c: prevent premature irqs

[Nicolas Ferre]

Le 11/04/2011 11:38, Voss, Nikolaus :
> Hi,
> 
>> What about something like this?
>>
>> /* disable all interrupts to avoid premature irq triggering */
>> spi_writel(as, IDR, 0xffffffff);
> 
> I implemented it this way the first time, but on a second approach I used
> the more specific variant.
> 
> That way it is kept symmetric to the irq enable part in the transfer method
> which enables no more than the irqs disabled in my patch. And I generally
> feel better when not writing live values to don't care bits ;-).

That makes sense. I add my ACK.

Bye,
-- 
Nicolas Ferre

Re: [PATCH] drivers/spi/atmel_spi.c: prevent premature irqs

[Nicolas Ferre]

Le 11/04/2011 08:53, Voss, Nikolaus :
> When restarting a kernel using kexec, filled rx buffers on SPI master
> interface reliably crash the kernel. This patch disables rx interrupts
> on startup to avoid this. Interrupts will be regulary enabled at start
> of a new SPI master transfer.
> 
> Signed-off-by: Nikolaus Voss <n.voss@weinmann.de>

Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>

> ---
>  drivers/spi/atmel_spi.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/spi/atmel_spi.c b/drivers/spi/atmel_spi.c
> index 1a478bf..d17f14c 100644
> --- a/drivers/spi/atmel_spi.c
> +++ b/drivers/spi/atmel_spi.c
> @@ -811,6 +811,9 @@ static int __init atmel_spi_probe(struct platform_device *pdev)
>  	as->irq = irq;
>  	as->clk = clk;
>  
> +	/* disable rx interrupts to avoid premature irq triggering */
> +	spi_writel(as, IDR, SPI_BIT(RXBUFF) | SPI_BIT(ENDRX) | SPI_BIT(OVRES));
> +
>  	ret = request_irq(irq, atmel_spi_interrupt, 0,
>  			dev_name(&pdev->dev), master);
>  	if (ret)


-- 
Nicolas Ferre