Re: GPIO level IRQ fires twice each time.

[Kent Gibson <warthog618@gmail.com>]

On Fri, Jan 21, 2022 at 09:03:43AM +0000, Markus Mirevik wrote:
> I have a problem with a custom bord based on SoC am335x and a driver utilizing a GPIO line for interrupts. 
> 
> I have two mcp2518fd chip connected on one SPI line and everything works, but it's hogs a lot of CPU.
> In the current setup only one chip is connected and it only receives packets.
> 
> The mcp2518fd is connected with 2 interrupt lines one "main" and one for rx frames. 
> 
> The problem is that for every frame received the interrupt handler is run twice, which is kind of expensive since it's a SPI call to the chip to check interrupt registers. 
> 
> To me it looks like the interrupt is fired again as soon as it's unmasked. Either because it's queued? or maybe not cleared internally?
> I have scoped the interrupt signal and its real good without any glitches. 
> 
> I'm currently running a yocto build:
> Linux botekcc 5.10.79-yocto-tiny #1 SMP Tue Nov 16 03:57:43 UTC 2021 armv7l armv7l armv7l GNU/Linux 
> 
> But the mcp251xfd driver is from net-next/master
> 
> mcp251xfd_irq is the irqhandler for the mcp2518fd and is added like this:
> err = request_threaded_irq(spi->irq, NULL, mcp251xfd_irq,
>                                    IRQF_SHARED | IRQF_ONESHOT,
>                                    dev_name(&spi->dev), priv);
> 

You haven't set a IRQF_TRIGGER flag, so you are getting the
"as-already-configured" behaviour, which on your setup is both edges?
Try adding IRQF_TRIGGER_RISING, IRQF_TRIGGER_FALLING, IRQF_TRIGGER_HIGH or
IRQF_TRIGGER_LOW, as appropriate to your use case, to your flags.

Cheers,
Kent.