On 1/24/22 08:56, Lars-Peter Clausen wrote:
On 1/24/22 08:12, Markus Mirevik wrote:
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.
I have tried with the IRQF_TRIGGGER_LOW flag as well. With same
result. i.e the interrupt is fired again as soon as the handler is
ready. Even if the interrupt line is deactivated.
However if I change the trigger to edge falling the interrupt will
only fire once. But his will inevitably lead to a missed edge
eventually.
Depending on how the mcp2518 GPIO controller works internally its
driver might have to use the handle_fasteoi_irq() flow to avoid this.
It is not uncommon to have hardware which needs a level IRQ acked
after the interrupt handler has run, rather than before like the
handle_level_irq() does. E.g.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/gpio/gpio-zynq.c?id=6dd859508336f0fd078fd62f3b9fe42a32aa38e2
- Lars
Sorry, I meant `Depending on how the am335x interrupt controller works...`
