Re: lan78xx: WARNING: irq 79 handler enabled interrupts

On Sat, 29 Dec 2018 00:02:57 +0000,
Stefan Wahren [off-list ref] wrote:

Hi Stephan,

Hi,
while booting my Raspberry Pi 3 B+ with Linux 4.20 (arm64/defconfig)
i'm getting the following warning:

[   11.005738] irq 79 handler irq_default_primary_handler+0x0/0x8 enabled interrupts

[...]

This seems to come from the lan78xx driver, because i don't get this
warning on the RPI 3B (smsc95xx).

What's the approach to fix this issue?  Is it just simply replace
spin_lock_irq() with spin_lock_irqsave() at the right places?

No, this is more pathological than that. The USB framework seems to be
using threaded interrupts, which implies that interrupts are
re-enabled as soon as it has run.

In turn, this driver is using handle_simple_irq() as its flow, which
definitely expect interrupts to be disabled.

I have no insight in how this driver works, but I'm happy to help if
someone explains the interrupt flow of this thing.

	M.

-- 
Jazz is not dead, it just smell funny.