netdev - Re: [PATCH net] dsa: mv88e6xxx: Ensure all pending interrupts are handled prior to exit

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Date:   Tue, 12 Feb 2019 00:33:27 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     John David Anglin <dave.anglin@...l.net>
Cc:     Russell King <linux@....linux.org.uk>,
        Vivien Didelot <vivien.didelot@...oirfairelinux.com>,
        Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH net] dsa: mv88e6xxx: Ensure all pending interrupts are
 handled prior to exit

> Signed-off-by:  John David Anglin <dave.anglin@...l.net>
> ---
>  drivers/net/dsa/mv88e6xxx/chip.c | 28 ++++++++++++++++++++++------
>  1 file changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/drivers/net/dsa/mv88e6xxx/chip.c b/drivers/net/dsa/mv88e6xxx/chip.c
> index 8dca2c949e73..12fd7ce3f1ff 100644
> --- a/drivers/net/dsa/mv88e6xxx/chip.c
> +++ b/drivers/net/dsa/mv88e6xxx/chip.c
> @@ -261,6 +261,7 @@ static irqreturn_t mv88e6xxx_g1_irq_thread_work(struct mv88e6xxx_chip *chip)
>  	unsigned int sub_irq;
>  	unsigned int n;
>  	u16 reg;
> +	u16 ctl1;
>  	int err;
> 
>  	mutex_lock(&chip->reg_lock);
> @@ -270,13 +271,28 @@ static irqreturn_t mv88e6xxx_g1_irq_thread_work(struct mv88e6xxx_chip *chip)
>  	if (err)
>  		goto out;
> 
> -	for (n = 0; n < chip->g1_irq.nirqs; ++n) {
> -		if (reg & (1 << n)) {
> -			sub_irq = irq_find_mapping(chip->g1_irq.domain, n);
> -			handle_nested_irq(sub_irq);
> -			++nhandled;
> +	do {
> +		for (n = 0; n < chip->g1_irq.nirqs; ++n) {
> +			if (reg & (1 << n)) {
> +				sub_irq = irq_find_mapping(chip->g1_irq.domain,
> +							   n);
> +				handle_nested_irq(sub_irq);
> +				++nhandled;
> +			}
>  		}
> -	}
> +
> +		mutex_lock(&chip->reg_lock);
> +		err = mv88e6xxx_g1_read(chip, MV88E6XXX_G1_CTL1, &ctl1);
> +		if (err)
> +			goto unlock;
> +		err = mv88e6xxx_g1_read(chip, MV88E6XXX_G1_STS, &reg);
> +unlock:
> +		mutex_unlock(&chip->reg_lock);
> +		if (err)
> +			goto out;
> +		ctl1 &= GENMASK(chip->g1_irq.nirqs, 0);
> +	} while (reg & ctl1);

Hi David

I just tested this on one of my boards. It loops endlessly:

[   47.173396] mv88e6xxx_g1_irq_thread_work: c881 a8 80                         
[   47.182108] mv88e6xxx_g1_irq_thread_work: c881 a8 80                         
[   47.190820] mv88e6xxx_g1_irq_thread_work: c881 a8 80                         
[   47.199535] mv88e6xxx_g1_irq_thread_work: c881 a8 80                         
[   47.208254] mv88e6xxx_g1_irq_thread_work: c881 a8 80   

These are reg, ctl1, reg & ctl1.

So there is an unhandled device interrupt. I think this is because
device interrupts are not masked before installing the interrupt
handler. But i've not fully got to the bottom of this yet.

	 Andrew