netdev - Re: [PATCH] net: phy: Move interrupt check from phy_check to phy

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Message-ID: <704e7f37-2b94-7e1f-c42f-374254bc791c@cogentembedded.com>
Date:   Thu, 8 Mar 2018 22:41:04 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Brad Mouring <brad.mouring@...com>, Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: Move interrupt check from phy_check to
 phy_interrupt

Hello!

On 03/08/2018 01:50 AM, Brad Mouring wrote:

> If multiple phys share the same interrupt (e.g. a multi-phy chip),
> the first device registered is the only one checked as phy_interrupt
> will always return IRQ_HANDLED if the first phydev is not halted.
> Move the interrupt check into phy_interrupt and, if it was not this
> phydev, return IRQ_NONE to allow other devices on this irq a chance
> to check if it was their interrupt.

   Hm, looking at kernel/irq/handle.c, all registered IRQ handlers are always
called regardless of their results. Care to explain?

> Signed-off-by: Brad Mouring <brad.mouring@...com>
> ---
>  drivers/net/phy/phy.c | 16 ++++++----------
>  1 file changed, 6 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/net/phy/phy.c b/drivers/net/phy/phy.c
> index e3e29c2b028b..ff1aa815568f 100644
> --- a/drivers/net/phy/phy.c
> +++ b/drivers/net/phy/phy.c
> @@ -632,6 +632,12 @@ static irqreturn_t phy_interrupt(int irq, void *phy_dat)
>  	if (PHY_HALTED == phydev->state)
>  		return IRQ_NONE;		/* It can't be ours.  */
>  
> +	if (phy_interrupt_is_valid(phydev)) {

  Always true in this context, no?

> +		if (phydev->drv->did_interrupt &&
> +			!phydev->drv->did_interrupt(phydev))

   I don't think we can do this in the interrupt context as this function *will*
read from MDIO... I think that was the reason why IRQ handling is done in the
thread context... 

> +			return IRQ_NONE;
> +	}
> +
>  	phy_change(phydev);
>  
>  	return IRQ_HANDLED;
[...]

MBR, Sergei