netdev - Re: [PATCH] of_mdio: fix phy interrupt passing

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Message-Id: <20140218170202.424D7C40517@trevor.secretlab.ca>
Date:	Tue, 18 Feb 2014 17:02:02 +0000
From:	Grant Likely <grant.likely@...aro.org>
To:	Ben Dooks <ben.dooks@...ethink.co.uk>
Cc:	linux-kernel@...ts.codethink.co.uk, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	linux-sh@...r.kernel.org, sergei.shtylyov@...entembedded.com
Subject: Re: [PATCH] of_mdio: fix phy interrupt passing

On Tue, 18 Feb 2014 09:40:39 +0000, Ben Dooks <ben.dooks@...ethink.co.uk> wrote:
> On 18/02/14 09:30, Grant Likely wrote:
> > On Mon, 17 Feb 2014 16:29:40 +0000, Ben Dooks <ben.dooks@...ethink.co.uk> wrote:
> >> The of_mdiobus_register_phy() is not setting phy->irq this causing
> >> some drivers to incorrectly assume that the PHY does not have an
> >> IRQ associated with it or install an interrupt handler for the
> >> PHY.
> >>
> >> Simplify the code setting irq and set the phy->irq at the same
> >> time so that the case if mdio->irq is not NULL is easier to read.
> >>
> >> This fixes the issue:
> >>   net eth0: attached PHY 1 (IRQ -1) to driver Micrel KSZ8041RNLI
> >>
> >> to the correct:
> >>   net eth0: attached PHY 1 (IRQ 416) to driver Micrel KSZ8041RNLI
> >>
> >> Signed-off-by: Ben Dooks <ben.dooks@...ethink.co.uk>
> >> ---
> >>   drivers/of/of_mdio.c | 12 ++++++------
> >>   1 file changed, 6 insertions(+), 6 deletions(-)
> >>
> >> diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
> >> index 875b7b6..7b3e7b0 100644
> >> --- a/drivers/of/of_mdio.c
> >> +++ b/drivers/of/of_mdio.c
> >> @@ -44,7 +44,7 @@ static int of_mdiobus_register_phy(struct mii_bus *mdio, struct device_node *chi
> >>   {
> >>   	struct phy_device *phy;
> >>   	bool is_c45;
> >> -	int rc, prev_irq;
> >> +	int rc;
> >>   	u32 max_speed = 0;
> >>
> >>   	is_c45 = of_device_is_compatible(child,
> >> @@ -55,11 +55,11 @@ static int of_mdiobus_register_phy(struct mii_bus *mdio, struct device_node *chi
> >>   		return 1;
> >>
> >>   	if (mdio->irq) {
> >> -		prev_irq = mdio->irq[addr];
> >> -		mdio->irq[addr] =
> >> -			irq_of_parse_and_map(child, 0);
> >> -		if (!mdio->irq[addr])
> >> -			mdio->irq[addr] = prev_irq;
> >
> > I cannot for the life for me remeber why the code was structured that
> > way. Your change is better.
> >
> >> +		rc = irq_of_parse_and_map(child, 0);
> >> +		if (rc > 0) {
> >> +			mdio->irq[addr] = rc;
> >> +			phy->irq = rc;
> >> +		}
> >>   	}
> >
> > The outer if is merely protecting against no irq array being allocated
> > for the bus. Would not the following be better:
> >
> > 	rc = irq_of_parse_and_map(child, 0);
> > 	if (rc > 0) {
> > 		phy->irq = rc;
> > 		if (mdio->irq)
> > 			mdio->irq[addr] = rc;
> > 	}
> 
> Thanks, that makes sense, although we've both failed to work
> out if mdio->irq is set, and rc <= 0 case, so:
> 
>   	rc = irq_of_parse_and_map(child, 0);
>   	if (rc > 0) {
>   		phy->irq = rc;
>   		if (mdio->irq)
>   			mdio->irq[addr] = rc;
>   	} else {
> 		if (mdio->irq)
> 			phy->irq = mdio->irq[addr];
> 	}

Is this actually a valid thing to do? I think the only time mdio->irq[]
is non-zero is when it is set to PHY_POLL. Is it valid to set phy->irq
to PHY_POLL? I didn't think it was.

g.

> 
> I think that covers all cases. This does rely on mdio->irq
> being initialised to PHY_POLL if allocated.
> 
> Once this is in, it may be easier then to not allocate
> mdio->irq for the OF case by default unless the driver
> registering the PHY knows it has the interrupt number(s)
> for the PHY already.
> 
> -- 
> Ben Dooks				http://www.codethink.co.uk/
> Senior Engineer				Codethink - Providing Genius

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