linux-kernel - Re: [PATCH] of_mdio: fix phy interrupt passing

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Message-ID: <53024D4B.9010103@codethink.co.uk>
Date:	Mon, 17 Feb 2014 17:56:27 +0000
From:	Ben Dooks <ben.dooks@...ethink.co.uk>
To:	Florian Fainelli <f.fainelli@...il.com>
CC:	Grant Likely <grant.likely@...aro.org>,
	linux-kernel@...ts.codethink.co.uk,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	Linux-sh list <linux-sh@...r.kernel.org>,
	Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
Subject: Re: [PATCH] of_mdio: fix phy interrupt passing

On 17/02/14 17:26, Florian Fainelli wrote:
> Hi Ben,
>
> 2014-02-17 8:29 GMT-08:00 Ben Dooks <ben.dooks@...ethink.co.uk>:
>> 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.
>
> The real bug fix, which is not properly explained here, is that
> irq_of_parse_and_map() should return values > 0 when the interrupt is
> valid, so this makes me wonder why we are not propagating the return
> value from irq_of_parse_and_map() in case the call to
> of_irq_parse_one() does return something non-zero?

	rc = irq_of_parse_and_map(child, 0);
	if (rc > 0) {
		mdio->irq[addr] = rc;
		phy->irq = rc;
	}

Unfortunately we do not get any idea of what error went wrong
when doing this, all we get it 0 on failure. So we cannot tell
if the problem was due to no interrupt being there or there was
an interrupt and it could not be parsed properly.

The best we can do is assume that the PHY is happy with being
polled and the specific driver will error out if it expects to
be able to work with an interrupt.

If we error out, we may end up stopping any PHYs where there is
no interrupt available from working. Also, if we fail to parse
then we can generally fall back to polling.

-- 
Ben Dooks				http://www.codethink.co.uk/
Senior Engineer				Codethink - Providing Genius
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