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From: Florian Fainelli <f.fainelli@gmail.com>
To: Alexandre Belloni <alexandre.belloni@bootlin.com>,
	Andrew Lunn <andrew@lunn.ch>
Cc: "David S . Miller" <davem@davemloft.net>,
	Allan Nielsen <Allan.Nielsen@microsemi.com>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: phy: allow scanning busses with missing phys
Date: Tue, 24 Apr 2018 09:37:09 -0700	[thread overview]
Message-ID: <2833f30a-cf95-e5c7-e44f-218929e61024@gmail.com> (raw)
In-Reply-To: <20180424160904.32457-1-alexandre.belloni@bootlin.com>



On 04/24/2018 09:09 AM, Alexandre Belloni wrote:
> Some MDIO busses will error out when trying to read a phy address with no
> phy present at that address. In that case, probing the bus will fail
> because __mdiobus_register() is scanning the bus for all possible phys
> addresses.
> 
> In case MII_PHYSID1 returns -EIO or -ENODEV, consider there is no phy at
> this address and set the phy ID to 0xffffffff which is then properly
> handled in get_phy_device().

Humm, why not have your MDIO bus implementation do the scanning itself
in a reset() callback, which happens before probing the bus, and based
on the results, set phy_mask accordingly such that only PHYs present are
populated?

My only concern with your change is that we are having a special
treatment for EIO and ENODEV, so we must make sure MDIO bus drivers are
all conforming to that.

> 
> Suggested-by: Andrew Lunn <andrew@lunn.ch>
> Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
> ---
>  drivers/net/phy/phy_device.c | 11 ++++++++++-
>  1 file changed, 10 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index ac23322a32e1..9e4ba8e80a18 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -535,8 +535,17 @@ static int get_phy_id(struct mii_bus *bus, int addr, u32 *phy_id,
>  
>  	/* Grab the bits from PHYIR1, and put them in the upper half */
>  	phy_reg = mdiobus_read(bus, addr, MII_PHYSID1);
> -	if (phy_reg < 0)
> +	if (phy_reg < 0) {
> +		/* if there is no device, return without an error so scanning
> +		 * the bus works properly
> +		 */
> +		if (phy_reg == -EIO || phy_reg == -ENODEV) {
> +			*phy_id = 0xffffffff;
> +			return 0;
> +		}
> +
>  		return -EIO;
> +	}
>  
>  	*phy_id = (phy_reg & 0xffff) << 16;
>  
> 

-- 
Florian

  reply	other threads:[~2018-04-24 16:37 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-24 16:09 Alexandre Belloni
2018-04-24 16:37 ` Florian Fainelli [this message]
2018-04-24 18:01   ` Andrew Lunn
2018-04-25  1:08     ` Florian Fainelli
2018-04-24 18:09   ` Alexandre Belloni
2018-04-25  1:09 ` Florian Fainelli
2018-04-25 17:01 ` David Miller

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