linux-kernel - Re: [PATCH] net: mdio: of: Do not treat fixed-link as PHY

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Message-ID: <bd9f2507-958e-50bf-2b84-c21adf6ab588@microchip.com>
Date:   Tue, 31 Mar 2020 08:54:13 +0000
From:   <Codrin.Ciubotariu@...rochip.com>
To:     <f.fainelli@...il.com>, <andrew@...n.ch>
CC:     <netdev@...r.kernel.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <hkallweit1@...il.com>,
        <linux@...linux.org.uk>, <davem@...emloft.net>
Subject: Re: [PATCH] net: mdio: of: Do not treat fixed-link as PHY

On 30.03.2020 20:22, Florian Fainelli wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
> On 3/30/2020 9:30 AM, Andrew Lunn wrote:
>> On Mon, Mar 30, 2020 at 07:01:36PM +0300, Codrin Ciubotariu wrote:
>>> Some ethernet controllers, such as cadence's macb, have an embedded MDIO.
>>> For this reason, the ethernet PHY nodes are not under an MDIO bus, but
>>> directly under the ethernet node. Since these drivers might use
>>> of_mdiobus_child_is_phy(), we should fix this function by returning false
>>> if a fixed-link is found.
>>
>> So i assume the problem occurs here:
>>
>> static int macb_mdiobus_register(struct macb *bp)
>> {
>>          struct device_node *child, *np = bp->pdev->dev.of_node;
>>
>>          /* Only create the PHY from the device tree if at least one PHY is
>>           * described. Otherwise scan the entire MDIO bus. We do this to support
>>           * old device tree that did not follow the best practices and did not
>>           * describe their network PHYs.
>>           */
>>          for_each_available_child_of_node(np, child)
>>                  if (of_mdiobus_child_is_phy(child)) {
>>                          /* The loop increments the child refcount,
>>                           * decrement it before returning.
>>                           */
>>                          of_node_put(child);
>>
>>                          return of_mdiobus_register(bp->mii_bus, np);
>>                  }
>>
>>          return mdiobus_register(bp->mii_bus);
>> }
>>
>> I think a better solution is
>>
>>          for_each_available_child_of_node(np, child)
>> +             if (of_phy_is_fixed_link(child)
>> +                continue;
>>                  if (of_mdiobus_child_is_phy(child)) {
>>                          /* The loop increments the child refcount,
>>                           * decrement it before returning.
>>                           */
>>                          of_node_put(child);
>>
>>                          return of_mdiobus_register(bp->mii_bus, np);
>>                  }
>>
>>          return mdiobus_register(bp->mii_bus);
>> }
>>
>> This problem is only an issue for macb, so keep the fix local to macb.
> 
> Agree, there is no reason for of_mdiobus_child_is_phy() to be checking
> for a fixed-link. If you submit this formally:
> 
> Acked-by: Florian Fainelli <f.fainelli@...il.com>

Thanks guys. I thought there might be other controllers that have the 
PHY nodes inside the ethernet node. If not, I guess that 
of_mdiobus_child_is_phy() can be restricted to be called only if the 
passed device_node points to an MDIO node.
Moving the fix to macb, I think that of_phy_is_fixed_link() needs a 
device_node to the ethernet node, since it also has to deal with the 
legacy case in which fixed-link is a property, so it would look like 
something like this:
         struct device_node *child, *np = bp->pdev->dev.of_node;

+       if (of_phy_is_fixed_link(np))
+               return mdiobus_register(bp->mii_bus);
+
         /* Only create the PHY from the device tree if at least one PHY is

I will send another patch shortly.

Thanks and best regards,
Codrin