linux-kernel - Re: [PATCH v2] net: macb: do not scan PHYs manually

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Date:	Thu, 28 Apr 2016 13:03:15 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Andrew Lunn <andrew@...n.ch>,
	Nathan Sullivan <nathan.sullivan@...com>
Cc:	Nicolas Ferre <nicolas.ferre@...el.com>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Alexandre Belloni <alexandre.belloni@...e-electrons.com>
Subject: Re: [PATCH v2] net: macb: do not scan PHYs manually

On 28/04/16 11:59, Andrew Lunn wrote:
> On Thu, Apr 28, 2016 at 01:55:27PM -0500, Nathan Sullivan wrote:
>> On Thu, Apr 28, 2016 at 08:43:03PM +0200, Andrew Lunn wrote:
>>>> I agree that is a valid fix for AT91, however it won't solve our problem, since
>>>> we have no children on the second ethernet MAC in our devices' device trees. I'm
>>>> starting to feel like our second MAC shouldn't even really register the MDIO bus
>>>> since it isn't being used - maybe adding a DT property to not have a bus is a
>>>> better option?
>>>
>>> status = "disabled"
>>>
>>> would be the unusual way.
>>>
>>>       Andrew
>>
>> Oh, sorry, I meant we use both MACs on Zynq, however the PHYs are on the MDIO
>> bus of the first MAC.  So, the second MAC is used for ethernet but not for MDIO,
>> and so it does not have any PHYs under its DT node.  It would be nice if there
>> were a way to tell macb not to bother with MDIO for the second MAC, since that's
>> handled by the first MAC.
> 
> Yes, exactly, add support for status = "disabled" in the mdio node.

Something like that, just so we do not have to sprinkle tests all other
the place:

diff --git a/drivers/of/of_mdio.c b/drivers/of/of_mdio.c
index b622b33dbf93..2f497790be1b 100644
--- a/drivers/of/of_mdio.c
+++ b/drivers/of/of_mdio.c
@@ -209,6 +209,10 @@ int of_mdiobus_register(struct mii_bus *mdio,
struct device_node *np)
        bool scanphys = false;
        int addr, rc;

+       /* Do not continue if the node is disabled */
+       if (!of_device_is_available(np))
+               return -EINVAL;
+
        /* Mask out all PHYs from auto probing.  Instead the PHYs listed in
         * the device tree are populated after the bus has been
registered */
        mdio->phy_mask = ~0;


> 
>> I guess a good longer-term solution to all these problems would be to treat the
>> MAC and MDIO as seperate devices, like davinci seems to be doing.
> 
> A few others do this as well, e.g. most Marvell devices.

Sometimes the MDIO registers are intertwinned with the Ethernet MAC
register space, which is something you can solve by handing just the
relevant portion of the MDIO register space to a separate driver (though
you need to watch out for two drivers calling request_mem_region on the
same register space).
-- 
Florian