netdev - Re: i.mx6ul with DSA in multi chip addressing mode

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Message-ID: <d1181129-ec9d-01c1-3102-e1dc5dec0378@eks-engel.de>
Date:   Thu, 4 Jul 2019 10:54:47 +0200
From:   Benjamin Beckmeyer <beb@...-engel.de>
To:     Andrew Lunn <andrew@...n.ch>
CC:     <netdev@...r.kernel.org>
Subject: Re: i.mx6ul with DSA in multi chip addressing mode - no MDIO access


On 03.07.19 17:55, Andrew Lunn wrote:
> On Wed, Jul 03, 2019 at 03:10:34PM +0200, Benjamin Beckmeyer wrote:
>> Hey folks,
>>
>> I'm having a problem with a custom i.mx6ul board. When DSA is loaded I can't 
>> get access to the switch via MDIO, but the DSA is working properly. I set up
>> a bridge for testing and the switch is in forwarding mode and i can ping the 
>> board. But the MDIO access isn't working at address 2 for the switch. When I 
>> delete the DSA from the devicetree and start the board up, I can access the 
>> switch via MDIO.
>>
>> With DSA up and running:
>>
>> mii -i 2 0 0x9800
>> mii -i 2 1
>> phyid:2, reg:0x01 -> 0x4000
>> mii -i 2 0 0x9803
>> mii -i 2 1
>> phyid:2, reg:0x01 -> 0x4000
>> mii -i 2 1 0x1883
>> mii -i 2 1
>> phyid:2, reg:0x01 -> 0x4000
> Hi Benjamin
>
> I'm guessing that the driver is also using register 0 and 1 at the
> same time you are, e.g. to poll the PHYs for link status etc.
>
> There are trace points for MDIO, so you can get the kernel to log all
> registers access. That should confirm if i'm right.
>
> 	  Andrew

Hi Andrew,
you were absolutly right. The bus is really busy the whole time, I've 
checked that with the tracepoints in mdio_access.

But I'm still wondering why isn't that with a single chip addressing 
mode configured switch? I mean, okay, the switch has more ports, but
I've checked the accesses for both. The 6321(single chip addressing 
mode) has around 4-5 accesses to the MDIO bus and the 6390(multi chip 
addressing mode) has around 600 accesses per second. 

Thanks, 
Benjamin