netdev - Re: [PATCH net-next 0/2] Add mii_bus to ixgbe driver for dsa devs

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Message-ID: <35978a9e-e298-9e21-5768-47f1aac125b6@silicom-usa.com>
Date:   Thu, 29 Nov 2018 22:19:36 +0000
From:   Steve Douthit <stephend@...icom-usa.com>
To:     Jeff Kirsher <jeffrey.t.kirsher@...el.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 0/2] Add mii_bus to ixgbe driver for dsa devs

On 11/29/18 2:03 PM, Jeff Kirsher wrote:
> On Thu, 2018-11-29 at 18:54 +0000, Steve Douthit wrote:
>> Most dsa devices currently expect to get a pointer to a mii_bus from
>> platform data of device tree information.
>>
>> The first patch exposes a mii_bus for ixgbe devices.
>>
>> Currently the ixgbe driver only allows accesses to the probed PHY
>> address via ioctls. The second patch changes that behavior to allow
>> access to all addresses.  This should be useful for doing switch peeks &
>> pokes from userspace for development, test, or if theres no dsa driver
>> for a particular switch yet.
>>
>> I've tested the clause 22 portion of this code on a board that has an
>> Intel C3xxx series SoC connected to a Marvell Peridot switch.  I don't
>> have any clause 45 devices or other ixgbe devices to test with.
>>
>> Stephen Douthit (2):
>>    ixgbe: register a mdiobus
>>    ixgbe: use mii_bus to handle MII related ioctls
>>
>>   drivers/net/ethernet/intel/ixgbe/ixgbe.h      |   2 +
>>   drivers/net/ethernet/intel/ixgbe/ixgbe_main.c |  35 ++--
>>   drivers/net/ethernet/intel/ixgbe/ixgbe_phy.c  | 192 ++++++++++++++++++
>>   drivers/net/ethernet/intel/ixgbe/ixgbe_phy.h  |   2 +
>>   4 files changed, 216 insertions(+), 15 deletions(-)
>>
> 
> I will add these changes to my queue, please remember to send patches
> against the drivers in drivers/net/ethernet/intel/* to
> intel-wired-lan@...ts.osuosl.org  mailing list as well, so that our
> patchwork project can track the patches.

Sorry about that, I'll add it to the CC list for the next rev.

I started adding another board to the platform driver that needs this
code and found a bug.  The new board has more lanes enabled via soft
straps.  That caused sysfs to complain because I ended up with duplicate
bus IDs from this code:

+	/* Use the position of the device in the PCI hierarchy as the id */
+	snprintf(bus->id, MII_BUS_ID_SIZE, "%s-mdio-%s", ixgbe_driver_name,
+		 pci_name(pdev->bus->self));

Please drop this series for now.

Thinking about this some more I probably need to ensure that only a
single mii_bus is registered out of all the discovered x550em_a devices.
More generally there's not always going to be a 1:1 mapping between MACs
and MIIs on these devices and the code should handle that.

I think for the next rev I'll only register a single mii_bus for the
lowest numbered bus:device.function x500em_a device, and skip mii_bus
setup entirely for other device IDs.

Let me know if there's another/better way to tackle that.