Using ethtool or swconfig to change link settings for mt7620a?

Using ethtool or swconfig to change link settings for mt7620a?

[Daniel Santos]

Hello,

I need to change auto-negotiate, speed and duplex for a port on my
mt7620a-based device, but I'm not quite certain that I understand the
structure here.  When using ethtool on eth0 I always get ENODEV,
apparently because priv->phy_dev is always NULL in fe_get_link_ksettings
of drivers/net/ethernet/mtk/ethtool.c.  But I'm being told that eth0 is
only an internal device between the µC and the switch hardware, so it
isn't even the one I need to change.

If this is true, then it looks like I will need to implement a
get_port_link function for struct switch_dev_ops?  Can anybody confirm
this to be the case?  Also, are there any examples aside from the
Broadcom drivers?  I have the mt7620 programmer's guide and it specifies
the registers I need to change.

Thanks,
Daniel

Re: [OpenWrt-Devel] Using ethtool or swconfig to change link settings for mt7620a?

[Daniel Golle]

Hi Daniel,

On Sat, Jun 08, 2019 at 04:06:54AM -0500, Daniel Santos wrote:
> Hello,
> 
> I need to change auto-negotiate, speed and duplex for a port on my
> mt7620a-based device, but I'm not quite certain that I understand the
> structure here.  When using ethtool on eth0 I always get ENODEV,
> apparently because priv->phy_dev is always NULL in fe_get_link_ksettings
> of drivers/net/ethernet/mtk/ethtool.c.  But I'm being told that eth0 is
> only an internal device between the µC and the switch hardware, so it
> isn't even the one I need to change.

That's correct.

> If this is true, then it looks like I will need to implement a
> get_port_link function for struct switch_dev_ops?  Can anybody confirm
> this to be the case?  Also, are there any examples aside from the
> Broadcom drivers?  I have the mt7620 programmer's guide and it specifies
> the registers I need to change.

Currently MT7620 still uses our legacy swconfig switch driver, which
also doesn't support setting autoneg, speed and duplex. However, rather
than implementing it there, it'd be great to add support for the FE-
version of the MT7530 swtich found in the MT7620(A/N) WiSoC to the now
upstream DSA driver[1]. While this driver was originally intended for
use with standalone MT7530 GE switch chip or the ARM-based MT7623 SoC,
the same switch fabric is also implemented in MT7621 and support for
that chip was added to the driver recently[2]. MT7620 basically also
features the same switch internally, however, it comes with only one
CPU port, supports only FastEthernet and lacks some of the management
counters.

Assuming your MT7620 datasheet includes the decription of the MT7530
switch registers, it'd be great if you can help working on supporting
MT7620 in the DSA driver as well -- gaining per-port ethtool support
as a reward :)


Cheers


Daniel


[1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/dsa/mt7530.c
[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ddda1ac116c852bb969541ed53cffef7255c4961

Re: Using ethtool or swconfig to change link settings for mt7620a?

[Andrew Lunn]

On Sat, Jun 08, 2019 at 04:06:54AM -0500, Daniel Santos wrote:
> Hello,

Hi Daniel

As Daniel Golle pointed out, swconfig is an openwrt only
thing. Mainline people on netdev are unlikely to help you much. If you
do however decide to work on the mainline DSA driver, people here will
offer help, answers to questions, etc. The DSA driver will give you
full control of the per port PHY configuration via ethtool.

      Andrew

Re: [OpenWrt-Devel] Using ethtool or swconfig to change link settings for mt7620a?

[Daniel Santos]

Hello Daniel,

Thanks for your help!

On 6/8/19 6:51 AM, Daniel Golle wrote:
> Hi Daniel,
>
> On Sat, Jun 08, 2019 at 04:06:54AM -0500, Daniel Santos wrote:
>> Hello,
>>
>> I need to change auto-negotiate, speed and duplex for a port on my
>> mt7620a-based device, but I'm not quite certain that I understand the
>> structure here.  When using ethtool on eth0 I always get ENODEV,
>> apparently because priv->phy_dev is always NULL in fe_get_link_ksettings
>> of drivers/net/ethernet/mtk/ethtool.c.  But I'm being told that eth0 is
>> only an internal device between the µC and the switch hardware, so it
>> isn't even the one I need to change.
> That's correct.

It always helps when my idea about what I'm doing matches reality.

>> If this is true, then it looks like I will need to implement a
>> get_port_link function for struct switch_dev_ops?  Can anybody confirm
>> this to be the case?  Also, are there any examples aside from the
>> Broadcom drivers?  I have the mt7620 programmer's guide and it specifies
>> the registers I need to change.
> Currently MT7620 still uses our legacy swconfig switch driver, which
> also doesn't support setting autoneg, speed and duplex. However, rather
> than implementing it there, it'd be great to add support for the FE-
> version of the MT7530 swtich found in the MT7620(A/N) WiSoC to the now
> upstream DSA driver[1].

Ok, this makes much more sense now.  So swconfig is on its way out in
favor of DSA (which I've never heard of until now)?  I presume this will
also abstract away changes of ethtool to netlink-based instead of ioctl
on a random socket as well?

> While this driver was originally intended for
> use with standalone MT7530 GE switch chip or the ARM-based MT7623 SoC,
> the same switch fabric is also implemented in MT7621 and support for
> that chip was added to the driver recently[2]. MT7620 basically also
> features the same switch internally, however, it comes with only one
> CPU port, supports only FastEthernet and lacks some of the management
> counters.
>
> Assuming your MT7620 datasheet includes the decription of the MT7530
> switch registers, it'd be great if you can help working on supporting
> MT7620 in the DSA driver as well -- gaining per-port ethtool support
> as a reward :)

Wonderful!  So if I understand correctly, this is the same switch
hardware (internally at least), so has all of the same MAC and MII
registers on 7530, 7621, 7620, etc?  For now I have to get a fix for a
customer on a 3.18 kernel, so I'll be doing the swconfig first and then
see how much time we can put into the DSA implementation.

>
> Cheers
>
>
> Daniel
>
>
> [1]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/dsa/mt7530.c
> [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=ddda1ac116c852bb969541ed53cffef7255c4961
>

Also, would you happen to know why the mt7620 mdio driver is using a
32-bit read for MII registers that are 32-bit?  For example, in
_mt7620_mii_read.  It looks like some of this can use some improved
error management, since return codes are being ignored in a few places.

From what I can tell thus far, it looks like these MII registers are
standardized, so the "generic" version might do most or all of what I
need in some cases.  But as far as implementing DSA, I guess I'll have
to examine the mainlined driver and see how it works.  I just didn't
have a struct phy_device to work with when trying to get it to work.

Thanks,
Daniel