Re: [PATCH] net: phy: micrel: Fix detection of ksz87xx switch

On Sat, Jul 31, 2021 at 08:19:17AM +1000, Steve Bennett wrote:

quoted

On 31 Jul 2021, at 2:59 am, Jakub Kicinski [off-list ref] wrote:

Please extend the CC list to the maintainers, and people who
worked on this driver in the past, especially Marek.

Sure, I can do that in a v2 of the patch along with the more detailed
explanation below.

quoted

On Fri, 30 Jul 2021 20:51:20 +1000 Steve Bennett wrote:

quoted

The previous logic was wrong such that the ksz87xx
switch was not identified correctly.

Any more details of what is happening? Which extact device do you see
this problem on?

I have a ksz8795 switch.

Without the patch:

ksz8795-switch spi3.1 ade1 (uninitialized): PHY [dsa-0.1:03] driver [Generic PHY]
ksz8795-switch spi3.1 ade2 (uninitialized): PHY [dsa-0.1:04] driver [Generic PHY]

With the patch:

ksz8795-switch spi3.1 ade1 (uninitialized): PHY [dsa-0.1:03] driver [Micrel KSZ87XX Switch]
ksz8795-switch spi3.1 ade2 (uninitialized): PHY [dsa-0.1:04] driver [Micrel KSZ87XX Switch]

[...]

And do the external ports work for you after this?

I have a development board with a KSZ8795.  All ports worked before
this patch.  After this patch, when I bring up the external ports they
are reported as having link up at 10M half duplex, when the link is
actually down.

The ksz8873mll_read_status() function is trying to read a non-standard
MDIO register that is not handled by the ksz8795 driver's MDIO
emulation (and is not documented as existing on the KSZ8873MLL,
either!).  It also also reports link up, which is obviously not
correct for an external port.

I'll post a patch as a reply to this.

Ben.

-- 
Ben Hutchings · Senior Embedded Software Engineer, Essensium-Mind · mind.be