Re: [PATCH v3 5/6] dt-bindings: net: dsa: make reset optional and add rgmii-mode to mt7531

On 08/05/2022 19:04, Peter Geis wrote:

On Sun, May 8, 2022 at 8:12 AM Frank Wunderlich [off-list ref] wrote:

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I think the issue is more for the description itself.

Devicetree is only meant to describe the hardware and does in general don't
care how any firmware (Linux-kernel, *BSD, etc) handles it. So going with
"the kernel does it this way" is not a valid reason for a binding change ;-) .

Exactly. The argument in commit msg was not matching the change, because
driver implementation should not be (mostly) a reason for such changes.

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Instead in general want to reason that there are boards without this reset
facility and thus make it optional for those.

if only the wording is the problem i try to rephrase it from hardware PoV.

maybe something like this?

https://github.com/frank-w/BPI-R2-4.14/commits/5.18-mt7531-mainline2/Documentation/devicetree/bindings/net/dsa/mediatek%2Cmt7530.yaml

Looks ok.

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Another way is maybe increasing the delay after the reset (to give more time all
come up again), but imho it is no good idea resetting the gmac/mdio-bus from the
child device.

have not looked into the gmac driver if this always  does the initial reset to
have a "clean state". In this initial reset the switch will be resetted too
and does not need an additional one which needs the gmac/mdio initialization
to be done again.

For clarification, the reset gpio line is purely to reset the phy.
If having the switch driver own the reset gpio instead of the gmac
breaks initialization that means there's a bug in the gmac driver
handling phy init.
In testing I've seen issues moving the reset line to the mdio node
with other phys and the stmmac gmac driver, so I do believe this is
the case.

Yes, this seems reasonable, although Frank mentioned that reset is
shared with gmac, so it resets some part of it as well?




Best regards,
Krzysztof