Re: [PATCH v2 2/2] arm64: dts: renesas: ulcb: Remove renesas,no-ether-link property

On Fri, Dec 22, 2017 at 09:32:56AM +0100, Simon Horman wrote:

On Thu, Dec 21, 2017 at 05:18:59PM +0200, Vladimir Zapolskiy wrote:

quoted

From: Bogdan Mirea <redacted>

The present change is a bug fix for AVB link iteratively up/down.

Steps to reproduce:
- start AVB TX stream (Using aplay via MSE),
- disconnect+reconnect the eth cable,
- after a reconnection the eth connection goes iteratively up/down
  without user interaction,
- this may heal after some seconds or even stay for minutes.

As the documentation specifies, the "renesas,no-ether-link" option
should be used when a board does not provide a proper AVB_LINK signal.
There is no need for this option enabled on RCAR H3/M3 Salvator-X/XS
and ULCB starter kits since the AVB_LINK is correctly handled by HW.

Choosing to keep or remove the "renesas,no-ether-link" option will
have impact on the code flow in the following ways:
- keeping this option enabled may lead to unexpected behavior since
  the RX & TX are enabled/disabled directly from adjust_link function
  without any HW interrogation,
- removing this option, the RX & TX will only be enabled/disabled after
  HW interrogation. The HW check is made through the LMON pin in PSR
  register which specifies AVB_LINK signal value (0 - at low level;
  1 - at high level).

In conclusion, the present change is also a safety improvement because
it removes the "renesas,no-ether-link" option leading to a proper way
of detecting the link state based on HW interrogation and not on
software heuristic.

Fixes: 253ed045a34d ("arm64: dts: renesas: Extract common ULCB board support")

The above shuffles the code around but does not introduce the problem
as far as I can see. Instead I think we should use:

Fixes: 144bf6ccb13f ("arm64: dts: h3ulcb: enable EthernetAVB")
Fixes: 883fae315a6a ("arm64: dts: m3ulcb: enable EthernetAVB")

quoted

Signed-off-by: Bogdan Mirea <redacted>
Signed-off-by: Vladimir Zapolskiy <redacted>

I have applied this a fix for v4.15 with the updated Fixes tags above. 
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