linux-kernel - Re: [PATCH 1/2] net: phy: adin: clear the diag clock and set LINKING

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Date:   Wed, 21 Oct 2020 17:05:28 +0300
From:   Alexandru Ardelean <ardeleanalex@...il.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     Alexandru Ardelean <alexandru.ardelean@...log.com>,
        netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        alexaundru.ardelean@...log.com,
        Heiner Kallweit <hkallweit1@...il.com>, linux@...linux.org.uk,
        David Miller <davem@...emloft.net>, kuba@...nel.org
Subject: Re: [PATCH 1/2] net: phy: adin: clear the diag clock and set
 LINKING_EN during autoneg

On Wed, Oct 21, 2020 at 4:58 PM Andrew Lunn <andrew@...n.ch> wrote:
>
> On Wed, Oct 21, 2020 at 04:51:39PM +0300, Alexandru Ardelean wrote:
> > The LINKING_EN bit is always cleared during reset. Initially it was set
> > during the downshift setup, because it's in the same register as the
> > downshift retry count (PHY_CTRL1).
>
> Hi Alexandru
>
> For those of us how have not read the datasheet, could you give a
> brief explanation what LINKING_EN does?

So, clearing this bit puts the PHY in a standby-state.
The PHY doesn't do any autonegotiation or link handling.

>
> > This change moves the handling of LINKING_EN from the downshift handler to
> > the autonegotiation handler. Also, during autonegotiation setup, the
> > diagnostics clock is cleared.
>
> And what is the diagnostics clock used for?

The clock diagnostics is used for 2 things: the diagnostics block
[mostly for stuff like cable-diagnostics] and the frame-generator.
The frame-generator is an interesting feature of the PHY, that's not
useful for the current phylib; the PHY can send packages [like a
signal generator], and then these can be looped back, or sent over the
wire.
Maybe it's being used mostly internally by the group that created the PHY

Having said this, I'll include some comments for these in a V2 of this patchset.

>
>     Andrew