netdev - Re: [PATCH v2] net: phy: dp83867: perform soft reset and retain established link

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Date:   Mon, 14 Jun 2021 10:17:32 +0200
From:   Johannes Pointner <h4nn35.work@...il.com>
To:     "Bajjuri, Praneeth" <praneeth@...com>,
        Geet Modi <geet.modi@...com>, Andrew Lunn <andrew@...n.ch>
Cc:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] net: phy: dp83867: perform soft reset and retain
 established link

Hello Praneeth,

On Fri, Jun 11, 2021 at 7:05 PM Bajjuri, Praneeth <praneeth@...com> wrote:
>
> Hannes,
>
> On 6/10/2021 12:53 AM, Johannes Pointner wrote:
> > Hello,
> >
> > On Thu, Jun 10, 2021 at 6:10 AM Andrew Lunn <andrew@...n.ch> wrote:
> >>
> >> On Wed, Jun 09, 2021 at 07:43:42PM -0500, praneeth@...com wrote:
> >>> From: Praneeth Bajjuri <praneeth@...com>
> >>>
> >>> Current logic is performing hard reset and causing the programmed
> >>> registers to be wiped out.
> >>>
> >>> as per datasheet: https://www.ti.com/lit/ds/symlink/dp83867cr.pdf
> >>> 8.6.26 Control Register (CTRL)
> >>>
> >>> do SW_RESTART to perform a reset not including the registers,
> >>> If performed when link is already present,
> >>> it will drop the link and trigger re-auto negotiation.
> >>>
> >>> Signed-off-by: Praneeth Bajjuri <praneeth@...com>
> >>> Signed-off-by: Geet Modi <geet.modi@...com>
> >>
> >> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> >>
> >>      Andrew
> >
> > I reported a few days ago an issue with the DP83822 which I think is
> > caused by a similar change.
> > https://lore.kernel.org/netdev/CAHvQdo2yzJC89K74c_CZFjPydDQ5i22w36XPR5tKVv_W8a2vcg@mail.gmail.com/
> > In my case I can't get an link after this change, reverting it fixes
> > the problem for me.
>
> Are you saying that instead of reset if sw_restart is done as per this
> patch, there is no issue?
In my case(DP83822 connected to an i.MX6) if the digital(SW) restart
is used (Bit 14) I have the issue that I can' get a link.
ip addr shows:
1: lo: <LOOPBACK> mtu 65536 qdisc noop qlen 1000
   link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast qlen 1000
   link/ether 00:60:65:54:32:10 brd ff:ff:ff:ff:ff:ff

If I revert this back to using the SW reset (Bit 15) it works again.

Regards,
Hannes