linux-kernel - Re: [PATCH net-next] net: dsa: lan9303: Do not disable switch fabric port 0 at .probe

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Message-Id: <20171026.174147.1810311288840630490.davem@davemloft.net>
Date:   Thu, 26 Oct 2017 17:41:47 +0900 (KST)
From:   David Miller <davem@...emloft.net>
To:     privat@...l-hjelmeland.no
Cc:     andrew@...n.ch, vivien.didelot@...oirfairelinux.com,
        f.fainelli@...il.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] net: dsa: lan9303: Do not disable switch
 fabric port 0 at .probe

From: Egil Hjelmeland <privat@...l-hjelmeland.no>
Date: Tue, 24 Oct 2017 17:14:10 +0200

> Make the LAN9303 work when lan9303_probe() is called twice.
> 
> For some unknown reason the LAN9303 switch fail to forward data when switch
> fabric port 0 TX is disabled during probe. (Write of LAN9303_MAC_TX_CFG_0
> in lan9303_disable_processing_port().)
> 
> In that situation the switch fabric seem to receive frames, because the ALR
> is learning addresses. But no frames are transmitted on any of the ports.
> 
> In our system lan9303_probe() is called twice, first time
> dsa_register_switch() return -EPROBE_DEFER. As an experiment, modified the
> code to skip writing LAN9303_MAC_TX_CFG_0, port 0 during the first probe.
> Then the switch works as expected.
> 
> Resolve the problem by not calling lan9303_disable_processing_port() on
> port 0 during probe. Ports 1 and 2 are still disabled.
> 
> Although unsatisfying that the exact failure mechanism is not known,
> the patch should not cause any harm.
> 
> Signed-off-by: Egil Hjelmeland <privat@...l-hjelmeland.no>

Applied.