netdev - Re: [PATCH v3 net-next 3/6] net: dsa: felix: unconditionally configure MAC speed to 1000Mbps

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Date:   Sun, 5 Jul 2020 14:08:41 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>, davem@...emloft.net,
        netdev@...r.kernel.org
Cc:     andrew@...n.ch, vivien.didelot@...il.com, claudiu.manoil@....com,
        alexandru.marginean@....com, ioana.ciornei@....com,
        linux@...linux.org.uk
Subject: Re: [PATCH v3 net-next 3/6] net: dsa: felix: unconditionally
 configure MAC speed to 1000Mbps



On 7/5/2020 9:16 AM, Vladimir Oltean wrote:
> From: Vladimir Oltean <vladimir.oltean@....com>
> 
> In VSC9959, the PCS is the one who performs rate adaptation (symbol
> duplication) to the speed negotiated by the PHY. The MAC is unaware of
> that and must remain configured for gigabit. If it is configured at
> OCELOT_SPEED_10 or OCELOT_SPEED_100, it'll start transmitting PAUSE
> frames out of control and never recover, _even if_ we then reconfigure
> it at OCELOT_SPEED_1000 afterwards.
> 
> This patch fixes a bug that luckily did not have any functional impact.
> We were writing 10, 100, 1000 etc into this 2-bit field in
> DEV_CLOCK_CFG, but the hardware expects values in the range 0, 1, 2, 3.
> So all speed values were getting truncated to 0, which is
> OCELOT_SPEED_2500, and which also appears to be fine.
> 
> Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian