netdev - Re: [PATCH net-next v7 2/3] net: dsa: microchip: ksz8: Add function to configure ports with integrated PHYs

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Date: Mon, 27 Nov 2023 10:19:22 -0800
From: Florian Fainelli <f.fainelli@...il.com>
To: Oleksij Rempel <o.rempel@...gutronix.de>,
 "David S. Miller" <davem@...emloft.net>, Andrew Lunn <andrew@...n.ch>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Vladimir Oltean <olteanv@...il.com>,
 Woojung Huh <woojung.huh@...rochip.com>,
 Arun Ramadoss <arun.ramadoss@...rochip.com>,
 "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: kernel@...gutronix.de, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com
Subject: Re: [PATCH net-next v7 2/3] net: dsa: microchip: ksz8: Add function
 to configure ports with integrated PHYs

On 11/27/23 06:51, Oleksij Rempel wrote:
> This patch introduces the function 'ksz8_phy_port_link_up' to the
> Microchip KSZ8xxx driver. This function is responsible for setting up
> flow control and duplex settings for the ports that are integrated with
> PHYs.
> 
> The KSZ8795 switch supports asymmetric pause control, which can't be
> fully utilized since a single bit controls both RX and TX pause. Despite
> this, the flow control can be adjusted based on the auto-negotiation
> process, taking into account the capabilities of both link partners.
> 
> On the other hand, the KSZ8873's PORT_FORCE_FLOW_CTRL bit can be set by
> the hardware bootstrap, which ignores the auto-negotiation result.
> Therefore, even in auto-negotiation mode, we need to ensure that this
> bit is correctly set.
> 
> When auto-negotiation isn't in use, we enforce symmetric pause control
> for the KSZ8795 switch.
> 
> Please note, forcing flow control disable on a port while still
> advertising pause support isn't possible. While this scenario
> might not be practical or desired, it's important to be aware of this
> limitation when working with the KSZ8873 and similar devices.
> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> Reviewed-by: Simon Horman <simon.horman@...igine.com>

Reviewed-by: Florian Fainelli <florian.fainelli@...adcom.com>
-- 
Florian