Re: [PATCH net-next v5 0/4] phy: aquantia: Determine rate adaptation support from registers

From: Sean Anderson <sean.anderson@seco.com>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: Andrew Lunn <andrew@lunn.ch>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	netdev@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
	"David S . Miller" <davem@davemloft.net>,
	Paolo Abeni <pabeni@redhat.com>,
	linux-kernel@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	Tim Harvey <tharvey@gateworks.com>
Subject: Re: [PATCH net-next v5 0/4] phy: aquantia: Determine rate adaptation support from registers
Date: Thu, 5 Jan 2023 11:25:31 -0500	[thread overview]
Message-ID: <eb0f6eff-1456-1b59-b598-bff79cd749e1@seco.com> (raw)
In-Reply-To: <20230105133906.srx57bkfdl4ey32f@skbuf>

On 1/5/23 08:39, Vladimir Oltean wrote:
> Hi Sean,
> 
> On Tue, Jan 03, 2023 at 05:05:07PM -0500, Sean Anderson wrote:
>> This attempts to address the problems first reported in [1]. Tim has an
>> Aquantia phy where the firmware is set up to use "5G XFI" (underclocked
>> 10GBASE-R) when rate adapting lower speeds. This results in us
>> advertising that we support lower speeds and then failing to bring the
>> link up. To avoid this, determine whether to enable rate adaptation
>> based on what's programmed by the firmware. This is "the worst choice"
>> [2], but we can't really do better until we have more insight into
>> what the firmware is doing. At the very least, we can prevent bad
>> firmware from causing us to advertise the wrong modes.
> 
> After this patch set, is there any reason why phydev->rate_matching
> still exists and must be populated by the PHY driver?

It's necessary for phylink_link_up to know what speed to use for the MAC.

--Sean