Re: [PATCH net-next v4 06/11] net: stmmac: resetup XPCS according to the new interface mode

From: Choong Yong Liang <yong.liang.choong@linux.intel.com>
To: "Russell King (Oracle)" <linux@armlinux.org.uk>
Cc: Rajneesh Bhardwaj <irenic.rajneesh@gmail.com>,
	David E Box <david.e.box@linux.intel.com>,
	Hans de Goede <hdegoede@redhat.com>,
	Mark Gross <markgross@kernel.org>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Jose Abreu <Jose.Abreu@synopsys.com>,
	"David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Richard Cochran <richardcochran@gmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Jesper Dangaard Brouer <hawk@kernel.org>,
	John Fastabend <john.fastabend@gmail.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Heiner Kallweit <hkallweit1@gmail.com>,
	Philipp Zabel <p.zabel@pengutronix.de>,
	Andrew Halaney <ahalaney@redhat.com>,
	Serge Semin <fancer.lancer@gmail.com>,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	linux-stm32@st-md-mailman.stormreply.com,
	linux-arm-kernel@lists.infradead.org,
	platform-driver-x86@vger.kernel.org, linux-hwmon@vger.kernel.org,
	bpf@vger.kernel.org, Voon Wei Feng <weifeng.voon@intel.com>,
	Michael Sit Wei Hong <michael.wei.hong.sit@intel.com>,
	Lai Peter Jun Ann <jun.ann.lai@intel.com>,
	Abdul Rahim Faizal <faizal.abdul.rahim@intel.com>
Subject: Re: [PATCH net-next v4 06/11] net: stmmac: resetup XPCS according to the new interface mode
Date: Thu, 15 Feb 2024 11:14:27 +0800	[thread overview]
Message-ID: <9154ea9e-863b-49b3-8729-1ba077872bcc@linux.intel.com> (raw)
In-Reply-To: <Zbys2orOUikYxeOm@shell.armlinux.org.uk>

On 2/2/2024 4:50 pm, Russell King (Oracle) wrote:
>> Thank you for taking the time to review, got your concerns, and I'll address
>> the following concerns before submitting a new patch series:
>>
>> 1. Remove allow_switch_interface and have the PHY driver fill in
>> phydev->possible_interfaces.
> 
> Yes please.
> 

Hi Russell,

I regret to inform you that I didn't implement everything exactly as 
proposed in the new patch series. My intention was to simplify the series, 
focusing solely on managing SGMII and 2500BASE-X interface mode switching. 
The recommendation to have the PHY driver fill in 
"phydev->possible_interfaces" will be addressed in a separate patch 
submission. I hope this is acceptable.

In the new patch series, I removed "allow_switch_interface" patches. The 
current solution continues to work with PHYs that are C45 and follow the 
legacy path, such as Marvell Alaska 88E2110. For the upcoming patch series, 
I will implement "phydev->possible_interfaces" for C22 and C45 PHYs.

>> 2. Rework on the PCS to have similar implementation with the following patch
>> "net: macb: use .mac_select_pcs() interface"
>> (https://lore.kernel.org/netdev/E1n568J-002SZX-Gr@rmk-PC.armlinux.org.uk/T/).
> 
> mac_select_pcs() is about returning to phylink the PCS that the MAC
> needs to use for the specified interface mode, or NULL if no PCS is
> required, nothing more, nothing less.
> 
> Plase do not copy that mac_select_pcs() implementation - changing the
> "ops" underneath phylink is no longer permitted.
> 

Upon further examination, I discovered that no change is required for the 
"mac_select_pcs()" function; we can still use the same PCS. According to 
the XPCS datasheet, a soft reset is necessary to re-initiate Clause 37 
auto-negotiation when switching to SGMII interface mode. This is the only 
setting required for properly configuring the SGMII interface mode, and 
nothing extra is needed for 2500BASE-X configuration.

In the new patch series, I removed "mac_select_pcs()" related patches and 
added a "xpcs_soft_reset()" patch for the XPCS.