netdev - Re: [PATCH 4/4] net: stmmac: Add glue layer for Sophgo SG2044 SoC

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Message-ID: <d691a687-c0e2-48a9-bf76-d0a086aa7870@lunn.ch>
Date: Wed, 23 Oct 2024 03:08:52 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Inochi Amaoto <inochiama@...il.com>
Cc: Chen Wang <unicorn_wang@...look.com>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Inochi Amaoto <inochiama@...look.com>,
	Alexandre Torgue <alexandre.torgue@...s.st.com>,
	Jose Abreu <joabreu@...opsys.com>,
	Maxime Coquelin <mcoquelin.stm32@...il.com>,
	Richard Cochran <richardcochran@...il.com>,
	Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>,
	Giuseppe Cavallaro <peppe.cavallaro@...com>,
	Yixun Lan <dlan@...too.org>, netdev@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-stm32@...md-mailman.stormreply.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-riscv@...ts.infradead.org
Subject: Re: [PATCH 4/4] net: stmmac: Add glue layer for Sophgo SG2044 SoC

On Wed, Oct 23, 2024 at 08:41:36AM +0800, Inochi Amaoto wrote:
> On Tue, Oct 22, 2024 at 03:51:08PM +0200, Andrew Lunn wrote:
> > On Tue, Oct 22, 2024 at 06:21:49PM +0800, Inochi Amaoto wrote:
> > > On Mon, Oct 21, 2024 at 03:27:18PM +0200, Andrew Lunn wrote:
> > > > > It is related to the RGMII delay. On sg2044, when the phy 
> > > > > sets rx-delay, the interal mac is not set the same delay, 
> > > > > so this is needed to be set.
> > > > 
> > > > This is the wrong way to do it. Please look at how phy-mode should be
> > > > used, the four different "rgmii" values. Nearly everybody gets this
> > > > wrong, so there are plenty of emails from me in the netdev list about
> > > > how it should be done.
> > > > 
> > > 
> > > The phy-mode is alreay set to the "rgmii-id" and a rx delay is already
> > > set (a default tx delay is set by the phy driver). In the scenario 
> > > the extra bit is used to fix 2ns difference between the sampling clock
> > > and data. It is more like an extra setting and the kernel can not handle
> > > it by only setting the phy-mode.
> > 
> > This sounds wrong.
> > 
> > So in DT you have rgmii-id? You say the PHY is doing TX delay. So you
> > pass PHY_INTERFACE_MODE_RGMII_TXID to the PHY? It is not clear from
> > this patch, i don't see any code mentioning
> > PHY_INTERFACE_MODE_RGMII_TXID. Could you point me at that code.
> > 
> > 	Andrew
> 
> The phy on the board I have is YT8531, The config code is here:
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/net/phy/motorcomm.c#n868

This PHY should be able to do rgmii-id, so there is no need for the
MAC to add delays. We encourage that setup in linux, so all RGMII
MAC/PHY pairs are the same, the PHY add the delays.

	Andrew