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

[Andrew Lunn <andrew@lunn.ch>]

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