linux-kernel - Re: [PATCH v7 3/3] net: stmmac: dwmac-sophgo: Add phy interface filter

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Message-ID: <g2tqvcw7ocewzbqy7txz6sumdxeelhl4jk2s3btnnijyt572di@nrfcac6grpvn>
Date: Tue, 11 Nov 2025 06:26:32 +0800
From: Inochi Amaoto <inochiama@...il.com>
To: Simon Horman <horms@...nel.org>, Inochi Amaoto <inochiama@...il.com>
Cc: Han Gao <rabenda.cn@...il.com>, Icenowy Zheng <uwu@...nowy.me>, 
	Vivian Wang <wangruikang@...as.ac.cn>, Yao Zi <ziyao@...root.org>, 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>, 
	Chen Wang <unicorn_wang@...look.com>, Maxime Coquelin <mcoquelin.stm32@...il.com>, 
	Alexandre Torgue <alexandre.torgue@...s.st.com>, Heiner Kallweit <hkallweit1@...il.com>, 
	Russell King <linux@...linux.org.uk>, "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>, 
	netdev@...r.kernel.org, devicetree@...r.kernel.org, sophgo@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com, 
	linux-arm-kernel@...ts.infradead.org, Yixun Lan <dlan@...too.org>, Longbin Li <looong.bin@...il.com>, 
	Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v7 3/3] net: stmmac: dwmac-sophgo: Add phy interface
 filter

On Mon, Nov 10, 2025 at 08:09:10PM +0000, Simon Horman wrote:
> On Fri, Nov 07, 2025 at 07:17:15PM +0800, Inochi Amaoto wrote:
> > As the SG2042 has an internal rx delay, the delay should be removed
> > when initializing the mac, otherwise the phy will be misconfigurated.
> > 
> > Fixes: 543009e2d4cd ("net: stmmac: dwmac-sophgo: Add support for Sophgo SG2042 SoC")
> > Signed-off-by: Inochi Amaoto <inochiama@...il.com>
> > Tested-by: Han Gao <rabenda.cn@...il.com>
> > Reviewed-by: Andrew Lunn <andrew@...n.ch>
> > ---
> >  .../ethernet/stmicro/stmmac/dwmac-sophgo.c    | 20 ++++++++++++++++++-
> >  1 file changed, 19 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/dwmac-sophgo.c b/drivers/net/ethernet/stmicro/stmmac/dwmac-sophgo.c
> 
> ...
> 
> > @@ -50,11 +56,23 @@ static int sophgo_dwmac_probe(struct platform_device *pdev)
> >  	if (ret)
> >  		return ret;
> >  
> > +	data = device_get_match_data(&pdev->dev);
> > +	if (data && data->has_internal_rx_delay) {
> > +		plat_dat->phy_interface = phy_fix_phy_mode_for_mac_delays(plat_dat->phy_interface,
> > +									  false, true);
> > +		if (plat_dat->phy_interface == PHY_INTERFACE_MODE_NA)
> > +			return -EINVAL;
> 
> I'm sorry if this is a false positive. Because, more so than Russell [1], I
> confused about how about the treatment of phy_interface. But it seems that
> there is a miss match between the use of phy_fix_phy_mode_for_mac_delays()
> above and the binding.
> 
> The call to phy_fix_phy_mode_for_mac_delays() above will return
> PHY_INTERFACE_MODE_NA unless phy_interface is PHY_INTERFACE_MODE_RGMII_ID
> or PHY_INTERFACE_MODE_RGMII_RXID.
> 
>   phy_interface_t phy_fix_phy_mode_for_mac_delays(phy_interface_t interface,
> 						bool mac_txid, bool mac_rxid)
>   ...
> 	if (mac_rxid) {
> 		if (interface == PHY_INTERFACE_MODE_RGMII_ID)
> 			return PHY_INTERFACE_MODE_RGMII_TXID;
> 		if (interface == PHY_INTERFACE_MODE_RGMII_RXID)
> 			return PHY_INTERFACE_MODE_RGMII;
> 		return PHY_INTERFACE_MODE_NA;
> 	}
>   ...
> 
> Looking at phy_modes(), unsurprisingly, the following mappings occur:
> * "rgmii" -> PHY_INTERFACE_MODE_RGMII
> * "rgmii-id" -> PHY_INTERFACE_MODE_RGMII_ID
> * "rgmii-rxid" -> PHY_INTERFACE_MODE_RGMII_RXID
> * "rgmii-txid" -> PHY_INTERFACE_MODE_RGMII_TXID
> 
> And in the binding, patch 1/3 of this series, only phy-mode rgmii-txid or
> rgmii-id is allowed.
> 

rgmii-txid is a mistake and should be rgmii-rxid. This is because
the mac of SG2042 add rx delay, and the phy can only add tx delay or
no delay. So the phy-mode can only be rgmii-id or rgmii-rxid. I will
fix it in the next version.

> But if rgmii-txid is used, PHY_INTERFACE_MODE_RGMII_TXID will be passed to
> phy_fix_phy_mode_for_mac_delays(), which will return PHY_INTERFACE_MODE_NA.
> 
> Again, I'm confused about the mapping in phy_fix_phy_mode_for_mac_delays().
> But there does seem to be some inconsistency between the binding and
> the driver implementation here.
> 

I think this inconsistency begin with the change for ethernet-controller
binding.
https://lore.kernel.org/all/20250430-v6-15-rc3-net-rgmii-delays-v2-1-099ae651d5e5@lunn.ch/

And this function serves as an helper so the driver can only add
the delay once.

> Flagged by Claude Code with https://github.com/masoncl/review-prompts/ 
> 
> [1] https://lore.kernel.org/all/aPSubO4tJjN_ns-t@shell.armlinux.org.uk/
> 
> ...

Regards,
Inochi