RE: [PATCH v4 3/5] net: lan743x: Add support to software-nodes for SFP

[<Thangaraj.S@microchip.com>]

Hi Andrew,
Thanks for the comments.

> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: Thursday, May 14, 2026 6:28 PM
> To: Thangaraj Samynathan - I53494 <Thangaraj.S@microchip.com>
> Cc: netdev@vger.kernel.org; andrew+netdev@lunn.ch;
> davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> pabeni@redhat.com; Bryan Whitehead - C21958
> <Bryan.Whitehead@microchip.com>; UNGLinuxDriver
> <UNGLinuxDriver@microchip.com>; linux@armlinux.org.uk; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH v4 3/5] net: lan743x: Add support to software-nodes for
> SFP
> 
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> 
> > +#define PCI11X1X_TX_FAULT_GPIO               46
> > +#define PCI11X1X_TX_DIS_GPIO         47
> > +#define PCI11X1X_RATE_SEL0_GPIO              48
> > +#define PCI11X1X_LOS_GPIO            49
> > +#define PCI11X1X_MOD_DEF0_GPIO               51
> 
> How do you know these values?
> 
> Can i buy this device, design my own board, and decide to use a different
> mapping of GPIO pins to SFP cage pins? Or does the data sheet say you MUST
> use this mapping?
> 
> Maybe consider drivers/misc/lan966x_pci.dtso.
[Thangaraj Samynathan] ]  These values are from the Microchip EVB reference design,
not mandated   by the datasheet. A board designer is free to wire SFP signals to
different GPIO pins.

However, the PCI11x1x is a PCIe add-in card that can also be used in
standard x86 systems. A .dtso overlay has no base DT to attach to on
x86, and ACPI _DSD properties require the platform firmware vendor to
add them - which is not realistic for a PCIe add-in card in the field.

We propose using the EVB default GPIO values as a fallback when no
firmware description is present, and reading from DT/ACPI _DSD when
available. Does this approach seem reasonable?
 
> 
>       Andrew