netdev - Re: [PATCH net-next v5 5/6] net: tn40xx: add mdio bus support

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Date: Wed, 8 May 2024 20:25:43 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Hans-Frieder Vogt <hfdevel@....net>
Cc: FUJITA Tomonori <fujita.tomonori@...il.com>, netdev@...r.kernel.org,
	horms@...nel.org, kuba@...nel.org, jiri@...nulli.us,
	pabeni@...hat.com
Subject: Re: [PATCH net-next v5 5/6] net: tn40xx: add mdio bus support

> > +    writel(((1 << 15) | i), regs + TN40_REG_MDIO_CMD);
> 
> similarly here:
> 
> writel((MDIO_PHY_ID_C45 | i), regs + TN40_REG_MDIO_CMD);

This one i don't agree with. It happens to work, but there is no
reason to think the hardware has been designed around how Linux
combines the different parts of a C45 address into one word, using the
top bit to indicate it is actually a C45 address, not a C22.

I would much prefer a TN40_ define is added for this bit.

> > +    writel(((device & 0x1F) | ((port & 0x1F) << 5)),
> 
> and also here, similarly:
> 
> writel((device & MDIO_PHY_ID_DEVAD) | ((port << 5) & MDIO_PHY_ID_PRTAD),

Similarly here, this happens to work, but that is just because the
hardware matches a software construct Linux uses. It would be better
to add TN40_ macros to describe the hardware.

   Andrew