linux-kernel - Re: [PATCH net-next v2 6/6] net: phy: microchip_t1s: add support for Microchip LAN865x Rev.B0 PHYs

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Message-ID: <349e1c57-24c6-46fa-b0ab-c6225ae1ece4@lunn.ch>
Date:   Mon, 22 May 2023 14:56:43 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Parthiban Veerasooran <Parthiban.Veerasooran@...rochip.com>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        ramon.nordin.rodriguez@...roamp.se, horatiu.vultur@...rochip.com,
        Woojung.Huh@...rochip.com, Nicolas.Ferre@...rochip.com,
        Thorsten.Kummermehr@...rochip.com
Subject: Re: [PATCH net-next v2 6/6] net: phy: microchip_t1s: add support for
 Microchip LAN865x Rev.B0 PHYs

> +static int lan865x_setup_cfgparam(struct phy_device *phydev)
> +{
> +	u16 cfg_results[5];
> +	u16 cfg_params[ARRAY_SIZE(lan865x_revb0_fixup_cfg_regs)];
> +	s8 offsets[2];
> +	int ret;

Reverse Christmas tree please.

> +
> +	ret = lan865x_generate_cfg_offsets(phydev, offsets);
> +	if (ret)
> +		return ret;
> +
> +	ret = lan865x_read_cfg_params(phydev, cfg_params);

Is this doing a read from fuses? Is anything documented about this?
What the values mean? Would a board designer ever need to use
different values? Or is this just a case of 'trust us', you don't need
to understand this magic.

> +	if (ret)
> +		return ret;
> +
> +	cfg_results[0] = (cfg_params[0] & 0x000F) |
> +			  FIELD_PREP(GENMASK(15, 10), 9 + offsets[0]) |
> +			  FIELD_PREP(GENMASK(15, 4), 14 + offsets[0]);
> +	cfg_results[1] = (cfg_params[1] & 0x03FF) |
> +			  FIELD_PREP(GENMASK(15, 10), 40 + offsets[1]);
> +	cfg_results[2] = (cfg_params[2] & 0xC0C0) |
> +			  FIELD_PREP(GENMASK(15, 8), 5 + offsets[0]) |
> +			  (9 + offsets[0]);
> +	cfg_results[3] = (cfg_params[3] & 0xC0C0) |
> +			  FIELD_PREP(GENMASK(15, 8), 9 + offsets[0]) |
> +			  (14 + offsets[0]);
> +	cfg_results[4] = (cfg_params[4] & 0xC0C0) |
> +			  FIELD_PREP(GENMASK(15, 8), 17 + offsets[0]) |
> +			  (22 + offsets[0]);
> +
> +	return lan865x_write_cfg_params(phydev, cfg_results);
> +}


	Andrew