linux-kernel - Re: Re: [PATCH v3 12/13] arm64: dts: mediatek: mt7988a-bpi-r4: add sfp cages and link to gmac

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Message-ID: <e1a49ca7-f082-4983-89fe-1a8f8c8a3de1@lunn.ch>
Date: Tue, 10 Jun 2025 14:58:44 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Frank Wunderlich <frank-w@...lic-files.de>
Cc: linux@...web.de, myungjoo.ham@...sung.com, kyungmin.park@...sung.com,
	cw00.choi@...sung.com, djakov@...nel.org, robh@...nel.org,
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	linux-mediatek@...ts.infradead.org
Subject: Re: Re: [PATCH v3 12/13] arm64: dts: mediatek: mt7988a-bpi-r4: add
 sfp cages and link to gmac

> > sff,sfp.yaml says:
> > 
> >   maximum-power-milliwatt:
> >     minimum: 1000
> >     default: 1000
> >     description:
> >       Maximum module power consumption Specifies the maximum power consumption
> >       allowable by a module in the slot, in milli-Watts. Presently, modules can
> >       be up to 1W, 1.5W or 2W.
> > 
> > I've no idea what will happen when the SFP core sees 3000. Is the
> > comment out of date?
> 
> at least sfp-core has no issue with the setting
> 
> root@...-r4-phy-8G:~# dmesg | grep sfp
> [    1.269437] sfp sfp1: Host maximum power 3.0W
> [    1.613749] sfp sfp1: module CISCO-FINISAR    FTLX8571D3BCL-C2 rev A    sn S2209167650      dc 220916  
> 
> imho some modules require more than 2W (some gpon/xpon and 10G copper ethernet).

Looking at the code:

static int sfp_module_parse_power(struct sfp *sfp)
{
        u32 power_mW = 1000;
        bool supports_a2;

        if (sfp->id.ext.sff8472_compliance >= SFP_SFF8472_COMPLIANCE_REV10_2 &&
            sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_POWER_DECL))
                power_mW = 1500;
        /* Added in Rev 11.9, but there is no compliance code for this */
        if (sfp->id.ext.sff8472_compliance >= SFP_SFF8472_COMPLIANCE_REV11_4 &&
            sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_HIGH_POWER_LEVEL))
                power_mW = 2000;

How does your module indicate it needs 3000 mW? Does this bit of code
need extending to read additional bits?

	Andrew