Subject: Re: [PATCH net,stable] phy: sfp: fix high power modules without diag mode

From: Bjørn Mork <[email-masked]>
Date: Mon, 06 Dec 2021 11:35:27 +0100

"Russell King (Oracle)" <[email-masked]> writes:
> On Fri, Dec 03, 2021 at 02:55:17PM +0100, Bjørn Mork wrote:
>> "Russell King (Oracle)" <[email-masked]> writes:
>> 
>> > Thinking a little more, how about this:
>> >
>> >  drivers/net/phy/sfp.c | 25 +++++++++++++++++++++----
>> >  1 file changed, 21 insertions(+), 4 deletions(-)
>> >
>> > diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
>> > index 51a1da50c608..4c900d063b19 100644
>> > --- a/drivers/net/phy/sfp.c
>> > +++ b/drivers/net/phy/sfp.c
>> > @@ -1752,17 +1752,20 @@ static int sfp_sm_probe_for_phy(struct sfp *sfp)
>> >  static int sfp_module_parse_power(struct sfp *sfp)
>> >  {
>> >  	u32 power_mW = 1000;
>> > +	bool supports_a2;
>> >  
>> >  	if (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_POWER_DECL))
>> >  		power_mW = 1500;
>> >  	if (sfp->id.ext.options & cpu_to_be16(SFP_OPTIONS_HIGH_POWER_LEVEL))
>> >  		power_mW = 2000;
>> >  
>> > +	supports_a2 = sfp->id.ext.sff8472_compliance !=
>> > +				SFP_SFF8472_COMPLIANCE_NONE ||
>> > +		      sfp->id.ext.diagmon & SFP_DIAGMON_DDM;
>> > +
>> >  	if (power_mW > sfp->max_power_mW) {
>> >  		/* Module power specification exceeds the allowed maximum. */
>> > -		if (sfp->id.ext.sff8472_compliance ==
>> > -			SFP_SFF8472_COMPLIANCE_NONE &&
>> > -		    !(sfp->id.ext.diagmon & SFP_DIAGMON_DDM)) {
>> > +		if (!supports_a2) {
>> >  			/* The module appears not to implement bus address
>> >  			 * 0xa2, so assume that the module powers up in the
>> >  			 * indicated mode.
>> > @@ -1779,11 +1782,24 @@ static int sfp_module_parse_power(struct sfp *sfp)
>> >  		}
>> >  	}
>> >  
>> > +	if (power_mW <= 1000) {
>> > +		/* Modules below 1W do not require a power change sequence */
>> > +		return 0;
>> > +	}
>> > +
>> > +	if (!supports_a2) {
>> > +		/* The module power level is below the host maximum and the
>> > +		 * module appears not to implement bus address 0xa2, so assume
>> > +		 * that the module powers up in the indicated mode.
>> > +		 */
>> > +		return 0;
>> > +	}
>> > +
>> >  	/* If the module requires a higher power mode, but also requires
>> >  	 * an address change sequence, warn the user that the module may
>> >  	 * not be functional.
>> >  	 */
>> > -	if (sfp->id.ext.diagmon & SFP_DIAGMON_ADDRMODE && power_mW > 1000) {
>> > +	if (sfp->id.ext.diagmon & SFP_DIAGMON_ADDRMODE) {
>> >  		dev_warn(sfp->dev,
>> >  			 "Address Change Sequence not supported but module requires %u.%uW, module may not be functional\n",
>> >  			 power_mW / 1000, (power_mW / 100) % 10);
>> 
>> Looks nice to me at least.  But I don't have the hardware to test it.
>
> I don't have the hardware either, so I can't test it - but it does need
> testing. I assume as you've reported it and sent a patch, you know
> someone who has run into this issue? It would be great if you could ask
> them to test it and let us know if it solves the problem.

Hello Teruyama!

Any chance you can test this proposed fix from Russel?  I believe it
should fix the issue with your NTT OCU SFP as well.

Bjørn