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

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Message-ID: <d027e5cc-f6a4-4a1b-066d-10c298472c3a@gmail.com>
Date:   Mon, 17 Jan 2022 15:49:40 +0100
From:   Christian Lamparter <chunkeey@...il.com>
To:     "Russell King (Oracle)" <linux@...linux.org.uk>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        Bjørn Mork <bjorn@...k.no>,
        netdev@...r.kernel.org,
        照山周一郎 <teruyama@...ingboard-inc.jp>
Subject: Re: [PATCH net,stable] phy: sfp: fix high power modules without diag
 mode

On 17/01/2022 15:24, Russell King (Oracle) wrote:
> On Sat, Jan 15, 2022 at 05:58:43PM +0100, Christian Lamparter wrote:
>> On 03/12/2021 13:58, Russell King (Oracle) wrote:
>>> On Fri, Dec 03, 2021 at 11:54:57AM +0000, Russell King (Oracle) wrote:
>>> [...]
>>> 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);
>>>
>>
>> The reporter has problems reaching you. But from what I can tell in his reply to his
>> OpenWrt Github PR:
>> <https://github.com/openwrt/openwrt/pull/4802#issuecomment-1013439827>
>>
>> your approach is working perfectly. Could you spin this up as a fully-fledged patch (backports?)
> 
> There seems to be no problem - I received an email on the 30 December
> complete with the test logs. However, that was during the holiday period
> and has been buried, so thanks for the reminder.
> 
> However, I'm confused about who the reporter and testers actually are,
> so I'm not sure who to put in the Reported-by and Tested-by fields.
>  From what I can see, Bjørn Mork <bjorn@...k.no> reported it (at least
> to mainline devs), and the fix was tested by 照山周一郎
> <teruyama@...ingboard-inc.jp>.
> 
> Is that correct? Thanks.
> 

 From what I know, you are correct there. 照山周一郎 posted a patch
"skip hpower setting for the module which has no revs" to fix his
issue to the OpenWrt-Devel Mailinglist on the 28th November 2021:
<https://www.mail-archive.com/openwrt-devel@lists.openwrt.org/msg60669.html>

|
|@@ -0,0 +1,12 @@
|@@ -0,0 +1,11 @@
|--- a/drivers/net/phy/sfp.c
|+++ b/drivers/net/phy/sfp.c
|@@ -1590,6 +1590,8 @@ static int sfp_module_parse_power(struct
|
| static int sfp_sm_mod_hpower(struct sfp *sfp, bool enable)
| {
|+      if (sfp->id.ext.sff8472_compliance == SFP_SFF8472_COMPLIANCE_NONE)
|+              return 0;
|       u8 val;
|       int err;

Bjørn Mork picked this up and noted:
|This looks like a workaround for a specific buggy module.  Is that
|correct?   Why not update sfp_module_parse_power() instead so you can
|skip the HPOWER state completely?  And add an appropriate warning about
|this unexpected combination of options and sff8472_compliance..."

and the thread went from there, with Bjørn Mork notifying you/upstream
about the problem because of the language barrier.

<https://www.mail-archive.com/openwrt-devel@lists.openwrt.org/msg60697.html>

| 照山周一郎 <teruy...@...ingboard-inc.jp> writes:
|
|> Thank you for your quick response.
|> It worked without any problems.
|
|Thanks for testing! I submitted this to netdev with a stable hint now.
|So it should end up in Linux v5.10.x, and therefore also OpenWrt, in a
|few weeks unless there are objections.

So, one could argue that both reported this in a way and 照山周一郎 tested
it on his hardware.

Cheers,
Christian (got to catch a train)