Re: [PATCH net-next 3/4] net: phy-c45: Implement reset/suspend/resume callbacks

[Florian Fainelli <f.fainelli@gmail.com>]

On 10/22/18 8:48 AM, Russell King - ARM Linux wrote:
> On Mon, Oct 22, 2018 at 01:47:48PM +0100, Jose Abreu wrote:
>> Hello,
>>
>> On 22-10-2018 13:28, Andrew Lunn wrote:
>>>>  EXPORT_SYMBOL_GPL(gen10g_resume);
>>>> @@ -327,7 +381,7 @@ struct phy_driver genphy_10g_driver = {
>>>>  	.phy_id         = 0xffffffff,
>>>>  	.phy_id_mask    = 0xffffffff,
>>>>  	.name           = "Generic 10G PHY",
>>>> -	.soft_reset	= gen10g_no_soft_reset,
>>>> +	.soft_reset	= gen10g_soft_reset,
>>>>  	.config_init    = gen10g_config_init,
>>>>  	.features       = 0,
>>>>  	.aneg_done	= genphy_c45_aneg_done,
>>> Hi Jose
>>>
>>> You need to be careful here. There is a reason this is called
>>> gen10g_no_soft_reset, rather than having an empty
>>> gen10g_soft_reset. Some PHYs break when you do a reset.  So adding a
>>> gen10g_soft_reset is fine, but don't change this here, without first
>>> understanding the history, and talking to Russell King.
>>
>> Hmm, the reset function only interacts with standard PCS
>> registers, which should always be available ...
>>
>> >From my tests I need to do at least 1 reset during power-up so in
>> ultimate case I can add a feature quirk or similar.
>>
>> Russell, can you please comment ?
> 
> Setting the reset bit on 88x3310 causes the entire device to become
> completely inaccessible until hardware reset.  Therefore, this bit
> must _never_ be set for these devices.  That said, we have a separate
> driver for these PHYs, but that will only be used for them if it's
> present in the kernel.  If we accidentally fall back to the generic
> driver, then we'll screw the 88x3310 until a full hardware reset.
> 
> We also have a bunch of net devices that make use of this crippled
> "generic" 10G support - we don't know whether resetting the PHY
> for those systems will cause a regression - maybe board firmware
> already configured the PHY?  I can't say either way on that, except
> that we've had crippled 10G support in PHYLIB for a number of years
> now _with_ users, and adding reset support drastically changes the
> subsystem's behaviour for these users.
> 
> I would recommend not touching the generic 10G driver, but instead
> implement your own driver for your PHY to avoid causing regressions.
> 

Agreed.
-- 
Florian