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

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Date:   Tue, 23 Oct 2018 11:17:50 +0100
From:   Jose Abreu <jose.abreu@...opsys.com>
To:     Florian Fainelli <f.fainelli@...il.com>,
        Russell King - ARM Linux <linux@...linux.org.uk>,
        Jose Abreu <jose.abreu@...opsys.com>
CC:     Andrew Lunn <andrew@...n.ch>, <netdev@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Joao Pinto <joao.pinto@...opsys.com>
Subject: Re: [PATCH net-next 3/4] net: phy-c45: Implement reset/suspend/resume
 callbacks

On 22-10-2018 18:13, Florian Fainelli wrote:
> 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.

What about .suspend / .resume ?

Thanks and Best Regards,
Jose Miguel Abreu