netdev - Re: [PATCH] net: phy: realtek: clear interrupt during init for rtl8211f

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Date:   Wed, 17 Jun 2020 17:09:26 +0800
From:   Jisheng Zhang <Jisheng.Zhang@...aptics.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Russell King <linux@...linux.org.uk>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: phy: realtek: clear interrupt during init for
 rtl8211f

On Fri, 15 May 2020 19:30:38 +0200 Heiner Kallweit wrote:


> 
> 
> On 15.05.2020 18:18, Florian Fainelli wrote:
> >
> >
> > On 5/15/2020 12:41 AM, Jisheng Zhang wrote:  
> >> On Thu, 14 May 2020 21:50:53 +0200 Heiner Kallweit wrote:
> >>  
> >>>
> >>>
> >>> On 14.05.2020 08:25, Jisheng Zhang wrote:  
> >>>> On Wed, 13 May 2020 20:45:13 +0200 Heiner Kallweit wrote:
> >>>>  
> >>>>>
> >>>>> On 13.05.2020 08:51, Jisheng Zhang wrote:  
> >>>>>> Hi,
> >>>>>>
> >>>>>> On Tue, 12 May 2020 20:43:40 +0200 Heiner Kallweit wrote:
> >>>>>>  
> >>>>>>>
> >>>>>>>
> >>>>>>> On 12.05.2020 12:46, Jisheng Zhang wrote:  
> >>>>>>>> The PHY Register Accessible Interrupt is enabled by default, so
> >>>>>>>> there's such an interrupt during init. In PHY POLL mode case, the
> >>>>>>>> INTB/PMEB pin is alway active, it is not good. Clear the interrupt by
> >>>>>>>> calling rtl8211f_ack_interrupt().  
> >>>>>>>
> >>>>>>> As you say "it's not good" w/o elaborating a little bit more on it:
> >>>>>>> Do you face any actual issue? Or do you just think that it's not nice?  
> >>>>>>
> >>>>>>
> >>>>>> The INTB/PMEB pin can be used in two different modes:
> >>>>>> INTB: used for interrupt
> >>>>>> PMEB: special mode for Wake-on-LAN
> >>>>>>
> >>>>>> The PHY Register Accessible Interrupt is enabled by
> >>>>>> default, there's always such an interrupt during the init. In PHY POLL mode
> >>>>>> case, the pin is always active. If platforms plans to use the INTB/PMEB pin
> >>>>>> as WOL, then the platform will see WOL active. It's not good.
> >>>>>>  
> >>>>> The platform should listen to this pin only once WOL has been configured and
> >>>>> the pin has been switched to PMEB function. For the latter you first would
> >>>>> have to implement the set_wol callback in the PHY driver.
> >>>>> Or where in which code do you plan to switch the pin function to PMEB?  
> >>>>
> >>>> I think it's better to switch the pin function in set_wol callback. But this
> >>>> is another story. No matter WOL has been configured or not, keeping the
> >>>> INTB/PMEB pin active is not good. what do you think?
> >>>>  
> >>>
> >>> It shouldn't hurt (at least it didn't hurt for the last years), because no
> >>> listener should listen to the pin w/o having it configured before.
> >>> So better extend the PHY driver first (set_wol, ..), and then do the follow-up
> >>> platform changes (e.g. DT config of a connected GPIO).  
> >>
> >> There are two sides involved here: the listener, it should not listen to the pin
> >> as you pointed out; the phy side, this patch tries to make the phy side
> >> behave normally -- not keep the INTB/PMEB pin always active. The listener
> >> side behaves correctly doesn't mean the phy side could keep the pin active.
> >>
> >> When .set_wol isn't implemented, this patch could make the system suspend/resume
> >> work properly.
> >>
> >> PS: even with set_wol implemented as configure the pin mode, I think we
> >> still need to clear the interrupt for phy poll mode either in set_wol
> >> or as this patch does.  
> >
> > I agree with Jisheng here, Heiner, is there a reason you are pushing
> > back on the change? Acknowledging prior interrupts while configuring the
> > PHY is a common and established practice.
> >  
> First it's about the justification of the change as such, and second about the
> question whether the change should be in the driver or in phylib.
> 
> Acking interrupts we do already if the PHY is configured for interrupt mode,
> we call phy_clear_interrupt() at the beginning of phy_enable_interrupts()
> and at the end of phy_disable_interrupts().
> When using polling mode there is no strict need to ack interrupts.
> If we say however that interrupts should be acked in general, then I think
> it's not specific to RTL8211F, but it's something for phylib. Most likely
> we would have to add a call to phy_clear_interrupt() to phy_init_hw().

it's specific to RTL8211F from the following two PoV:
1. the PIN is shared between INTB and PMEB.
2. the PHY Register Accessible Interrupt is enabled by default

I didn't see such behaviors with other PHYs.

Thanks