linux-kernel - RE: [PATCH 6/6] ptp_ocelot: support 4 programmable pins

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Message-ID: <AM7PR04MB68853749A1196B30C917A232F8CF0@AM7PR04MB6885.eurprd04.prod.outlook.com>
Date:   Thu, 26 Mar 2020 09:34:52 +0000
From:   "Y.b. Lu" <yangbo.lu@....com>
To:     Richard Cochran <richardcochran@...il.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Vladimir Oltean <vladimir.oltean@....com>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>
Subject: RE: [PATCH 6/6] ptp_ocelot: support 4 programmable pins

Hi Richard,

> -----Original Message-----
> From: Richard Cochran <richardcochran@...il.com>
> Sent: Wednesday, March 25, 2020 9:42 PM
> To: Y.b. Lu <yangbo.lu@....com>
> Cc: linux-kernel@...r.kernel.org; netdev@...r.kernel.org; David S . Miller
> <davem@...emloft.net>; Vladimir Oltean <vladimir.oltean@....com>;
> Claudiu Manoil <claudiu.manoil@....com>; Andrew Lunn <andrew@...n.ch>;
> Vivien Didelot <vivien.didelot@...il.com>; Florian Fainelli
> <f.fainelli@...il.com>; Alexandre Belloni <alexandre.belloni@...tlin.com>;
> Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>
> Subject: Re: [PATCH 6/6] ptp_ocelot: support 4 programmable pins
> 
> On Wed, Mar 25, 2020 at 03:08:46AM +0000, Y.b. Lu wrote:
> 
> > The calling should be like this,
> > ptp_set_pinfunc (hold pincfg_mux)
> > ---> ptp_disable_pinfunc
> >    ---> .enable
> >       ---> ptp_find_pin (hold pincfg_mux)
> 
> I see.  The call
> 
>     ptp_disable_pinfunc() --> .enable()
> 
> is really
> 
>     ptp_disable_pinfunc() --> .enable(on=0)
> 
> or disable.
> 
> All of the other drivers (except mv88e6xxx which has a bug) avoid the
> deadlock by only calling ptp_find_pin() when invoked by .enable(on=1);
> 
> Of course, that is horrible, and I am going to find a way to fix it.

Thanks a lot.
Do you think it is ok to move protection into ptp_set_pinfunc() to protect just pin_config accessing?
ptp_disable_pinfunc() not touching pin_config could be out of protection.
But it seems indeed total ptp_set_pinfunc() should be under protection...

> 
> For now, maybe you can drop the "programmable pins" feature for your
> driver?  After all, the pins are not programmable.

I still want to confirm, did you mean the deadlock issue? Or you thought the pin supports only PTP_PF_PEROUT in hardware?
I could modify commit messages to indicate the pin supports both PTP_PF_PEROUT and PTP_PF_EXTTS, and PTP_PF_EXTTS support will be added in the future.
Thanks a lot.

> 
> Thanks,
> Richard