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

[Y.b. Lu]

Hi Richard,

> -----Original Message-----
> From: Richard Cochran <richardcochran@xxxxxxxxx>
> Sent: Wednesday, March 25, 2020 9:42 PM
> To: Y.b. Lu <yangbo.lu@xxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; David S . Miller
> <davem@xxxxxxxxxxxxx>; Vladimir Oltean <vladimir.oltean@xxxxxxx>;
> Claudiu Manoil <claudiu.manoil@xxxxxxx>; Andrew Lunn <andrew@xxxxxxx>;
> Vivien Didelot <vivien.didelot@xxxxxxxxx>; Florian Fainelli
> <f.fainelli@xxxxxxxxx>; Alexandre Belloni <alexandre.belloni@xxxxxxxxxxx>;
> Microchip Linux Driver Support <UNGLinuxDriver@xxxxxxxxxxxxx>
> 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