Re: [PATCH] net: mdio-gpio: support access that may sleep

[Sergei Shtylyov]

On 04/24/2015 08:36 PM, Florian Fainelli wrote:

> > > > > Some systems using mdio-gpio may use gpio on message based busses,
> > > > > which
> > > > > require sleeping (e.g. gpio from an I2C I/O expander).

> > > > > Since this driver does not use IRQ handler, it is safe to use the
> > > > > _cansleep suffixed gpio accessors.

> > > > > Signed-off-by: Vivien Didelot <vivien.didelot@xxxxxxxxxxxxxxxxxxxx>

> > > > Since this is down underneath the layer of an MII bus, you cannot
> > > > universally say that these routines are always called in a sleepable
> > > > context.

> > > > The PHY layer, and the driver itself above that, might call these
> > > > routines from timers, interruptes etc.

> > > The PHY library calls these routines from its state machine workqueue
> > > for that reason, or from process context (when invoked via ethtool
> > > ioctl). The only special case is phy_mac_interrupt() which is callable
> > > from interrupt context,

> >     It is not (as we have discussed recently) -- cancel_work_sync() may
> > sleep.

> True, but that does not invalidate my comment, I meant to write that
> this is the only function that you *might* potentially want to call from
> interrupt context,

   Sure, I did want that. :-)

> and yet it does not trigger low-level I/O accesses to
> the underlying MDIO bus, but instead uses the PHY library state machine
> workqueue to do that.

   That's so.

> Thanks for the reminder though, that needs fixing ;)

   Hopefully it's fixable... I had to use GPIO interrupt for AVB_PHY_INT pin 
since I didn't want to create a thread just to call phy_mac_interrupt().

> --
> Florian

WBR, Sergei

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