Re: [PATCH net-next v3 2/2] net: mdio: add a driver for PIC64-HPSC/HX MDIO controller

Andrew Lunn
2026-03-31T14:21:13Z

On Tue, Mar 31, 2026 at 03:05:28PM +0100, Russell King (Oracle) wrote:
> On Tue, Mar 31, 2026 at 06:42:02AM -0700, Charles Perry wrote:
> > I don't know if there's any value in waiting for write completion here as
> > write completion doesn't mean that the effects of the write are available
> > right now. I also didn't run into any issues in my testing. Let me know if
> > you know of a use case where this wouldn't work.
> >
> > I can add a wait for transaction completion if that's expected by phylib.
>
> Consider a PHY using a shared interrupt line, and the interrupt being
> disabled in at the PHY before being torn down... wouldn't we want the
> write to the register which enables interrupts to complete before we
> unregister the interrupt handler for the particular PHY?
>
> I do notice that other MDIO drivers don't wait. Some PHY drivers don't
> access the PHY after the write to disable interrupts either. So, maybe
> phy_free_interrupt() should read-back from the PHY before calling
> free_irq() to guarantee that the write has completed?
>
> Andrew?

The general pattern is to not wait on write.

Interrupts is not a case i've thought about. Yes, a read to flush the
write would make sense, maybe in phy_disable_interrupts().

Andrew