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

From: "Russell King (Oracle)" <[email-masked]>
Date: Tue, 31 Mar 2026 15:05:28 +0100

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?

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!