Re: [PATCH 3/4] net: macb: Add pm runtime support

Andrew Lunn
2018-10-31T14:54:08Z

On Wed, Oct 31, 2018 at 09:10:22AM +0530, Harini Katakam wrote:
> From: Harini Katakam <harinik@xilinx.com>
>
> Add runtime pm functions and move clock handling there.
> If device is suspended and not a wake device, then return from
> mdio read/write functions without performing any action because
> the clocks are not active.
>
> Signed-off-by: Shubhrajyoti Datta <shubhrajyoti.datta@xilinx.com>
> Signed-off-by: Harini Katakam <harinik@xilinx.com>
> ---
> Changes from RFC:
> Updated pm get sync/put sync calls.
> Removed unecessary clk up in mdio helpers.

This last bit has me worried.

The MDIO bus is a shared bus with a life of its own. You can have
multiple PHYs and switches on it. The PHYs can for a different
Ethernet MAC. Switch drivers will expect to be able to address the
switch when the interface is down.

The FEC driver did something similar for a while. I had to make MDIO
read/write runtime PM aware, otherwise i could not access the Ethernet
switch hanging of its MDIO bus.

Andrew