Hi Florian, On Fri, Mar 01, 2019 at 07:08:56PM -0800, Florian Fainelli wrote: > On 3/1/2019 7:07 AM, Antoine Tenart wrote: > > On Fri, Mar 01, 2019 at 03:19:53PM +0100, Andrew Lunn wrote: > >> On Fri, Mar 01, 2019 at 12:00:47PM +0100, Antoine Tenart wrote: > >>> When the Marvell 10G PHYs are set out of reset, the LPOWER bit is set > >>> depending on an hardware configuration choice. We also do not know what > >>> is the PHY state at boot time. Hence, set the PHY in low power by > >>> default when this driver probes. > >> > >> Florian did some work for c22 PHYs so that the existing link state > >> could be used at boot. So for example, the bootloader configured the > >> PHY up and it got link, there is no need to down/up the PHY when linux > >> takes control. The networking comes up faster that way. > >> > >> Can this work for this PHY? > > > > This use case (the bootloader configures the PHY, Linux boots and sets > > an interface using this PHY up) would work, and is what's happening in > > some situations right now (the 3310 reset is never asserted prior to > > this series). > > > > But consider this case (let's say we use a 10G link): > > > > ---------------- ---------------- > > | Board 1 | | Board 2 | > > | MAC — 3310 — | — SFP cable — | — 3310 — MAC | > > ---------------- ---------------- > > > > Board 1: The userspace do not set the interface up. The MAC is in reset > > (default state during the MAC driver probe), the PHY was > > configured by the bootloader. > > Board 2: The userspace set the interface up. The MAC is configured, the > > PHY is configured as well. > > > > The two PHY's PCS will establish a link and report it as being up. In > > this case, phylink's AN mode is MLO_AN_PHY and thus will report the > > overall link as being the PHY's link status: up. > > > > My understanding is that the issue arises because the PHYs were never > > set in reset, or low power, and thus act as if the user wanted the port > > to be up. As the default behaviour for networking ports is to be down at > > boot, I thought to set the PHY as well in a default low power state. > > The policy you are creating here for the marvell10g driver is entirely > applicable to any PHY <=> PHY configuration where either of the two > software agents on Board 1 or Board 2 has not had a chance to bring-up > its bootloader/OS/applications to control the PHY.
Right. > A number of PHYs come up fully on (or in isolate or super isolate mode) > and will AN with their link partner if connected. For some people it's a > feature, for some it is a waste of power. I don't necessarily have an > issue with your patch per-se, but it does create an one off behavior > that other PHY drivers may not follow. I agree having a per-driver behaviour is not something we want. As I understand it, there is no behaviour enforced currently regarding this matter. I agree both cases have their pros and cons: - It's weird to have an interface reporting being UP when it's not really. - Having the link come up faster can be a feature. I have some questions then: - Do you think calling suspend() in the core when probing a PHY driver would work for all PHYs? - Would a new Kconfig option selecting the default behaviour at boot time be a solution? - Or this is a WONTFIX kind of (small) issues? :) Thanks! Antoine -- Antoine Ténart, Bootlin Embedded Linux and Kernel engineering https://bootlin.com
