Messages in this thread | | | Date | Wed, 20 Mar 2024 10:13:55 -0700 | Subject | Re: [PATCH net v3 2/2] net: fec: Suspend the PHY on probe | From | Florian Fainelli <> |
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On 3/20/2024 9:54 AM, Russell King (Oracle) wrote: > On Wed, Mar 20, 2024 at 03:25:54PM +0000, John Ernberg wrote: >> Hi Russel, > > Growl. Hi Peter. > >> What we really want is the PHY to be suspended on suspend to RAM >> regardless of us having had an initial link up or not. > > So what you're asking is for the PHY to be suspended when the system > is entering suspend, which is a long time after the system booted and > thus phy_probe() was called, and could be some time before the system > resumes. > > I'm not sure what the relevance is of phy_probe() that was brought up > previously then. > >> This worked prior to 4c0d2e96ba05 ("net: phy: consider that suspend2ram >> may cut >> off PHY power") which was added in Linux 5.11, and 557d5dc83f68 ("net: >> fec: use >> mac-managed PHY PM") which was added in Linux 5.12. > > Looking at the former commit, that looks to me like it is only > affecting the resume paths, not the suspend paths, so wouldn't have > any impact itself on what happens when suspend happens. > > The latter commit states that it is a work around for an issue with a > particular PHY. What happens if you revert just this commit, does your > problem then go away? > > Also, please clarify. It seems that you are reporting a regression - > it used to work for you prior to 557d5dc83f68, but 557d5dc83f68 stops > it working for you? > >> Since FEC requires mac_managed_pm the generic PM suspend-resume paths >> are not >> taken. The resume sequencing with generic PM has been broken with the >> FEC since >> generic PM of the mdio bus was added, as the FEC will do phy_start() >> (via FEC >> resume) and then generic PM runs phy_init_hw() via mdio bus resume >> (previously: >> less damaging phy_resume()) due to how the FEC IP block works. > > That suggests that even with 557d5dc83f68 reverted, it's broken. > Digging into the history, what you're referring to dates from January > 2016, so are you reporting a regression that occured 8 _years_ ago, > at which point I'd question why it's taken 8 years. > > Given the time that has passed, I don't think reverting commits is > a sane approach. Quite what the right solution is though, I'm not > sure. > > From the description and the commits pointed to, I just don't see > that there is anything that could've changed with respect to the first > boot - if that has changed, then I think more research into what caused > it is needed. > > If it's the subsequent state after a suspend-resume cycle, then yes, > I would agree that its possible that these changes broke this for you. > Would clearing ndev->phydev->mac_managed_pm just before > phy_disconnect() in fec_enet_close() fix it for you, so the suspend/ > resume paths for the PHY get used when the network interface is down? > > Maybe, however, that's something that should happen in any case inside > phylib on phy_disconnect() as a matter of course, since the PHY will > at that point be no longer under the control of the network driver for > PM purposes. Could you give this idea a try please? >
On phy_disconnect() we will do a phy_detach() which calls phy_suspend(). Given that phy_disconnect() is called from fec_enet_close(), we still have a MDIO bus registered and we are not trying to suspend the MDIO bus, so we should have an effective phy_suspend() call here, what am I missing? -- Florian
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