Messages in this thread | | | Date | Thu, 9 Nov 2023 09:46:19 +0000 | From | "Russell King (Oracle)" <> | Subject | Re: [PATCH net 1/1] net: stmmac: fix MAC and phylink mismatch issue after resume with STMMAC_FLAG_USE_PHY_WOL enabled |
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On Thu, Nov 09, 2023 at 09:15:36AM +0000, Russell King (Oracle) wrote: > On Thu, Nov 09, 2023 at 01:00:27PM +0800, Gan Yi Fang wrote: > > From: "Gan, Yi Fang" <yi.fang.gan@intel.com> > > > > The issue happened when flag STMMAC_FLAG_USE_PHY_WOL is enabled. > > It can be reproduced with steps below: > > 1. Advertise only one speed on the host > > 2. Enable the WoL on the host > > 3. Suspend the host > > 4. Wake up the host > > > > When the WoL is disabled, both the PHY and MAC will suspend and wake up > > with everything configured well. When WoL is enabled, the PHY needs to be > > stay awake to receive the signal from remote client but MAC will enter > > suspend mode. > > > > When the MAC resumes from suspend, phylink_resume() will call > > phylink_start() to start the phylink instance which will trigger the > > phylink machine to invoke the mac_link_up callback function. The > > stmmac_mac_link_up() will configure the MAC_CTRL_REG based on the current > > link state. Then the stmmac_hw_setup() will be called to configure the MAC. > > > > This sequence might cause mismatch of the link state between MAC and > > phylink. This patch moves the phylink_resume() after stmamc_hw_setup() to > > ensure the MAC is initialized before phylink is being configured. > > Isn't this going to cause problems? > > stmamc_hw_setup() calls stmmac_init_dma_engine(), which then calls > stmmac_reset() - and stmmac_reset() can fail if the PHY clock isn't > running, which is why phylink_resume() gets called before this.
I think these two commits should be reviewed to understand why the code is the way it is, and why changing it may cause regressions:
90702dcd19c0 ("net: stmmac: fix MAC not working when system resume back with WoL active")
36d18b5664ef ("net: stmmac: start phylink instance before stmmac_hw_setup()")
As part of my work on stmmac that got junked, I was looking at a solution to the "we need the PHY clock to be running for the MAC to work for things like reset" problem - but those patches got thrown away when stmmac folk were very nitpicky over %u vs %d in format strings to print what was a _signed_ value that stmmac code stupidly converts to an unsigned integer... it's still a signed integer no matter if code decides to use "unsigned int". I suspect all those patches (and there was a considerable number of them) have now been expired from git, so are now totally lost, and honestly I have no desire to put further work into stmmac stuff.
-- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!
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