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Message-Id: <20230810225109.13973-1-alexandru.gagniuc@hp.com> Date: Thu, 10 Aug 2023 22:51:09 +0000 From: Alexandru Gagniuc <alexandru.gagniuc@...com> To: stern@...land.harvard.edu Cc: alexandru.gagniuc@...com, bjorn@...k.no, davem@...emloft.net, edumazet@...gle.com, eniac-xw.zhang@...com, hayeswang@...ltek.com, jflf_kernel@....com, kuba@...nel.org, linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org, netdev@...r.kernel.org, pabeni@...hat.com, stable@...r.kernel.org, svenva@...omium.org Subject: Re: [PATCH v2] r8152: Suspend USB device before shutdown when WoL is enabled On Thu, Aug 10, 2023 at 01:34:39PM -0400, Alan Stern wrote: > On Thu, Aug 10, 2023 at 04:22:16PM +0000, Alexandru Gagniuc wrote: > > On Wed, Aug 02, 2023 at 11:23:46AM -0400, Alan Stern wrote: > > > > > > Indeed. And I am asking how you can be sure the host controller driver > > > (or some other part of the software stack) doesn't have this bug. > > > > The only way that I have to show that is empirical. I observe that WoL from S5 > > does not work on a device with an r8153 chip. I apply the change, and verify > > that WoL from S5 now works in this scenario. What are you thinking of in terms > > of being sure no current or future bug exists? > > I was thinking that the host controller driver's shutdown method might > turn off power to all of the ports. > > For example, in the ehci-hcd driver, ehci_shutdown() calls > ehci_silence_controller(), which calls ehci_turn_off_all_ports(). I > don't know if xhci-hcd does anything similar. EHCI is a different beast. I don't think EHCI (USB2.0) has the U3 link state. The equivalent for would be xhci_shutdown(). It makes a call to usb_disable_xhci_ports() for XHCI_SPURIOUS_REBOOT quirk. As I have not encountered it, I don't know how it will affect the link state of other ports. The quirk appears to switch ports to EHCI mode, rather than turn off power. Alex
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