On Thu, Jan 12, 2023 at 10:45:03PM +0000, Limonciello, Mario wrote: > [AMD Official Use Only - General] > > > > > -----Original Message----- > > From: Bjorn Helgaas <helgaas@xxxxxxxxxx> > > Sent: Thursday, January 12, 2023 16:41 > > To: Limonciello, Mario <Mario.Limonciello@xxxxxxx> > > Cc: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx>; linux-pci@xxxxxxxxxxxxxxx; Rafael J. > > Wysocki <rafael@xxxxxxxxxx>; Len Brown <lenb@xxxxxxxxxx>; Bjorn Helgaas > > <bhelgaas@xxxxxxxxxx>; Mika Westerberg > > <mika.westerberg@xxxxxxxxxxxxxxx>; Mehta, Sanju <Sanju.Mehta@xxxxxxx>; > > Lukas Wunner <lukas@xxxxxxxxx>; Rafael J . Wysocki > > <rafael.j.wysocki@xxxxxxxxx>; linux-acpi@xxxxxxxxxxxxxxx; linux- > > kernel@xxxxxxxxxxxxxxx; Linux PM <linux-pm@xxxxxxxxxxxxxxx> > > Subject: Re: [PATCH v4] PCI / ACPI: PM: Take _S0W of the target bridge into > > account in acpi_pci_bridge_d3(() > > > > On Thu, Jan 12, 2023 at 10:09:21PM +0000, Limonciello, Mario wrote: > > > > -----Original Message----- > > > > From: Bjorn Helgaas <helgaas@xxxxxxxxxx> > > > > Sent: Thursday, January 12, 2023 16:02 > > > > To: Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> > > > > Cc: linux-pci@xxxxxxxxxxxxxxx; Limonciello, Mario > > > > <Mario.Limonciello@xxxxxxx>; Rafael J. Wysocki <rafael@xxxxxxxxxx>; > > Len > > > > Brown <lenb@xxxxxxxxxx>; Bjorn Helgaas <bhelgaas@xxxxxxxxxx>; Mika > > > > Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>; Mehta, Sanju > > > > <Sanju.Mehta@xxxxxxx>; Lukas Wunner <lukas@xxxxxxxxx>; Rafael J . > > > > Wysocki <rafael.j.wysocki@xxxxxxxxx>; linux-acpi@xxxxxxxxxxxxxxx; linux- > > > > kernel@xxxxxxxxxxxxxxx; Linux PM <linux-pm@xxxxxxxxxxxxxxx> > > > > Subject: Re: [PATCH v4] PCI / ACPI: PM: Take _S0W of the target bridge into > > > > account in acpi_pci_bridge_d3(() > > > > > > > > On Thu, Jan 12, 2023 at 09:51:24PM +0100, Rafael J. Wysocki wrote: > > > > > From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > > > > > > > > > It is generally questionable to allow a PCI bridge to go into D3 if > > > > > it has _S0W returning D2 or a shallower power state, so modify > > > > > acpi_pci_bridge_d3(() to always take the return value of _S0W for the > > > > > target bridge into accout. That is, make it return 'false' if _S0W > > > > > returns D2 or a shallower power state for the target bridge regardless > > > > > of its ancestor PCIe Root Port properties. Of course, this also causes > > > > > 'false' to be returned if the PCIe Root Port itself is the target and > > > > > its _S0W returns D2 or a shallower power state. > > > > > > > > > > However, still allow bridges without _S0W that are power-manageable via > > > > > ACPI to enter D3 to retain the current code behavior in that case. > > > > > > > > > > Link: https://lore.kernel.org/linux-pci/20221031223356.32570-1- > > > > mario.limonciello@xxxxxxx/ > > > > > Reported-by: Mario Limonciello <mario.limonciello@xxxxxxx> > > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx> > > > > > > > > Applied to pci/pm for v6.3, thanks! > > > > > > > > It'd be great if we could include a short description of the problems > > > > users might see. I think the original problem was that on some AMD > > > > systems we put a USB4 router in D3 when it should remain in D0. And I > > > > assume this means something doesn't wake up when it should? Or maybe > > > > we miss a hotplug event? > > > > > > > > If somebody has an example or some text, I'll add it to the commit > > > > log. > > > > > > Here's a blurb for what happens on AMD side: > > > > > > When the platform is configured to not allow the PCIe port used for > > > tunneling to wakeup from D3 it will runtime suspend into D0 and the > > > USB4 controller which is a consumer will runtime suspend into D3. > > > > > > This inconsistency leads to failures to initialize PCIe tunnels for > > > USB4 devices. > > > > And what is J. Random User going to see? DisplayPort not working > > ever? It works to begin with, but not after a suspend? Devices in a > > dock not being able to wake the system? > > > > I don't really know what "PCIe tunnels for USB4 devices not being > > initialized" means for me. I want to know what a problem report from > > a non-expert user might look like. > > DP tunnels aren't affected, so monitors should still work. > > In terms of what doesn't work it depends on the architecture of the > the connected device. Here's some concrete up-leveled examples: > > USB4 docks contain that a PCIe network adapter and that adapter won't > work when the dock is plugged in after the system boot. > > USB4 docks that contain a USB network adapter should work properly, > but downstream USB4 or TBT3 devices connected to that USB4 dock will > not work when the device or dock is plugged in after the system boots. > > TBT3 storage devices connected after the system has booted will not work. Thanks, this is exactly the sort of thing I was looking for. Since they all mention "connected after boot," I assume the issue with the current code is that a hotplug notification is being missed because a bridge is in D3. If the devices are present and enumerated at boot, there's no issue with suspend/resume, right? What do you think of the following possible text? I don't want to be overly specific because I don't think it's practical to list every scenario. We just need a hook to make people think "Hmm, I'm seeing a dock issue; maybe this is the fix." This fixes problems where a hotplug notification is missed because a bridge is in D3. That means hot-added devices such as USB4 docks (and the devices they contain) and Thunderbolt 3 devices may not work.
