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Wysocki" Cc: Linux PCI , Stefan Gottwald , Mika Westerberg , Linux PM , LKML Subject: Re: [PATCH] PCI: PM: Quirk bridge D3 on Elo i2 Message-ID: <20220331215716.GA27368@bhelgaas> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <11980172.O9o76ZdvQC@kreacher> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Rafael, On Thu, Mar 31, 2022 at 07:38:51PM +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki > > If one of the PCIe root ports on Elo i2 is put into D3cold and then > back into D0, the downstream device becomes permanently inaccessible, > so add a bridge D3 DMI quirk for that system. > > This was exposed by commit 14858dcc3b35 ("PCI: Use > pci_update_current_state() in pci_enable_device_flags()"), but before > that commit the root port in question had never been put into D3cold > for real due to a mismatch between its power state retrieved from the > PCI_PM_CTRL register (which was accessible even though the platform > firmware indicated that the port was in D3cold) and the state of an > ACPI power resource involved in its power management. In the bug report you suspect a firmware issue. Any idea what that might be? It looks like a Gemini Lake Root Port, so I wouldn't think it would be a hardware issue. Weird how things come in clumps. Was just looking at Mario's patch, which also has to do with bridges and D3. Do we need a Fixes line? E.g., Fixes: 14858dcc3b35 ("PCI: Use pci_update_current_state() in pci_enable_device_flags()") > BugLink: https://bugzilla.kernel.org/show_bug.cgi?id=215715 > Reported-by: Stefan Gottwald > Signed-off-by: Rafael J. Wysocki > --- > drivers/pci/pci.c | 10 ++++++++++ > 1 file changed, 10 insertions(+) > > Index: linux-pm/drivers/pci/pci.c > =================================================================== > --- linux-pm.orig/drivers/pci/pci.c > +++ linux-pm/drivers/pci/pci.c > @@ -2920,6 +2920,16 @@ static const struct dmi_system_id bridge > DMI_MATCH(DMI_BOARD_VENDOR, "Gigabyte Technology Co., Ltd."), > DMI_MATCH(DMI_BOARD_NAME, "X299 DESIGNARE EX-CF"), > }, > + /* > + * Downstream device is not accessible after putting a root port > + * into D3cold and back into D0 on Elo i2. > + */ > + .ident = "Elo i2", > + .matches = { > + DMI_MATCH(DMI_SYS_VENDOR, "Elo Touch Solutions"), > + DMI_MATCH(DMI_PRODUCT_NAME, "Elo i2"), > + DMI_MATCH(DMI_PRODUCT_VERSION, "RevB"), > + }, Is this bridge_d3_blacklist[] similar to the PCI_DEV_FLAGS_NO_D3 bit? Could they be folded together? We have a lot of bits that seem similar but maybe not exactly the same (dev->bridge_d3, dev->no_d3cold, dev->d3cold_allowed, dev->runtime_d3cold, PCI_DEV_FLAGS_NO_D3, pci_bridge_d3_force, etc.) Ugh. bridge_d3_blacklist[] itself was added by 85b0cae89d52 ("PCI: Blacklist power management of Gigabyte X299 DESIGNARE EX PCIe ports"), which honestly looks kind of random, i.e., it doesn't seem to be working around a hardware or even a firmware defect. Apparently the X299 issue is that 00:1c.4 is connected to a Thunderbolt controller, and the BIOS keeps the Thunderbolt controller powered off unless something is attached to it? At least, 00:1c.4 leads to bus 05, and in the dmesg log attached to [1] shows no devices on bus 05. It also says the platform doesn't support PCIe native hotplug, which matches what Mika said about it using ACPI hotplug. If a system is using ACPI hotplug, it seems like maybe *that* should prevent us from putting things in D3cold? How can we know whether ACPI hotplug depends on a certain power state? Bjorn [1] https://bugzilla.kernel.org/show_bug.cgi?id=202031 > }, > #endif > { } > > >