| Message ID | 151908203999.37696.12678235610905422348.stgit@bhelgaas-glaptop.roam.corp.google.com |
|---|---|
| State | New |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | PCI/PM: Add comments, allow PM of conventional & hotplug bridges | expand |
On Tue, Feb 20, 2018 at 12:14 AM, Bjorn Helgaas <helgaas@kernel.org> wrote: > From: Bjorn Helgaas <bhelgaas@google.com> > > Add details about how we decide whether we can put a PCI bridge in D3. > 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend") added this > support to reduce power consumption on Intel Sunrise Point and Broxton > platforms. > > In some cases we don't use D3 for bridges even when it should work, simply > because it's impractical to test the configuration, or we tripped over some > possible hardware issue on older platforms. Links to discussion of the > PCIe port runtime power management patches, which includes mention of these > issues, are below. > > No functional change. > > Link: v1: https://lkml.kernel.org/r/1456750566-116248-1-git-send-email-mika.westerberg@linux.intel.com > Link: v2: https://lkml.kernel.org/r/1460111790-92836-1-git-send-email-mika.westerberg@linux.intel.com > Link: v3: https://lkml.kernel.org/r/1460628268-16204-1-git-send-email-mika.westerberg@linux.intel.com > Link: v4: https://lkml.kernel.org/r/1461578004-129094-1-git-send-email-mika.westerberg@linux.intel.com > Link: v5: https://lkml.kernel.org/r/1461919919-120102-1-git-send-email-mika.westerberg@linux.intel.com > Link: v6: https://lkml.kernel.org/r/1464855435-32960-1-git-send-email-mika.westerberg@linux.intel.com > Link: https://lkml.kernel.org/r/2858019.9TUCWsDpTB@aspire.rjw.lan > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > drivers/pci/pci.c | 19 ++++++++++++++++++- > 1 file changed, 18 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index f6a4dd10d9b0..75db77cf3f8f 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -2260,6 +2260,13 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) > { > unsigned int year; > > + /* > + * In principle we should be able to put conventional PCI bridges > + * into D3. We only support it for PCIe because (a) we want to > + * save power on new (2015 and newer) SoCs that can enter deep > + * low-power states only if PCIe Root Ports are in D3 and (b) we > + * don't want to risk regressions on older hardware. > + */ > if (!pci_is_pcie(bridge)) > return false; > > @@ -2276,6 +2283,14 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) > * hotplug ports handled by firmware in System Management Mode > * may not be put into D3 by the OS (Thunderbolt on non-Macs). > * For simplicity, disallow in general for now. > + * > + * Per PCIe r4.0, sec 6.7.3.4, if the form factor requires > + * wake support, a hot-plug capable Downstream Port must > + * support generation of a wakeup event on hot-plug events > + * that occur when the system is in a sleep state or the > + * Port is in device state D1, D2, or D3hot. Therefore, it > + * might be possible to use D3 even for hot-plug Ports, but > + * for now we do not. > */ > if (bridge->is_hotplug_bridge) > return false; > @@ -2285,7 +2300,9 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) > > /* > * It should be safe to put PCIe ports from 2015 or newer > - * to D3. > + * to D3. We have vague reports of possible hardware > + * issues when putting older PCIe ports into D3. See > + * changelog. > */ > if (dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL) && > year >= 2015) { >
On Tue, Feb 20, 2018 at 10:31:51AM +0100, Rafael J. Wysocki wrote: > On Tue, Feb 20, 2018 at 12:14 AM, Bjorn Helgaas <helgaas@kernel.org> wrote: > > From: Bjorn Helgaas <bhelgaas@google.com> > > > > Add details about how we decide whether we can put a PCI bridge in D3. > > 9d26d3a8f1b0 ("PCI: Put PCIe ports into D3 during suspend") added this > > support to reduce power consumption on Intel Sunrise Point and Broxton > > platforms. > > > > In some cases we don't use D3 for bridges even when it should work, simply > > because it's impractical to test the configuration, or we tripped over some > > possible hardware issue on older platforms. Links to discussion of the > > PCIe port runtime power management patches, which includes mention of these > > issues, are below. > > > > No functional change. > > > > Link: v1: https://lkml.kernel.org/r/1456750566-116248-1-git-send-email-mika.westerberg@linux.intel.com > > Link: v2: https://lkml.kernel.org/r/1460111790-92836-1-git-send-email-mika.westerberg@linux.intel.com > > Link: v3: https://lkml.kernel.org/r/1460628268-16204-1-git-send-email-mika.westerberg@linux.intel.com > > Link: v4: https://lkml.kernel.org/r/1461578004-129094-1-git-send-email-mika.westerberg@linux.intel.com > > Link: v5: https://lkml.kernel.org/r/1461919919-120102-1-git-send-email-mika.westerberg@linux.intel.com > > Link: v6: https://lkml.kernel.org/r/1464855435-32960-1-git-send-email-mika.westerberg@linux.intel.com > > Link: https://lkml.kernel.org/r/2858019.9TUCWsDpTB@aspire.rjw.lan > > Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> > > Reviewed-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Also Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index f6a4dd10d9b0..75db77cf3f8f 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -2260,6 +2260,13 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) { unsigned int year; + /* + * In principle we should be able to put conventional PCI bridges + * into D3. We only support it for PCIe because (a) we want to + * save power on new (2015 and newer) SoCs that can enter deep + * low-power states only if PCIe Root Ports are in D3 and (b) we + * don't want to risk regressions on older hardware. + */ if (!pci_is_pcie(bridge)) return false; @@ -2276,6 +2283,14 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) * hotplug ports handled by firmware in System Management Mode * may not be put into D3 by the OS (Thunderbolt on non-Macs). * For simplicity, disallow in general for now. + * + * Per PCIe r4.0, sec 6.7.3.4, if the form factor requires + * wake support, a hot-plug capable Downstream Port must + * support generation of a wakeup event on hot-plug events + * that occur when the system is in a sleep state or the + * Port is in device state D1, D2, or D3hot. Therefore, it + * might be possible to use D3 even for hot-plug Ports, but + * for now we do not. */ if (bridge->is_hotplug_bridge) return false; @@ -2285,7 +2300,9 @@ bool pci_bridge_d3_possible(struct pci_dev *bridge) /* * It should be safe to put PCIe ports from 2015 or newer - * to D3. + * to D3. We have vague reports of possible hardware + * issues when putting older PCIe ports into D3. See + * changelog. */ if (dmi_get_date(DMI_BIOS_DATE, &year, NULL, NULL) && year >= 2015) {