| Message ID | 20231213182656.6165-2-mario.limonciello@amd.com (mailing list archive) |
|---|---|
| State | New |
| Delegated to: | Bjorn Helgaas |
| Headers | show |
| Series | Improvements to system power consumption at S5 | expand |
On Wed, Dec 13, 2023 at 7:27 PM Mario Limonciello <mario.limonciello@amd.com> wrote: > > When the system is going to S5 resuming devices is unnecessary at > best and may cause problems for power consumption at S5 at worst. > > Check the target `system_state` in the pci driver shutdown() callback > and skip the runtime resume step if the system is being powered off. > > Cc: mpearson-lenovo@squebb.ca > Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> > --- > drivers/pci/pci-driver.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > index 51ec9e7e784f..5a6f7a786952 100644 > --- a/drivers/pci/pci-driver.c > +++ b/drivers/pci/pci-driver.c > @@ -507,7 +507,9 @@ static void pci_device_shutdown(struct device *dev) > struct pci_dev *pci_dev = to_pci_dev(dev); > struct pci_driver *drv = pci_dev->driver; > > - pm_runtime_resume(dev); > + /* If system will go to S5, don't wake up PCI devices for shutdown */ > + if (system_state != SYSTEM_POWER_OFF) > + pm_runtime_resume(dev); What's the guarantee that the driver's shutdown callback will not access MMIO regions of a runtime-suspended device? > if (drv && drv->shutdown) > drv->shutdown(pci_dev); > --
On 12/13/2023 12:31, Rafael J. Wysocki wrote: > On Wed, Dec 13, 2023 at 7:27 PM Mario Limonciello > <mario.limonciello@amd.com> wrote: >> >> When the system is going to S5 resuming devices is unnecessary at >> best and may cause problems for power consumption at S5 at worst. >> >> Check the target `system_state` in the pci driver shutdown() callback >> and skip the runtime resume step if the system is being powered off. >> >> Cc: mpearson-lenovo@squebb.ca >> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> >> --- >> drivers/pci/pci-driver.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c >> index 51ec9e7e784f..5a6f7a786952 100644 >> --- a/drivers/pci/pci-driver.c >> +++ b/drivers/pci/pci-driver.c >> @@ -507,7 +507,9 @@ static void pci_device_shutdown(struct device *dev) >> struct pci_dev *pci_dev = to_pci_dev(dev); >> struct pci_driver *drv = pci_dev->driver; >> >> - pm_runtime_resume(dev); >> + /* If system will go to S5, don't wake up PCI devices for shutdown */ >> + if (system_state != SYSTEM_POWER_OFF) >> + pm_runtime_resume(dev); > > What's the guarantee that the driver's shutdown callback will not > access MMIO regions of a runtime-suspended device? This is something that may need to be audited. I have an expectation that drivers will runtime resume a device before they try to access it. > >> if (drv && drv->shutdown) >> drv->shutdown(pci_dev); >> --
On Wed, Dec 13, 2023 at 7:33 PM Mario Limonciello <mario.limonciello@amd.com> wrote: > > On 12/13/2023 12:31, Rafael J. Wysocki wrote: > > On Wed, Dec 13, 2023 at 7:27 PM Mario Limonciello > > <mario.limonciello@amd.com> wrote: > >> > >> When the system is going to S5 resuming devices is unnecessary at > >> best and may cause problems for power consumption at S5 at worst. > >> > >> Check the target `system_state` in the pci driver shutdown() callback > >> and skip the runtime resume step if the system is being powered off. > >> > >> Cc: mpearson-lenovo@squebb.ca > >> Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> > >> --- > >> drivers/pci/pci-driver.c | 4 +++- > >> 1 file changed, 3 insertions(+), 1 deletion(-) > >> > >> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c > >> index 51ec9e7e784f..5a6f7a786952 100644 > >> --- a/drivers/pci/pci-driver.c > >> +++ b/drivers/pci/pci-driver.c > >> @@ -507,7 +507,9 @@ static void pci_device_shutdown(struct device *dev) > >> struct pci_dev *pci_dev = to_pci_dev(dev); > >> struct pci_driver *drv = pci_dev->driver; > >> > >> - pm_runtime_resume(dev); > >> + /* If system will go to S5, don't wake up PCI devices for shutdown */ > >> + if (system_state != SYSTEM_POWER_OFF) > >> + pm_runtime_resume(dev); > > > > What's the guarantee that the driver's shutdown callback will not > > access MMIO regions of a runtime-suspended device? > > This is something that may need to be audited. > > I have an expectation that drivers will runtime resume a device before > they try to access it. But they don't need to do it, because the core does it right now, which is my point.
diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c index 51ec9e7e784f..5a6f7a786952 100644 --- a/drivers/pci/pci-driver.c +++ b/drivers/pci/pci-driver.c @@ -507,7 +507,9 @@ static void pci_device_shutdown(struct device *dev) struct pci_dev *pci_dev = to_pci_dev(dev); struct pci_driver *drv = pci_dev->driver; - pm_runtime_resume(dev); + /* If system will go to S5, don't wake up PCI devices for shutdown */ + if (system_state != SYSTEM_POWER_OFF) + pm_runtime_resume(dev); if (drv && drv->shutdown) drv->shutdown(pci_dev);
When the system is going to S5 resuming devices is unnecessary at best and may cause problems for power consumption at S5 at worst. Check the target `system_state` in the pci driver shutdown() callback and skip the runtime resume step if the system is being powered off. Cc: mpearson-lenovo@squebb.ca Signed-off-by: Mario Limonciello <mario.limonciello@amd.com> --- drivers/pci/pci-driver.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)