| Message ID | 3219454.74lMxhSOWB@kreacher |
|---|---|
| State | New |
| Headers | show |
| Series | PCI: PM: Do not read power state in pci_enable_device_flags() | expand |
On Tue, Mar 16, 2021 at 4:52 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > It should not be necessary to update the current_state field of > struct pci_dev in pci_enable_device_flags() before calling > do_pci_enable_device() for the device, because none of the > code between that point and the pci_set_power_state() call in > do_pci_enable_device() invoked later depends on it. > > Moreover, doing that is actively harmful in some cases. For example, > if the given PCI device depends on an ACPI power resource whose _STA > method initially returns 0 ("off"), but the config space of the PCI > device is accessible and the power state retrieved from the > PCI_PM_CTRL register is D0, the current_state field in the struct > pci_dev representing that device will get out of sync with the > power.state of its ACPI companion object and that will lead to > power management issues going forward. > > To avoid such issues it is better to leave the current_state value > as is until it is changed to PCI_D0 by do_pci_enable_device() as > appropriate. However, the power state of the device is not changed > to PCI_D0 if it is already enabled when pci_enable_device_flags() > gets called for it, so update its current_state in that case, but > use pci_update_current_state() covering platform PM too for that. > > Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/ > Reported-by: Maximilian Luz <luzmaximilian@gmail.com> > Tested-by: Maximilian Luz <luzmaximilian@gmail.com> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Bjorn, can I take this, or do you want to take care of it yourself? > --- > > Max, I've added a T-by from you even though the patch is slightly different > from what you have tested, but the difference shouldn't matter for your case. > > --- > drivers/pci/pci.c | 16 +++------------- > 1 file changed, 3 insertions(+), 13 deletions(-) > > Index: linux-pm/drivers/pci/pci.c > =================================================================== > --- linux-pm.orig/drivers/pci/pci.c > +++ linux-pm/drivers/pci/pci.c > @@ -1870,20 +1870,10 @@ static int pci_enable_device_flags(struc > int err; > int i, bars = 0; > > - /* > - * Power state could be unknown at this point, either due to a fresh > - * boot or a device removal call. So get the current power state > - * so that things like MSI message writing will behave as expected > - * (e.g. if the device really is in D0 at enable time). > - */ > - if (dev->pm_cap) { > - u16 pmcsr; > - pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); > - dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); > - } > - > - if (atomic_inc_return(&dev->enable_cnt) > 1) > + if (atomic_inc_return(&dev->enable_cnt) > 1) { > + pci_update_current_state(dev, dev->current_state); > return 0; /* already enabled */ > + } > > bridge = pci_upstream_bridge(dev); > if (bridge) > > >
On Mon, Mar 22, 2021 at 3:32 PM Rafael J. Wysocki <rafael@kernel.org> wrote: > > On Tue, Mar 16, 2021 at 4:52 PM Rafael J. Wysocki <rjw@rjwysocki.net> wrote: > > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > It should not be necessary to update the current_state field of > > struct pci_dev in pci_enable_device_flags() before calling > > do_pci_enable_device() for the device, because none of the > > code between that point and the pci_set_power_state() call in > > do_pci_enable_device() invoked later depends on it. > > > > Moreover, doing that is actively harmful in some cases. For example, > > if the given PCI device depends on an ACPI power resource whose _STA > > method initially returns 0 ("off"), but the config space of the PCI > > device is accessible and the power state retrieved from the > > PCI_PM_CTRL register is D0, the current_state field in the struct > > pci_dev representing that device will get out of sync with the > > power.state of its ACPI companion object and that will lead to > > power management issues going forward. > > > > To avoid such issues it is better to leave the current_state value > > as is until it is changed to PCI_D0 by do_pci_enable_device() as > > appropriate. However, the power state of the device is not changed > > to PCI_D0 if it is already enabled when pci_enable_device_flags() > > gets called for it, so update its current_state in that case, but > > use pci_update_current_state() covering platform PM too for that. > > > > Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/ > > Reported-by: Maximilian Luz <luzmaximilian@gmail.com> > > Tested-by: Maximilian Luz <luzmaximilian@gmail.com> > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > Bjorn, can I take this, or do you want to take care of it yourself? I'm taking the silence as consent, so the patch has been applied as 5.13 material with the R-by from Mika. > > --- > > > > Max, I've added a T-by from you even though the patch is slightly different > > from what you have tested, but the difference shouldn't matter for your case. > > > > --- > > drivers/pci/pci.c | 16 +++------------- > > 1 file changed, 3 insertions(+), 13 deletions(-) > > > > Index: linux-pm/drivers/pci/pci.c > > =================================================================== > > --- linux-pm.orig/drivers/pci/pci.c > > +++ linux-pm/drivers/pci/pci.c > > @@ -1870,20 +1870,10 @@ static int pci_enable_device_flags(struc > > int err; > > int i, bars = 0; > > > > - /* > > - * Power state could be unknown at this point, either due to a fresh > > - * boot or a device removal call. So get the current power state > > - * so that things like MSI message writing will behave as expected > > - * (e.g. if the device really is in D0 at enable time). > > - */ > > - if (dev->pm_cap) { > > - u16 pmcsr; > > - pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); > > - dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); > > - } > > - > > - if (atomic_inc_return(&dev->enable_cnt) > 1) > > + if (atomic_inc_return(&dev->enable_cnt) > 1) { > > + pci_update_current_state(dev, dev->current_state); > > return 0; /* already enabled */ > > + } > > > > bridge = pci_upstream_bridge(dev); > > if (bridge) > > > > > >
Hi, On Tue, Mar 16, 2021 at 04:51:40PM +0100, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > It should not be necessary to update the current_state field of > struct pci_dev in pci_enable_device_flags() before calling > do_pci_enable_device() for the device, because none of the > code between that point and the pci_set_power_state() call in > do_pci_enable_device() invoked later depends on it. > > Moreover, doing that is actively harmful in some cases. For example, > if the given PCI device depends on an ACPI power resource whose _STA > method initially returns 0 ("off"), but the config space of the PCI > device is accessible and the power state retrieved from the > PCI_PM_CTRL register is D0, the current_state field in the struct > pci_dev representing that device will get out of sync with the > power.state of its ACPI companion object and that will lead to > power management issues going forward. > > To avoid such issues it is better to leave the current_state value > as is until it is changed to PCI_D0 by do_pci_enable_device() as > appropriate. However, the power state of the device is not changed > to PCI_D0 if it is already enabled when pci_enable_device_flags() > gets called for it, so update its current_state in that case, but > use pci_update_current_state() covering platform PM too for that. > > Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/ > Reported-by: Maximilian Luz <luzmaximilian@gmail.com> > Tested-by: Maximilian Luz <luzmaximilian@gmail.com> > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > > Max, I've added a T-by from you even though the patch is slightly different > from what you have tested, but the difference shouldn't matter for your case. > > --- > drivers/pci/pci.c | 16 +++------------- > 1 file changed, 3 insertions(+), 13 deletions(-) > > Index: linux-pm/drivers/pci/pci.c > =================================================================== > --- linux-pm.orig/drivers/pci/pci.c > +++ linux-pm/drivers/pci/pci.c > @@ -1870,20 +1870,10 @@ static int pci_enable_device_flags(struc > int err; > int i, bars = 0; > > - /* > - * Power state could be unknown at this point, either due to a fresh > - * boot or a device removal call. So get the current power state > - * so that things like MSI message writing will behave as expected > - * (e.g. if the device really is in D0 at enable time). > - */ > - if (dev->pm_cap) { > - u16 pmcsr; > - pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); > - dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); > - } > - > - if (atomic_inc_return(&dev->enable_cnt) > 1) > + if (atomic_inc_return(&dev->enable_cnt) > 1) { > + pci_update_current_state(dev, dev->current_state); > return 0; /* already enabled */ > + } > > bridge = pci_upstream_bridge(dev); > if (bridge) A user in Debian reported that this commit caused an issue, cf. https://bugs.debian.org/990008#10 with the e1000e driver failing to probe the device. It was reported as well to https://bugzilla.kernel.org/show_bug.cgi?id=213481 According to the above and https://bugzilla.kernel.org/show_bug.cgi?id=213481#c2 reverting 4514d991d992 ("PCI: PM: Do not read power state in pci_enable_device_flags()") fixes the issue. Any idea what is going on here? Regards, Salvatore
Index: linux-pm/drivers/pci/pci.c =================================================================== --- linux-pm.orig/drivers/pci/pci.c +++ linux-pm/drivers/pci/pci.c @@ -1870,20 +1870,10 @@ static int pci_enable_device_flags(struc int err; int i, bars = 0; - /* - * Power state could be unknown at this point, either due to a fresh - * boot or a device removal call. So get the current power state - * so that things like MSI message writing will behave as expected - * (e.g. if the device really is in D0 at enable time). - */ - if (dev->pm_cap) { - u16 pmcsr; - pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); - dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK); - } - - if (atomic_inc_return(&dev->enable_cnt) > 1) + if (atomic_inc_return(&dev->enable_cnt) > 1) { + pci_update_current_state(dev, dev->current_state); return 0; /* already enabled */ + } bridge = pci_upstream_bridge(dev); if (bridge)