| Message ID | 20200303132852.13184-5-stanspas@amazon.com |
|---|---|
| State | New |
| Headers | show |
| Series | Improve PCI device post-reset readiness polling | expand |
On Tue, Mar 3, 2020 at 2:30 PM Stanislav Spassov <stanspas@amazon.com> wrote: > > From: Stanislav Spassov <stanspas@amazon.de> > > Both specifications that document mechanisms for overriding the > D3hot->D0 waiting time only speak of this specific direction. > Nothing is mentioned about the opposite (D*->D3hot) except for > the default value of 10ms in PCI Express Base Specification > r5.0 (May 22, 2019), Section 5.9 "State Transition Recovery Time > Requirements". Unless you have a specific example of a system on which the current code doesn't work (and which should be mentioned here), I don't think that it is a good idea to make this change. There are systems in which it would make a measurable difference in things like the time it takes to suspend the system. > Signed-off-by: Stanislav Spassov <stanspas@amazon.de> > --- > drivers/pci/pci.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c > index c1a866f733e9..03103bb15b42 100644 > --- a/drivers/pci/pci.c > +++ b/drivers/pci/pci.c > @@ -4589,7 +4589,7 @@ static int pci_pm_reset(struct pci_dev *dev, int probe) > csr &= ~PCI_PM_CTRL_STATE_MASK; > csr |= PCI_D3hot; > pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, csr); > - pci_dev_d3_sleep(dev); > + msleep(PCI_PM_D3_WAIT); > > csr &= ~PCI_PM_CTRL_STATE_MASK; > csr |= PCI_D0; > -- > 2.25.1 > > > > > Amazon Development Center Germany GmbH > Krausenstr. 38 > 10117 Berlin > Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss > Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B > Sitz: Berlin > Ust-ID: DE 289 237 879 > > >
On Tue, 2020-03-03 at 19:57 +0100, Rafael J. Wysocki wrote: > > Both specifications that document mechanisms for overriding the > > D3hot->D0 waiting time only speak of this specific direction. > > Nothing is mentioned about the opposite (D*->D3hot) except for > > the default value of 10ms in PCI Express Base Specification > > r5.0 (May 22, 2019), Section 5.9 "State Transition Recovery Time > > Requirements". > > Unless you have a specific example of a system on which the current > code doesn't work (and which should be mentioned here), I don't think > that it is a good idea to make this change. > I do not have a specific example for a failing system here. The intention is purely to bring the code in line with what the spec says (or in this case: what the spec does not say). > There are systems in which it would make a measurable difference in > things like the time it takes to suspend the system. This patch only affects the D0->D3hot delay within pci_pm_reset(). (I will make this more explicit in the commit title/message.) The PM reset is only ever invoked from __pci_reset_function_locked() and pci_probe_reset_function(). Specifically, pci_set_power_state() is untouched. I am not well versed into the system suspend code, but unless we are resetting the devices there, this patch should not affect system suspend time at all. Amazon Development Center Germany GmbH Krausenstr. 38 10117 Berlin Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B Sitz: Berlin Ust-ID: DE 289 237 879
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c index c1a866f733e9..03103bb15b42 100644 --- a/drivers/pci/pci.c +++ b/drivers/pci/pci.c @@ -4589,7 +4589,7 @@ static int pci_pm_reset(struct pci_dev *dev, int probe) csr &= ~PCI_PM_CTRL_STATE_MASK; csr |= PCI_D3hot; pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, csr); - pci_dev_d3_sleep(dev); + msleep(PCI_PM_D3_WAIT); csr &= ~PCI_PM_CTRL_STATE_MASK; csr |= PCI_D0;