On Wednesday, 7 of May 2008, Rafael J. Wysocki wrote:
> On Wednesday, 7 of May 2008, Alan Stern wrote:
> > On Wed, 7 May 2008, Rafael J. Wysocki wrote:
> >
> > > On Wednesday, 7 of May 2008, Pavel Machek wrote:
> > > > Hi!
> > > >
> > > > > From: Rafael J. Wysocki <rjw@xxxxxxx>
> > > > >
> > > > > The new suspend and hibernation callbacks introduced with
> > > > > 'struct pm_ops' and 'struct pm_ext_ops' do not take a
> > > > > pm_message_t argument, so the drivers using them will not be able
> > > > > to use pci_choose_state() in its present form. For this reason,
> > > > > introduce the new function pci_preferred_state() playing the role
> > > > > of pci_choose_state(), but taking only a pointer to the device
> > > > > object.
> > > > >
> > > > > Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
> > > > > ---
> > > > > drivers/pci/pci.c | 33 ++++++++++++++++++++++++++++++++-
> > > > > include/linux/pci.h | 1 +
> > > > > include/linux/pm.h | 10 ++++++++++
> > > > > 3 files changed, 43 insertions(+), 1 deletion(-)
> > > > >
> > > > > Index: linux-2.6/drivers/pci/pci.c
> > > > > ===================================================================
> > > > > --- linux-2.6.orig/drivers/pci/pci.c
> > > > > +++ linux-2.6/drivers/pci/pci.c
> > > > > @@ -509,7 +509,38 @@ pci_set_power_state(struct pci_dev *dev,
> > > > > }
> > > > >
> > > > > pci_power_t (*platform_pci_choose_state)(struct pci_dev *dev);
> > > > > -
> > > > > +
> > > > > +/**
> > > > > + * pci_preferred_state - Choose the preferred power state of a PCI device
> > > > > + * @dev: PCI device to be put into the low power state
> > > > > + * @sp: Information aboutabout what the driver would prefer to do with
> > > > > + * the device if there were no platform-implemeted policy.
> > > > > + *
> > > > > + * Returns PCI power state suitable for given device and given suspend policy.
> > > > > + * The policy, however, is only used if platform_pci_choose_state() fails or is
> > > > > + * not present. Otherwise, it is assumed that platform_pci_choose_state()
> > > > > + * implements the right policy.
> > > > > + */
> > > > > +
> > > > > +pci_power_t pci_preferred_state(struct pci_dev *dev, enum suspend_policy sp)
> > > > > +{
> > > > > + pci_power_t ret;
> > > > > +
> > > > > + if (!pci_find_capability(dev, PCI_CAP_ID_PM))
> > > > > + return PCI_D0;
> > > > > +
> > > > > + ret = (sp == SP_TURN_OFF) ? PCI_D3hot : PCI_D0;
> > > > > + if (platform_pci_choose_state) {
> > > > > + pci_power_t platform_ret = platform_pci_choose_state(dev);
> > > > > +
> > > > > + if (platform_ret != PCI_POWER_ERROR)
> > > > > + ret = platform_ret;
> > > > > + }
> > > > > + return ret;
> > > > > +}
> > > > > +
> > > > > +EXPORT_SYMBOL(pci_preferred_state);
> > > >
> > > > I don't get it. How is driver supposed to use this? How does the
> > > > driver decide between SP_TURN_OFF and SP_TURN_ON?
> > > >
> > > > ...and it seems to be clearer to just inline this in the driver... or
> > > > pass PCI_D3hot/PCI_D0 to it, instead of inventing yet another
> > > > define...
> > >
> > > I thought about that too. I'd like to know what the other people think,
> > > though.
> >
> > The point of this isn't at all clear.
> >
> > Is this routine meant to be called during a hibernation
> > transition?
>
> Yes, it is.
>
> > Or is it just for suspend?
> >
> > And why would the return value ever be anything other than D3_hot? (Or
> > why would the driver ever want to put a device in a different state?)
>
> In principle, the driver may want to put the device into a state having shorter
> wake up latency than D3_hot.
>
> > AFAICS, the only reason would be because platform_pci_choose_state()
> > suggested something else. In which case there's no need for the
> > "policy" argument.
>
> There is a need in two cases:
> - if platform_pci_choose_state() is not defined (it only is defined for ACPI
> systems at the moment),
> - if platform_pci_choose_state() returns PCI_POWER_ERROR meaning that it cannot
> handle the device.
>
> I agree with Pavel that the driver could pass a "fallback state" as a second
> argument to be used in case the platform cannot provide it with one.
Modified patch follows.
Thanks,
Rafael
---
From: Rafael J. Wysocki <rjw@xxxxxxx>
The new suspend and hibernation callbacks introduced with
'struct pm_ops' and 'struct pm_ext_ops' do not take a
pm_message_t argument, so the drivers using them will not be able
to use pci_choose_state() in its present form. For this reason,
introduce the new function pci_preferred_state() playing the role
of pci_choose_state(), but taking only the pointer to the device
object.
Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
drivers/pci/pci.c | 28 +++++++++++++++++++++++++++-
include/linux/pci.h | 1 +
2 files changed, 28 insertions(+), 1 deletion(-)
Index: linux-2.6/drivers/pci/pci.c
===================================================================
--- linux-2.6.orig/drivers/pci/pci.c
+++ linux-2.6/drivers/pci/pci.c
@@ -509,7 +509,33 @@ pci_set_power_state(struct pci_dev *dev,
}
pci_power_t (*platform_pci_choose_state)(struct pci_dev *dev);
-
+
+/**
+ * pci_preferred_state - Choose the preferred power state of a PCI device
+ * @dev: PCI device to be put into the low power state
+ * @state: State to put the device into if the platform cannot handle it
+ *
+ * Returns PCI power state suitable for given device according to the platform.
+ * However, if platform_pci_choose_state() is not defined or returns
+ * PCI_POWER_ERROR, @state is returned.
+ */
+
+pci_power_t pci_preferred_state(struct pci_dev *dev, pci_power_t state)
+{
+ if (!pci_find_capability(dev, PCI_CAP_ID_PM))
+ return state;
+
+ if (platform_pci_choose_state) {
+ pci_power_t ret = platform_pci_choose_state(dev);
+
+ if (ret != PCI_POWER_ERROR)
+ state = ret;
+ }
+ return state;
+}
+
+EXPORT_SYMBOL(pci_preferred_state);
+
/**
* pci_choose_state - Choose the power state of a PCI device
* @dev: PCI device to be suspended
Index: linux-2.6/include/linux/pci.h
===================================================================
--- linux-2.6.orig/include/linux/pci.h
+++ linux-2.6/include/linux/pci.h
@@ -615,6 +615,7 @@ size_t pci_get_rom_size(void __iomem *ro
int pci_save_state(struct pci_dev *dev);
int pci_restore_state(struct pci_dev *dev);
int pci_set_power_state(struct pci_dev *dev, pci_power_t state);
+pci_power_t pci_preferred_state(struct pci_dev *dev, pci_power_t state);
pci_power_t pci_choose_state(struct pci_dev *dev, pm_message_t state);
int pci_enable_wake(struct pci_dev *dev, pci_power_t state, int enable);
--
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