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PCI/PM: Split pci_raw_set_power_state()
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The transitions from low-power states to D0 and the other way around
are unnecessarily tangled in pci_raw_set_power_state() which makes it
rather hard to follow.

Moreover, the only caller of pci_raw_set_power_state() passing PCI_D0
as its state argument is pci_power_up(), so the code carrying out
transitions into D0 can be put directly into that function.

Accordingly, move the code handling transitions from low-power states
into D0 directly into pci_power_up() and rename the remaining part
of pci_raw_set_power_state() to pci_set_low_power_state(), because
it only handles transitions into low-power state now.

While at it, fix up some white space, update some comments and modify
messages printed by pci_power_up() and pci_set_low_power_state() to
be less confusing (which is the only expected functional impact of
this change).

Link: https://lore.kernel.org/r/13038676.uLZWGnKmhe@kreacher
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
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Rafael J. Wysocki authored and Bjorn Helgaas committed May 5, 2022
1 parent 9c384dd commit 10aa537
Showing 1 changed file with 83 additions and 60 deletions.
143 changes: 83 additions & 60 deletions drivers/pci/pci.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1068,10 +1068,11 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
}

/**
* pci_raw_set_power_state - Use PCI PM registers to set the power state of
* given PCI device
* pci_set_low_power_state - Put a PCI device into a low-power state.
* @dev: PCI device to handle.
* @state: PCI power state (D0, D1, D2, D3hot) to put the device into.
* @state: PCI power state (D1, D2, D3hot) to put the device into.
*
* Use the device's PCI_PM_CTRL register to put it into a low-power state.
*
* RETURN VALUE:
* -EINVAL if the requested state is invalid.
Expand All @@ -1080,10 +1081,9 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
* 0 if device already is in the requested state.
* 0 if device's power state has been successfully changed.
*/
static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
static int pci_set_low_power_state(struct pci_dev *dev, pci_power_t state)
{
u16 pmcsr;
bool need_restore = false;

/* Check if we're already there */
if (dev->current_state == state)
Expand All @@ -1092,7 +1092,7 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
if (!dev->pm_cap)
return -EIO;

if (state < PCI_D0 || state > PCI_D3hot)
if (state < PCI_D1 || state > PCI_D3hot)
return -EINVAL;

/*
Expand All @@ -1101,8 +1101,7 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)
* we can go from D1 to D3, but we can't go directly from D3 to D1;
* we'd have to go from D3 to D0, then to D1.
*/
if (state != PCI_D0 && dev->current_state <= PCI_D3cold
&& dev->current_state > state) {
if (dev->current_state <= PCI_D3cold && dev->current_state > state) {
pci_err(dev, "invalid power transition (from %s to %s)\n",
pci_power_name(dev->current_state),
pci_power_name(state));
Expand All @@ -1116,70 +1115,30 @@ static int pci_raw_set_power_state(struct pci_dev *dev, pci_power_t state)

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
if (PCI_POSSIBLE_ERROR(pmcsr)) {
pci_err(dev, "can't change power state from %s to %s (config space inaccessible)\n",
pci_err(dev, "Unable to change power state from %s to %s, device inaccessible\n",
pci_power_name(dev->current_state),
pci_power_name(state));
return -EIO;
}

/*
* If we're (effectively) in D3, force entire word to 0.
* This doesn't affect PME_Status, disables PME_En, and
* sets PowerState to 0.
*/
switch (dev->current_state) {
case PCI_D0:
case PCI_D1:
case PCI_D2:
pmcsr &= ~PCI_PM_CTRL_STATE_MASK;
pmcsr |= state;
break;
case PCI_D3hot:
case PCI_D3cold:
case PCI_UNKNOWN: /* Boot-up */
if ((pmcsr & PCI_PM_CTRL_STATE_MASK) == PCI_D3hot
&& !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET))
need_restore = true;
fallthrough; /* force to D0 */
default:
pmcsr = 0;
break;
}
pmcsr &= ~PCI_PM_CTRL_STATE_MASK;
pmcsr |= state;

/* Enter specified state */
pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, pmcsr);

/*
* Mandatory power management transition delays; see PCI PM 1.1
* 5.6.1 table 18
*/
if (state == PCI_D3hot || dev->current_state == PCI_D3hot)
/* Mandatory power management transition delays; see PCI PM 1.2. */
if (state == PCI_D3hot)
pci_dev_d3_sleep(dev);
else if (state == PCI_D2 || dev->current_state == PCI_D2)
else if (state == PCI_D2)
udelay(PCI_PM_D2_DELAY);

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
dev->current_state = (pmcsr & PCI_PM_CTRL_STATE_MASK);
dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK;
if (dev->current_state != state)
pci_info_ratelimited(dev, "refused to change power state from %s to %s\n",
pci_power_name(dev->current_state),
pci_power_name(state));

/*
* According to section 5.4.1 of the "PCI BUS POWER MANAGEMENT
* INTERFACE SPECIFICATION, REV. 1.2", a device transitioning
* from D3hot to D0 _may_ perform an internal reset, thereby
* going to "D0 Uninitialized" rather than "D0 Initialized".
* For example, at least some versions of the 3c905B and the
* 3c556B exhibit this behaviour.
*
* At least some laptop BIOSen (e.g. the Thinkpad T21) leave
* devices in a D3hot state at boot. Consequently, we need to
* restore at least the BARs so that the device will be
* accessible to its driver.
*/
if (need_restore)
pci_restore_bars(dev);
pci_info_ratelimited(dev, "Refused to change power state from %s to %s\n",
pci_power_name(dev->current_state),
pci_power_name(state));

if (dev->bus->self)
pcie_aspm_pm_state_change(dev->bus->self);
Expand Down Expand Up @@ -1312,8 +1271,72 @@ static int pci_dev_wait(struct pci_dev *dev, char *reset_type, int timeout)
*/
int pci_power_up(struct pci_dev *dev)
{
bool need_restore = false;
u16 pmcsr;

pci_platform_power_transition(dev, PCI_D0);
return pci_raw_set_power_state(dev, PCI_D0);

if (dev->current_state == PCI_D0)
return 0;

if (!dev->pm_cap)
return -EIO;

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
if (PCI_POSSIBLE_ERROR(pmcsr)) {
pci_err(dev, "Unable to change power state from %s to D0, device inaccessible\n",
pci_power_name(dev->current_state));
return -EIO;
}

/*
* If we're (effectively) in D3, force entire word to 0. This doesn't
* affect PME_Status, disables PME_En, and sets PowerState to 0.
*/
if (dev->current_state >= PCI_D3hot) {
if ((pmcsr & PCI_PM_CTRL_STATE_MASK) == PCI_D3hot &&
!(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET))
need_restore = true;

pmcsr = 0;
} else {
pmcsr &= ~PCI_PM_CTRL_STATE_MASK;
}

pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, pmcsr);

/* Mandatory transition delays; see PCI PM 1.2. */
if (dev->current_state == PCI_D3hot)
pci_dev_d3_sleep(dev);
else if (dev->current_state == PCI_D2)
udelay(PCI_PM_D2_DELAY);

pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr);
dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK;
if (dev->current_state != PCI_D0)
pci_info_ratelimited(dev, "Refused to change power state from %s to D0\n",
pci_power_name(dev->current_state));

/*
* According to section 5.4.1 of the "PCI BUS POWER MANAGEMENT
* INTERFACE SPECIFICATION, REV. 1.2", a device transitioning
* from D3hot to D0 _may_ perform an internal reset, thereby
* going to "D0 Uninitialized" rather than "D0 Initialized".
* For example, at least some versions of the 3c905B and the
* 3c556B exhibit this behaviour.
*
* At least some laptop BIOSen (e.g. the Thinkpad T21) leave
* devices in a D3hot state at boot. Consequently, we need to
* restore at least the BARs so that the device will be
* accessible to its driver.
*/
if (need_restore)
pci_restore_bars(dev);

if (dev->bus->self)
pcie_aspm_pm_state_change(dev->bus->self);

return 0;
}

/**
Expand Down Expand Up @@ -1394,7 +1417,7 @@ int pci_set_power_state(struct pci_dev *dev, pci_power_t state)
* To put device in D3cold, we put device into D3hot in native
* way, then put device into D3cold with platform ops
*/
error = pci_raw_set_power_state(dev, state > PCI_D3hot ?
error = pci_set_low_power_state(dev, state > PCI_D3hot ?
PCI_D3hot : state);

if (pci_platform_power_transition(dev, state))
Expand Down

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