| Message ID | 13011315.uLZWGnKmhe@kreacher |
|---|---|
| State | New |
| Headers | show |
| Series | PCI/PM: Improvements related to device transitions into D0 | expand |
On Mon, Apr 11, 2022 at 04:25:12PM +0200, Rafael J. Wysocki wrote: > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > There are some issues related to changing power states of PCI > devices, mostly related to carrying out unnecessary actions in some > places, and the code is generally hard to follow. > > 1. pci_power_up() has two callers, pci_set_power_state() and > pci_pm_default_resume_early(). The latter updates the current > power state of the device right after calling pci_power_up() > and it restores the entire config space of the device right > after that, so pci_power_up() itself need not read the > PCI_PM_CTRL register or restore the BARs after programming the > device into D0 in that case. > > 2. It is generally hard to get a clear view of the pci_power_up() > code flow, especially in some corner cases, due to all of the > involved PCI_PM_CTRL register reads and writes occurring in > pci_platform_power_transition() and in pci_raw_set_power_state(), > some of which are redundant. > > 3. The transitions from low-power states to D0 and the other way > around are unnecessarily tangled in pci_raw_set_power_state() > which causes it to use a redundant local variable and makes it > rather hard to follow. > > To address the above shortcomings, make the following changes: > > a. Remove the code handling transitions into D0 Should this be D3? > from pci_raw_set_power_state() and rename it as > pci_set_low_power_state(). > > b. Add the code handling transitions into D0 directly > to pci_power_up() and to a new wrapper function > pci_set_full_power_state() calling it internally that is > only used in pci_set_power_state(). > > c. Make pci_power_up() avoid redundant PCI_PM_CTRL register reads > and make it work in the same way for transitions from any > low-power states (transitions from D1 and D2 are handled > slightly differently before the change). > > d. Put the restoration of the BARs and the PCI_PM_CTRL > register read confirming the power state change into > pci_set_full_power_state() to avoid doing that in > pci_pm_default_resume_early() unnecessarily. > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > --- > > v1 -> v2: > * Do not add a redundant check to pci_set_low_power_state(). > > --- > drivers/pci/pci.c | 154 +++++++++++++++++++++++++++++++++++------------------- > 1 file changed, 101 insertions(+), 53 deletions(-) > > Index: linux-pm/drivers/pci/pci.c > =================================================================== > --- linux-pm.orig/drivers/pci/pci.c > +++ linux-pm/drivers/pci/pci.c > @@ -1068,10 +1068,9 @@ static inline bool platform_pci_bridge_d > } > > /** > - * pci_raw_set_power_state - Use PCI PM registers to set the power state of > - * given PCI device > + * pci_set_low_power_state - Program the given 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. > * > * RETURN VALUE: > * -EINVAL if the requested state is invalid. > @@ -1080,10 +1079,9 @@ static inline bool platform_pci_bridge_d > * 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) > @@ -1092,7 +1090,7 @@ static int pci_raw_set_power_state(struc > if (!dev->pm_cap) > return -EIO; > > - if (state < PCI_D0 || state > PCI_D3hot) > + if (state < PCI_D1 || state > PCI_D3hot) > return -EINVAL; > > /* > @@ -1101,8 +1099,7 @@ static int pci_raw_set_power_state(struc > * 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)); > @@ -1122,29 +1119,8 @@ static int pci_raw_set_power_state(struc > 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); > @@ -1153,9 +1129,9 @@ static int pci_raw_set_power_state(struc > * Mandatory power management transition delays; see PCI PM 1.1 > * 5.6.1 table 18 > */ > - if (state == PCI_D3hot || dev->current_state == PCI_D3hot) > + 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); > @@ -1165,22 +1141,6 @@ static int pci_raw_set_power_state(struc > 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); > - > if (dev->bus->self) > pcie_aspm_pm_state_change(dev->bus->self); > > @@ -1312,8 +1272,54 @@ static int pci_dev_wait(struct pci_dev * > */ > int pci_power_up(struct pci_dev *dev) > { > - pci_platform_power_transition(dev, PCI_D0); > - return pci_raw_set_power_state(dev, PCI_D0); > + int ret; > + > + ret = pci_platform_power_transition(dev, PCI_D0); > + if (ret) { Here pci_platform_power_transition() returned an error so we go and read back the PM_CTRL to check in which power state the device is in? Perhaps add a comment here explaining why we need to do this? > + u16 pmcsr; > + > + /* > + * The PCI_PM_CTRL register has not been read above, so read it > + * now and bail out if that fails. > + */ > + pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); > + if (PCI_POSSIBLE_ERROR(pmcsr)) { > + dev->current_state = PCI_D3cold; > + goto fail; > + } > + dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK; > + } else if (dev->current_state == PCI_D3cold) { > + /* > + * Since current_state is PCI_D3cold here, the power state seen > + * by the platform is still D3cold or the PCI_PM_CTRL register > + * read in pci_update_current_state() has failed, so assume the > + * device to be inaccessible. > + */ > + goto fail; > + } > + > + /* There's nothing more to do if current_state is D0 at this point. */ > + if (dev->current_state == PCI_D0) > + return 0; > + > + /* > + * Program the device into PCI_D0 by forcing the entire word to 0 (this > + * doesn't affect PME_Status, disables PME_En, and sets PowerState to 0) > + * and wait for the prescribed amount of time. Assume success. > + */ > + pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, 0); > + > + if (dev->current_state == PCI_D3hot) > + pci_dev_d3_sleep(dev); > + else if (dev->current_state == PCI_D2) > + udelay(PCI_PM_D2_DELAY); > + > + dev->current_state = PCI_D0; > + return 0; > + > +fail: > + pci_err(dev, "Unable to change power state to D0, device inaccessible\n"); > + return -ENODEV; > } > > /** > @@ -1340,6 +1346,48 @@ void pci_bus_set_current_state(struct pc > pci_walk_bus(bus, __pci_dev_set_current_state, &state); > } > Probably good to add some sort of kernel-doc to explain when this function should be used since we have pci_power_up() too (that this one calls). > +static int pci_set_full_power_state(struct pci_dev *dev) > +{ > + pci_power_t old_state = dev->current_state; > + u16 pmcsr; > + int ret; > + > + ret = pci_power_up(dev); > + if (ret) > + return ret; > + > + if (!dev->pm_cap) > + return 0; > + > + 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)); > + } else if (old_state >= PCI_D3hot && !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET)) { > + /* > + * 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. > + */ > + pci_restore_bars(dev); > + } > + > + if (dev->bus->self) > + pcie_aspm_pm_state_change(dev->bus->self); > + > + return 0; > +} > + > /** > * pci_set_power_state - Set the power state of a PCI device > * @dev: PCI device to handle. > @@ -1381,7 +1429,7 @@ int pci_set_power_state(struct pci_dev * > return 0; > > if (state == PCI_D0) > - return pci_power_up(dev); > + return pci_set_full_power_state(dev); > > /* > * This device is quirked not to be put into D3, so don't put it in > @@ -1394,7 +1442,7 @@ int pci_set_power_state(struct pci_dev * > * 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)) > >
On Tue, Apr 12, 2022 at 1:17 PM Mika Westerberg <mika.westerberg@linux.intel.com> wrote: > > On Mon, Apr 11, 2022 at 04:25:12PM +0200, Rafael J. Wysocki wrote: > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > There are some issues related to changing power states of PCI > > devices, mostly related to carrying out unnecessary actions in some > > places, and the code is generally hard to follow. > > > > 1. pci_power_up() has two callers, pci_set_power_state() and > > pci_pm_default_resume_early(). The latter updates the current > > power state of the device right after calling pci_power_up() > > and it restores the entire config space of the device right > > after that, so pci_power_up() itself need not read the > > PCI_PM_CTRL register or restore the BARs after programming the > > device into D0 in that case. > > > > 2. It is generally hard to get a clear view of the pci_power_up() > > code flow, especially in some corner cases, due to all of the > > involved PCI_PM_CTRL register reads and writes occurring in > > pci_platform_power_transition() and in pci_raw_set_power_state(), > > some of which are redundant. > > > > 3. The transitions from low-power states to D0 and the other way > > around are unnecessarily tangled in pci_raw_set_power_state() > > which causes it to use a redundant local variable and makes it > > rather hard to follow. > > > > To address the above shortcomings, make the following changes: > > > > a. Remove the code handling transitions into D0 > > Should this be D3? No. Transitions into D0 will be handled by pci_power_up() directly, so they need not be handled by pci_raw_set_power_state(). > > from pci_raw_set_power_state() and rename it as > > pci_set_low_power_state(). > > > > b. Add the code handling transitions into D0 directly > > to pci_power_up() and to a new wrapper function > > pci_set_full_power_state() calling it internally that is > > only used in pci_set_power_state(). > > > > c. Make pci_power_up() avoid redundant PCI_PM_CTRL register reads > > and make it work in the same way for transitions from any > > low-power states (transitions from D1 and D2 are handled > > slightly differently before the change). > > > > d. Put the restoration of the BARs and the PCI_PM_CTRL > > register read confirming the power state change into > > pci_set_full_power_state() to avoid doing that in > > pci_pm_default_resume_early() unnecessarily. > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > --- > > > > v1 -> v2: > > * Do not add a redundant check to pci_set_low_power_state(). > > > > --- > > drivers/pci/pci.c | 154 +++++++++++++++++++++++++++++++++++------------------- > > 1 file changed, 101 insertions(+), 53 deletions(-) > > > > Index: linux-pm/drivers/pci/pci.c > > =================================================================== > > --- linux-pm.orig/drivers/pci/pci.c > > +++ linux-pm/drivers/pci/pci.c > > @@ -1068,10 +1068,9 @@ static inline bool platform_pci_bridge_d > > } > > > > /** > > - * pci_raw_set_power_state - Use PCI PM registers to set the power state of > > - * given PCI device > > + * pci_set_low_power_state - Program the given 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. > > * > > * RETURN VALUE: > > * -EINVAL if the requested state is invalid. > > @@ -1080,10 +1079,9 @@ static inline bool platform_pci_bridge_d > > * 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) > > @@ -1092,7 +1090,7 @@ static int pci_raw_set_power_state(struc > > if (!dev->pm_cap) > > return -EIO; > > > > - if (state < PCI_D0 || state > PCI_D3hot) > > + if (state < PCI_D1 || state > PCI_D3hot) > > return -EINVAL; > > > > /* > > @@ -1101,8 +1099,7 @@ static int pci_raw_set_power_state(struc > > * 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)); > > @@ -1122,29 +1119,8 @@ static int pci_raw_set_power_state(struc > > 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); > > @@ -1153,9 +1129,9 @@ static int pci_raw_set_power_state(struc > > * Mandatory power management transition delays; see PCI PM 1.1 > > * 5.6.1 table 18 > > */ > > - if (state == PCI_D3hot || dev->current_state == PCI_D3hot) > > + 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); > > @@ -1165,22 +1141,6 @@ static int pci_raw_set_power_state(struc > > 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); > > - > > if (dev->bus->self) > > pcie_aspm_pm_state_change(dev->bus->self); > > > > @@ -1312,8 +1272,54 @@ static int pci_dev_wait(struct pci_dev * > > */ > > int pci_power_up(struct pci_dev *dev) > > { > > - pci_platform_power_transition(dev, PCI_D0); > > - return pci_raw_set_power_state(dev, PCI_D0); > > + int ret; > > + > > + ret = pci_platform_power_transition(dev, PCI_D0); > > + if (ret) { > > Here pci_platform_power_transition() returned an error so we go and read > back the PM_CTRL to check in which power state the device is in? Perhaps > add a comment here explaining why we need to do this? That's the comment below, but I gather it is insufficient as is. Please let me know if rephrasing it this way would help: "Since pci_platform_power_transition() has returned an error, the PCI_PM_CTRL register has not been read by it and the current power state of the device is unknown. Read the PCI_PM_CTRL register now and bail out if that fails." And I've just realized that pm_cap should be checked here, because it is not guaranteed to be set. > > + u16 pmcsr; > > + > > + /* > > + * The PCI_PM_CTRL register has not been read above, so read it > > + * now and bail out if that fails. > > + */ > > + pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); > > + if (PCI_POSSIBLE_ERROR(pmcsr)) { > > + dev->current_state = PCI_D3cold; > > + goto fail; > > + } > > + dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK; > > + } else if (dev->current_state == PCI_D3cold) { > > + /* > > + * Since current_state is PCI_D3cold here, the power state seen > > + * by the platform is still D3cold or the PCI_PM_CTRL register > > + * read in pci_update_current_state() has failed, so assume the > > + * device to be inaccessible. > > + */ > > + goto fail; > > + } > > + > > + /* There's nothing more to do if current_state is D0 at this point. */ > > + if (dev->current_state == PCI_D0) > > + return 0; > > + > > + /* > > + * Program the device into PCI_D0 by forcing the entire word to 0 (this > > + * doesn't affect PME_Status, disables PME_En, and sets PowerState to 0) > > + * and wait for the prescribed amount of time. Assume success. > > + */ > > + pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, 0); > > + > > + if (dev->current_state == PCI_D3hot) > > + pci_dev_d3_sleep(dev); > > + else if (dev->current_state == PCI_D2) > > + udelay(PCI_PM_D2_DELAY); > > + > > + dev->current_state = PCI_D0; > > + return 0; > > + > > +fail: > > + pci_err(dev, "Unable to change power state to D0, device inaccessible\n"); > > + return -ENODEV; > > } > > > > /** > > @@ -1340,6 +1346,48 @@ void pci_bus_set_current_state(struct pc > > pci_walk_bus(bus, __pci_dev_set_current_state, &state); > > } > > > > Probably good to add some sort of kernel-doc to explain when this > function should be used since we have pci_power_up() too (that this one > calls). OK > > +static int pci_set_full_power_state(struct pci_dev *dev) > > +{ > > + pci_power_t old_state = dev->current_state; > > + u16 pmcsr; > > + int ret; > > + > > + ret = pci_power_up(dev); > > + if (ret) > > + return ret; > > + > > + if (!dev->pm_cap) > > + return 0; > > + > > + 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)); > > + } else if (old_state >= PCI_D3hot && !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET)) { > > + /* > > + * 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. > > + */ > > + pci_restore_bars(dev); > > + } > > + > > + if (dev->bus->self) > > + pcie_aspm_pm_state_change(dev->bus->self); > > + > > + return 0; > > +} > > + > > /** > > * pci_set_power_state - Set the power state of a PCI device > > * @dev: PCI device to handle. > > @@ -1381,7 +1429,7 @@ int pci_set_power_state(struct pci_dev * > > return 0; > > > > if (state == PCI_D0) > > - return pci_power_up(dev); > > + return pci_set_full_power_state(dev); > > > > /* > > * This device is quirked not to be put into D3, so don't put it in > > @@ -1394,7 +1442,7 @@ int pci_set_power_state(struct pci_dev * > > * 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)) > > > >
Hi, On Tue, Apr 12, 2022 at 01:31:57PM +0200, Rafael J. Wysocki wrote: > On Tue, Apr 12, 2022 at 1:17 PM Mika Westerberg > <mika.westerberg@linux.intel.com> wrote: > > > > On Mon, Apr 11, 2022 at 04:25:12PM +0200, Rafael J. Wysocki wrote: > > > From: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > > > > There are some issues related to changing power states of PCI > > > devices, mostly related to carrying out unnecessary actions in some > > > places, and the code is generally hard to follow. > > > > > > 1. pci_power_up() has two callers, pci_set_power_state() and > > > pci_pm_default_resume_early(). The latter updates the current > > > power state of the device right after calling pci_power_up() > > > and it restores the entire config space of the device right > > > after that, so pci_power_up() itself need not read the > > > PCI_PM_CTRL register or restore the BARs after programming the > > > device into D0 in that case. > > > > > > 2. It is generally hard to get a clear view of the pci_power_up() > > > code flow, especially in some corner cases, due to all of the > > > involved PCI_PM_CTRL register reads and writes occurring in > > > pci_platform_power_transition() and in pci_raw_set_power_state(), > > > some of which are redundant. > > > > > > 3. The transitions from low-power states to D0 and the other way > > > around are unnecessarily tangled in pci_raw_set_power_state() > > > which causes it to use a redundant local variable and makes it > > > rather hard to follow. > > > > > > To address the above shortcomings, make the following changes: > > > > > > a. Remove the code handling transitions into D0 > > > > Should this be D3? > > No. Transitions into D0 will be handled by pci_power_up() directly, > so they need not be handled by pci_raw_set_power_state(). OK. > > > from pci_raw_set_power_state() and rename it as > > > pci_set_low_power_state(). > > > > > > b. Add the code handling transitions into D0 directly > > > to pci_power_up() and to a new wrapper function > > > pci_set_full_power_state() calling it internally that is > > > only used in pci_set_power_state(). > > > > > > c. Make pci_power_up() avoid redundant PCI_PM_CTRL register reads > > > and make it work in the same way for transitions from any > > > low-power states (transitions from D1 and D2 are handled > > > slightly differently before the change). > > > > > > d. Put the restoration of the BARs and the PCI_PM_CTRL > > > register read confirming the power state change into > > > pci_set_full_power_state() to avoid doing that in > > > pci_pm_default_resume_early() unnecessarily. > > > > > > Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> > > > --- > > > > > > v1 -> v2: > > > * Do not add a redundant check to pci_set_low_power_state(). > > > > > > --- > > > drivers/pci/pci.c | 154 +++++++++++++++++++++++++++++++++++------------------- > > > 1 file changed, 101 insertions(+), 53 deletions(-) > > > > > > Index: linux-pm/drivers/pci/pci.c > > > =================================================================== > > > --- linux-pm.orig/drivers/pci/pci.c > > > +++ linux-pm/drivers/pci/pci.c > > > @@ -1068,10 +1068,9 @@ static inline bool platform_pci_bridge_d > > > } > > > > > > /** > > > - * pci_raw_set_power_state - Use PCI PM registers to set the power state of > > > - * given PCI device > > > + * pci_set_low_power_state - Program the given 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. > > > * > > > * RETURN VALUE: > > > * -EINVAL if the requested state is invalid. > > > @@ -1080,10 +1079,9 @@ static inline bool platform_pci_bridge_d > > > * 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) > > > @@ -1092,7 +1090,7 @@ static int pci_raw_set_power_state(struc > > > if (!dev->pm_cap) > > > return -EIO; > > > > > > - if (state < PCI_D0 || state > PCI_D3hot) > > > + if (state < PCI_D1 || state > PCI_D3hot) > > > return -EINVAL; > > > > > > /* > > > @@ -1101,8 +1099,7 @@ static int pci_raw_set_power_state(struc > > > * 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)); > > > @@ -1122,29 +1119,8 @@ static int pci_raw_set_power_state(struc > > > 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); > > > @@ -1153,9 +1129,9 @@ static int pci_raw_set_power_state(struc > > > * Mandatory power management transition delays; see PCI PM 1.1 > > > * 5.6.1 table 18 > > > */ > > > - if (state == PCI_D3hot || dev->current_state == PCI_D3hot) > > > + 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); > > > @@ -1165,22 +1141,6 @@ static int pci_raw_set_power_state(struc > > > 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); > > > - > > > if (dev->bus->self) > > > pcie_aspm_pm_state_change(dev->bus->self); > > > > > > @@ -1312,8 +1272,54 @@ static int pci_dev_wait(struct pci_dev * > > > */ > > > int pci_power_up(struct pci_dev *dev) > > > { > > > - pci_platform_power_transition(dev, PCI_D0); > > > - return pci_raw_set_power_state(dev, PCI_D0); > > > + int ret; > > > + > > > + ret = pci_platform_power_transition(dev, PCI_D0); > > > + if (ret) { > > > > Here pci_platform_power_transition() returned an error so we go and read > > back the PM_CTRL to check in which power state the device is in? Perhaps > > add a comment here explaining why we need to do this? > > That's the comment below, but I gather it is insufficient as is. > Please let me know if rephrasing it this way would help: > > "Since pci_platform_power_transition() has returned an error, the > PCI_PM_CTRL register has not been read by it and the current power > state of the device is unknown. Read the PCI_PM_CTRL register now and > bail out if that fails." Yes, that's better, thanks! > And I've just realized that pm_cap should be checked here, because it > is not guaranteed to be set. Good point.
Index: linux-pm/drivers/pci/pci.c =================================================================== --- linux-pm.orig/drivers/pci/pci.c +++ linux-pm/drivers/pci/pci.c @@ -1068,10 +1068,9 @@ static inline bool platform_pci_bridge_d } /** - * pci_raw_set_power_state - Use PCI PM registers to set the power state of - * given PCI device + * pci_set_low_power_state - Program the given 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. * * RETURN VALUE: * -EINVAL if the requested state is invalid. @@ -1080,10 +1079,9 @@ static inline bool platform_pci_bridge_d * 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) @@ -1092,7 +1090,7 @@ static int pci_raw_set_power_state(struc if (!dev->pm_cap) return -EIO; - if (state < PCI_D0 || state > PCI_D3hot) + if (state < PCI_D1 || state > PCI_D3hot) return -EINVAL; /* @@ -1101,8 +1099,7 @@ static int pci_raw_set_power_state(struc * 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)); @@ -1122,29 +1119,8 @@ static int pci_raw_set_power_state(struc 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); @@ -1153,9 +1129,9 @@ static int pci_raw_set_power_state(struc * Mandatory power management transition delays; see PCI PM 1.1 * 5.6.1 table 18 */ - if (state == PCI_D3hot || dev->current_state == PCI_D3hot) + 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); @@ -1165,22 +1141,6 @@ static int pci_raw_set_power_state(struc 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); - if (dev->bus->self) pcie_aspm_pm_state_change(dev->bus->self); @@ -1312,8 +1272,54 @@ static int pci_dev_wait(struct pci_dev * */ int pci_power_up(struct pci_dev *dev) { - pci_platform_power_transition(dev, PCI_D0); - return pci_raw_set_power_state(dev, PCI_D0); + int ret; + + ret = pci_platform_power_transition(dev, PCI_D0); + if (ret) { + u16 pmcsr; + + /* + * The PCI_PM_CTRL register has not been read above, so read it + * now and bail out if that fails. + */ + pci_read_config_word(dev, dev->pm_cap + PCI_PM_CTRL, &pmcsr); + if (PCI_POSSIBLE_ERROR(pmcsr)) { + dev->current_state = PCI_D3cold; + goto fail; + } + dev->current_state = pmcsr & PCI_PM_CTRL_STATE_MASK; + } else if (dev->current_state == PCI_D3cold) { + /* + * Since current_state is PCI_D3cold here, the power state seen + * by the platform is still D3cold or the PCI_PM_CTRL register + * read in pci_update_current_state() has failed, so assume the + * device to be inaccessible. + */ + goto fail; + } + + /* There's nothing more to do if current_state is D0 at this point. */ + if (dev->current_state == PCI_D0) + return 0; + + /* + * Program the device into PCI_D0 by forcing the entire word to 0 (this + * doesn't affect PME_Status, disables PME_En, and sets PowerState to 0) + * and wait for the prescribed amount of time. Assume success. + */ + pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, 0); + + if (dev->current_state == PCI_D3hot) + pci_dev_d3_sleep(dev); + else if (dev->current_state == PCI_D2) + udelay(PCI_PM_D2_DELAY); + + dev->current_state = PCI_D0; + return 0; + +fail: + pci_err(dev, "Unable to change power state to D0, device inaccessible\n"); + return -ENODEV; } /** @@ -1340,6 +1346,48 @@ void pci_bus_set_current_state(struct pc pci_walk_bus(bus, __pci_dev_set_current_state, &state); } +static int pci_set_full_power_state(struct pci_dev *dev) +{ + pci_power_t old_state = dev->current_state; + u16 pmcsr; + int ret; + + ret = pci_power_up(dev); + if (ret) + return ret; + + if (!dev->pm_cap) + return 0; + + 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)); + } else if (old_state >= PCI_D3hot && !(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET)) { + /* + * 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. + */ + pci_restore_bars(dev); + } + + if (dev->bus->self) + pcie_aspm_pm_state_change(dev->bus->self); + + return 0; +} + /** * pci_set_power_state - Set the power state of a PCI device * @dev: PCI device to handle. @@ -1381,7 +1429,7 @@ int pci_set_power_state(struct pci_dev * return 0; if (state == PCI_D0) - return pci_power_up(dev); + return pci_set_full_power_state(dev); /* * This device is quirked not to be put into D3, so don't put it in @@ -1394,7 +1442,7 @@ int pci_set_power_state(struct pci_dev * * 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))