| Message ID | 20250401153225.96379-4-anshuman.gupta@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | VRAM Self Refresh | expand |
On Tue, Apr 01, 2025 at 09:02:16PM +0530, Anshuman Gupta wrote: > Adding a notifier to notify all PCIe child devices about the > block main power removal. It is needed because theoretically > multiple PCIe Endpoint devices on same Root Port > can request for AUX power and _DSM method can return with > 80000000h signifies that the hierarchy connected via > the slot cannot support main power removal when in D3Cold. I wish the spec used different language here. "D3cold" *means* "main power is removed" (PCIe r6.0, sec 5.3.1.4.2), so it doesn't make sense to say that "the slot cannot support main power removal when in D3cold". If a device is in D3cold, its main power has been removed by definition. I suppose the spec is trying to say if the driver has called this _DSM with 80000000h, it means the platform must not remove main power from the device while the system is in S0? Is that what you think it means? The 2h return value description says it "indicates that the platform will not remove main power from the slot while the system is in S0," so I guess that must be it. In this series, pci_acpi_aux_power_setup() only supplies a 16-bit aux_pwr_limit value, so the driver cannot *request* that the platform not remove main power. So I guess the only scenario where the _DSM returns 80000000h is when the platform itself or other devices prevent the removal of main power. And the point of the notifier is to tell devices that their main power will never be removed while the system is in S0. Is that right? > This may disrupt functionality of other child device. What sort of disruption could happen? I would think that if the _DSM returns 80000000h, it just means the device will not have main power removed, so it won't see that power state transition. The only "disruption" would be that we're using more power. > Let's notify all PCIe devices requested Aux power resource > and Let PCIe End Point driver handle it in its callback. Wrap to fill 75 columns. s/Adding/Add/ s/Let's notify/Notify/ s/and Let/and let/ s/End Point/Endpoint/ (several places here and below) > Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com> > --- > drivers/pci/pci-acpi.c | 34 +++++++++++++++++++++++++++++++--- > include/linux/pci-acpi.h | 13 +++++++++++++ > 2 files changed, 44 insertions(+), 3 deletions(-) > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > index 04149f037664..d1ca1649e6e8 100644 > --- a/drivers/pci/pci-acpi.c > +++ b/drivers/pci/pci-acpi.c > @@ -1421,6 +1421,32 @@ static void pci_acpi_optimize_delay(struct pci_dev *pdev, > ACPI_FREE(obj); > } > > +static BLOCKING_NOTIFIER_HEAD(pci_acpi_aux_power_notify_list); > + > +/** > + * pci_acpi_register_aux_power_notifier - Register driver notifier > + * @nb: notifier block > + * > + * This function shall be called by PCIe End Point device requested the Aux > + * power resource in order to handle the any scenario gracefully when other > + * child PCIe devices Aux power request returns with No main power removal. > + * PCIe devices which register this notifier shall handle No main power > + * removal scenario accordingly. This would actually be called by the *driver* (not by the device). Reword in imperative mood if possible. > + * > + * Return: Returns 0 on success and errno on failure. > + */ > +int pci_acpi_register_aux_power_notifier(struct notifier_block *nb) > +{ > + return blocking_notifier_chain_register(&pci_acpi_aux_power_notify_list, nb); > +} > +EXPORT_SYMBOL_GPL(pci_acpi_register_aux_power_notifier); > + > +void pci_acpi_unregister_aux_power_notifier(struct notifier_block *nb) > +{ > + blocking_notifier_chain_unregister(&pci_acpi_aux_power_notify_list, nb); > +} > +EXPORT_SYMBOL_GPL(pci_acpi_unregister_aux_power_notifier); > + > /** > * pci_acpi_request_d3cold_aux_power - Request D3cold aux power via ACPI DSM > * @dev: PCI device instance > @@ -1466,17 +1492,19 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power) > result = out_obj->integer.value; > > switch (result) { > - case 0x0: > + case ACPI_AUX_PW_DENIED: Add these constants in the patch that adds the _DSM. Then this patch will be just notifier-related code. > dev_dbg(&dev->dev, "D3cold Aux Power %umW request denied\n", > requested_power); > break; > - case 0x1: > + case ACPI_AUX_PW_GRANTED: > dev_info(&dev->dev, "D3cold Aux Power request granted: %umW\n", > requested_power); > ret = 0; > break; > - case 0x2: > + case ACPI_NO_MAIN_PW_REMOVAL: > dev_info(&dev->dev, "D3cold Aux Power: Main power won't be removed\n"); > + blocking_notifier_call_chain(&pci_acpi_aux_power_notify_list, > + ACPI_NO_MAIN_PW_REMOVAL, dev); > ret = -EBUSY; > break; > default: > diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h > index 4b7373f91a9a..793b979af98b 100644 > --- a/include/linux/pci-acpi.h > +++ b/include/linux/pci-acpi.h > @@ -124,6 +124,10 @@ extern const guid_t pci_acpi_dsm_guid; > #define DSM_PCI_D3COLD_AUX_POWER_LIMIT 0x0A > #define DSM_PCI_PERST_ASSERTION_DELAY 0x0B > > +#define ACPI_AUX_PW_DENIED 0x0 > +#define ACPI_AUX_PW_GRANTED 0x1 > +#define ACPI_NO_MAIN_PW_REMOVAL 0x2 > + > #ifdef CONFIG_PCIE_EDR > void pci_acpi_add_edr_notifier(struct pci_dev *pdev); > void pci_acpi_remove_edr_notifier(struct pci_dev *pdev); > @@ -134,12 +138,21 @@ static inline void pci_acpi_remove_edr_notifier(struct pci_dev *pdev) { } > > int pci_acpi_set_companion_lookup_hook(struct acpi_device *(*func)(struct pci_dev *)); > void pci_acpi_clear_companion_lookup_hook(void); > +int pci_acpi_register_aux_power_notifier(struct notifier_block *nb); > +void pci_acpi_unregister_aux_power_notifier(struct notifier_block *nb); > int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power); > int pci_acpi_add_perst_assertion_delay(struct pci_dev *dev, u32 delay_us); > > #else /* CONFIG_ACPI */ > static inline void acpi_pci_add_bus(struct pci_bus *bus) { } > static inline void acpi_pci_remove_bus(struct pci_bus *bus) { } > +int pci_acpi_register_aux_power_notifier(struct notifier_block *nb) > +{ > + return -EOPNOTSUPP; > +} > + > +void pci_acpi_unregister_aux_power_notifier(struct notifier_block *nb) { } > + > int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power) > { > return -EOPNOTSUPP; > -- > 2.43.0 >
On Tue, Apr 1, 2025 at 10:13 PM Bjorn Helgaas <helgaas@kernel.org> wrote: > > On Tue, Apr 01, 2025 at 09:02:16PM +0530, Anshuman Gupta wrote: > > Adding a notifier to notify all PCIe child devices about the > > block main power removal. It is needed because theoretically > > multiple PCIe Endpoint devices on same Root Port > > can request for AUX power and _DSM method can return with > > 80000000h signifies that the hierarchy connected via > > the slot cannot support main power removal when in D3Cold. > > I wish the spec used different language here. "D3cold" *means* "main > power is removed" (PCIe r6.0, sec 5.3.1.4.2), so it doesn't make sense > to say that "the slot cannot support main power removal when in > D3cold". If a device is in D3cold, its main power has been removed by > definition. > > I suppose the spec is trying to say if the driver has called this _DSM > with 80000000h, it means the platform must not remove main power from > the device while the system is in S0? Is that what you think it > means? > > The 2h return value description says it "indicates that the platform > will not remove main power from the slot while the system is in S0," > so I guess that must be it. > > In this series, pci_acpi_aux_power_setup() only supplies a 16-bit > aux_pwr_limit value, so the driver cannot *request* that the platform > not remove main power. > > So I guess the only scenario where the _DSM returns 80000000h is when > the platform itself or other devices prevent the removal of main > power. And the point of the notifier is to tell devices that their > main power will never be removed while the system is in S0. Is that > right? > > > This may disrupt functionality of other child device. > > What sort of disruption could happen? I would think that if the _DSM > returns 80000000h, it just means the device will not have main power > removed, so it won't see that power state transition. The only > "disruption" would be that we're using more power. > > > Let's notify all PCIe devices requested Aux power resource > > and Let PCIe End Point driver handle it in its callback. > > Wrap to fill 75 columns. > > s/Adding/Add/ > s/Let's notify/Notify/ > s/and Let/and let/ > s/End Point/Endpoint/ (several places here and below) > > > Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com> > > --- > > drivers/pci/pci-acpi.c | 34 +++++++++++++++++++++++++++++++--- > > include/linux/pci-acpi.h | 13 +++++++++++++ > > 2 files changed, 44 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > > index 04149f037664..d1ca1649e6e8 100644 > > --- a/drivers/pci/pci-acpi.c > > +++ b/drivers/pci/pci-acpi.c > > @@ -1421,6 +1421,32 @@ static void pci_acpi_optimize_delay(struct pci_dev *pdev, > > ACPI_FREE(obj); > > } > > > > +static BLOCKING_NOTIFIER_HEAD(pci_acpi_aux_power_notify_list); > > + > > +/** > > + * pci_acpi_register_aux_power_notifier - Register driver notifier > > + * @nb: notifier block > > + * > > + * This function shall be called by PCIe End Point device requested the Aux > > + * power resource in order to handle the any scenario gracefully when other > > + * child PCIe devices Aux power request returns with No main power removal. > > + * PCIe devices which register this notifier shall handle No main power > > + * removal scenario accordingly. > > This would actually be called by the *driver* (not by the device). Apart from this, there seems to be a design issue here because it won't notify every driver that has requested the Aux power, just the ones that have also registered notifiers. So this appears to be an opt-in from getting notifications on Aux power request rejection responses to requests from other drivers requesting Aux power for the same Root Port, but the changelog of the first patch already claimed that the aggregation of requests was not supported. So if only one driver will be allowed to request the Aux power for the given Root Port, why would the notifiers be necessary after all?
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c index 04149f037664..d1ca1649e6e8 100644 --- a/drivers/pci/pci-acpi.c +++ b/drivers/pci/pci-acpi.c @@ -1421,6 +1421,32 @@ static void pci_acpi_optimize_delay(struct pci_dev *pdev, ACPI_FREE(obj); } +static BLOCKING_NOTIFIER_HEAD(pci_acpi_aux_power_notify_list); + +/** + * pci_acpi_register_aux_power_notifier - Register driver notifier + * @nb: notifier block + * + * This function shall be called by PCIe End Point device requested the Aux + * power resource in order to handle the any scenario gracefully when other + * child PCIe devices Aux power request returns with No main power removal. + * PCIe devices which register this notifier shall handle No main power + * removal scenario accordingly. + * + * Return: Returns 0 on success and errno on failure. + */ +int pci_acpi_register_aux_power_notifier(struct notifier_block *nb) +{ + return blocking_notifier_chain_register(&pci_acpi_aux_power_notify_list, nb); +} +EXPORT_SYMBOL_GPL(pci_acpi_register_aux_power_notifier); + +void pci_acpi_unregister_aux_power_notifier(struct notifier_block *nb) +{ + blocking_notifier_chain_unregister(&pci_acpi_aux_power_notify_list, nb); +} +EXPORT_SYMBOL_GPL(pci_acpi_unregister_aux_power_notifier); + /** * pci_acpi_request_d3cold_aux_power - Request D3cold aux power via ACPI DSM * @dev: PCI device instance @@ -1466,17 +1492,19 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power) result = out_obj->integer.value; switch (result) { - case 0x0: + case ACPI_AUX_PW_DENIED: dev_dbg(&dev->dev, "D3cold Aux Power %umW request denied\n", requested_power); break; - case 0x1: + case ACPI_AUX_PW_GRANTED: dev_info(&dev->dev, "D3cold Aux Power request granted: %umW\n", requested_power); ret = 0; break; - case 0x2: + case ACPI_NO_MAIN_PW_REMOVAL: dev_info(&dev->dev, "D3cold Aux Power: Main power won't be removed\n"); + blocking_notifier_call_chain(&pci_acpi_aux_power_notify_list, + ACPI_NO_MAIN_PW_REMOVAL, dev); ret = -EBUSY; break; default: diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h index 4b7373f91a9a..793b979af98b 100644 --- a/include/linux/pci-acpi.h +++ b/include/linux/pci-acpi.h @@ -124,6 +124,10 @@ extern const guid_t pci_acpi_dsm_guid; #define DSM_PCI_D3COLD_AUX_POWER_LIMIT 0x0A #define DSM_PCI_PERST_ASSERTION_DELAY 0x0B +#define ACPI_AUX_PW_DENIED 0x0 +#define ACPI_AUX_PW_GRANTED 0x1 +#define ACPI_NO_MAIN_PW_REMOVAL 0x2 + #ifdef CONFIG_PCIE_EDR void pci_acpi_add_edr_notifier(struct pci_dev *pdev); void pci_acpi_remove_edr_notifier(struct pci_dev *pdev); @@ -134,12 +138,21 @@ static inline void pci_acpi_remove_edr_notifier(struct pci_dev *pdev) { } int pci_acpi_set_companion_lookup_hook(struct acpi_device *(*func)(struct pci_dev *)); void pci_acpi_clear_companion_lookup_hook(void); +int pci_acpi_register_aux_power_notifier(struct notifier_block *nb); +void pci_acpi_unregister_aux_power_notifier(struct notifier_block *nb); int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power); int pci_acpi_add_perst_assertion_delay(struct pci_dev *dev, u32 delay_us); #else /* CONFIG_ACPI */ static inline void acpi_pci_add_bus(struct pci_bus *bus) { } static inline void acpi_pci_remove_bus(struct pci_bus *bus) { } +int pci_acpi_register_aux_power_notifier(struct notifier_block *nb) +{ + return -EOPNOTSUPP; +} + +void pci_acpi_unregister_aux_power_notifier(struct notifier_block *nb) { } + int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power) { return -EOPNOTSUPP;
Adding a notifier to notify all PCIe child devices about the block main power removal. It is needed because theoretically multiple PCIe Endpoint devices on same Root Port can request for AUX power and _DSM method can return with 80000000h signifies that the hierarchy connected via the slot cannot support main power removal when in D3Cold. This may disrupt functionality of other child device. Let's notify all PCIe devices requested Aux power resource and Let PCIe End Point driver handle it in its callback. Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com> --- drivers/pci/pci-acpi.c | 34 +++++++++++++++++++++++++++++++--- include/linux/pci-acpi.h | 13 +++++++++++++ 2 files changed, 44 insertions(+), 3 deletions(-)