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charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit On 05-09-2025 00:06, Bjorn Helgaas wrote: > On Thu, May 29, 2025 at 04:46:45PM +0530, Badal Nilawar wrote: >> For given root port allow one Aux power limit request. > Please include the reason why we do this. I don't think we need it.  This is added as aggregation is not supported. I will add the reason. > > PCI Firmware r3.3, sec 4.6.10 says this _DSM function can be invoked > multiple times with different requests. > > We might need a mutex just to avoid concurrent evaluations of this > _DSM function by different drivers; I'm not sure whether there's a > requirement to avoid that or whether the ACPI core already enforces > something like that. But that would be a separate thing from > aux_power_limit. As discussed in patch1 as driver's pci_dev  will be passed to pci_acpi_request_d3cold_aux_power(), will save that |pci_dev| in |struct acpi_device_power| to support multiple |_DSM| invocations by the same driver. Thanks, Badal > >> Cc: Rafael J. Wysocki >> Cc: Anshuman Gupta >> Signed-off-by: Badal Nilawar >> --- >> drivers/acpi/scan.c | 1 + >> drivers/pci/pci-acpi.c | 25 ++++++++++++++++++++++++- >> include/acpi/acpi_bus.h | 2 ++ >> 3 files changed, 27 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c >> index fb1fe9f3b1a3..9ae7be9db01a 100644 >> --- a/drivers/acpi/scan.c >> +++ b/drivers/acpi/scan.c >> @@ -745,6 +745,7 @@ int acpi_device_add(struct acpi_device *device) >> INIT_LIST_HEAD(&device->physical_node_list); >> INIT_LIST_HEAD(&device->del_list); >> mutex_init(&device->physical_node_lock); >> + mutex_init(&device->power.aux_pwr_lock); >> >> mutex_lock(&acpi_device_lock); >> >> diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c >> index 87f30910a5f1..d33efba4ca94 100644 >> --- a/drivers/pci/pci-acpi.c >> +++ b/drivers/pci/pci-acpi.c >> @@ -1451,6 +1451,7 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power, >> union acpi_object *out_obj; >> acpi_handle handle; >> int result, ret = -EINVAL; >> + struct acpi_device *adev; >> >> if (!dev || !retry_interval) >> return -EINVAL; >> @@ -1464,11 +1465,27 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power, >> return -ENODEV; >> } >> >> + adev = ACPI_COMPANION(&dev->dev); >> + if (!adev) >> + return -EINVAL; >> + >> + mutex_lock(&adev->power.aux_pwr_lock); >> + >> + /* Check if aux power already granted */ >> + if (adev->power.aux_power_limit) { >> + pci_info(dev, "D3cold Aux Power request already granted: %u mW\n", >> + adev->power.aux_power_limit); >> + mutex_unlock(&adev->power.aux_pwr_lock); >> + return -EPERM; >> + } >> + >> out_obj = acpi_evaluate_dsm_typed(handle, &pci_acpi_dsm_guid, 4, >> DSM_PCI_D3COLD_AUX_POWER_LIMIT, >> &in_obj, ACPI_TYPE_INTEGER); >> - if (!out_obj) >> + if (!out_obj) { >> + mutex_unlock(&adev->power.aux_pwr_lock); >> return -EINVAL; >> + } >> >> result = out_obj->integer.value; >> if (retry_interval) >> @@ -1478,14 +1495,17 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power, >> case 0x0: >> pci_dbg(dev, "D3cold Aux Power %u mW request denied\n", >> requested_power); >> + adev->power.aux_power_limit = 0; >> break; >> case 0x1: >> pci_info(dev, "D3cold Aux Power request granted: %u mW\n", >> requested_power); >> + adev->power.aux_power_limit = requested_power; >> ret = 0; >> break; >> case 0x2: >> pci_info(dev, "D3cold Aux Power: Main power won't be removed\n"); >> + adev->power.aux_power_limit = 0; >> ret = -EBUSY; >> break; >> default: >> @@ -1500,9 +1520,12 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power, >> pci_err(dev, "D3cold Aux Power: Reserved or unsupported response: 0x%x\n", >> result); >> } >> + adev->power.aux_power_limit = 0; >> break; >> } >> >> + mutex_unlock(&adev->power.aux_pwr_lock); >> + >> ACPI_FREE(out_obj); >> return ret; >> } >> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h >> index aad1a95e6863..c4ce3d84be00 100644 >> --- a/include/acpi/acpi_bus.h >> +++ b/include/acpi/acpi_bus.h >> @@ -294,6 +294,8 @@ struct acpi_device_power { >> struct acpi_device_power_flags flags; >> struct acpi_device_power_state states[ACPI_D_STATE_COUNT]; /* Power states (D0-D3Cold) */ >> u8 state_for_enumeration; /* Deepest power state for enumeration */ >> + u32 aux_power_limit; /* aux power limit granted by bios */ >> + struct mutex aux_pwr_lock; /* prevent concurrent aux power limit requests */ >> }; >> >> struct acpi_dep_data { >> -- >> 2.34.1 >> --------------fN6Y1dzNJEWhXZJs03x9YO5Z Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: 8bit


On 05-09-2025 00:06, Bjorn Helgaas wrote:
On Thu, May 29, 2025 at 04:46:45PM +0530, Badal Nilawar wrote:

For given root port allow one Aux power limit request.

Please include the reason why we do this.  I don't think we need it.

 This is added as aggregation is not supported. I will add the reason.


PCI Firmware r3.3, sec 4.6.10 says this _DSM function can be invoked
multiple times with different requests.

We might need a mutex just to avoid concurrent evaluations of this
_DSM function by different drivers; I'm not sure whether there's a
requirement to avoid that or whether the ACPI core already enforces
something like that.  But that would be a separate thing from
aux_power_limit.

As discussed in patch1 as driver's pci_dev  will be passed to pci_acpi_request_d3cold_aux_power(), will save that pci_dev in struct acpi_device_power to support multiple _DSM invocations by the same driver.

Thanks,
Badal 



Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Anshuman Gupta <anshuman.gupta@intel.com>
Signed-off-by: Badal Nilawar <badal.nilawar@intel.com>
---
 drivers/acpi/scan.c     |  1 +
 drivers/pci/pci-acpi.c  | 25 ++++++++++++++++++++++++-
 include/acpi/acpi_bus.h |  2 ++
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index fb1fe9f3b1a3..9ae7be9db01a 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -745,6 +745,7 @@ int acpi_device_add(struct acpi_device *device)
 	INIT_LIST_HEAD(&device->physical_node_list);
 	INIT_LIST_HEAD(&device->del_list);
 	mutex_init(&device->physical_node_lock);
+	mutex_init(&device->power.aux_pwr_lock);
 
 	mutex_lock(&acpi_device_lock);
 
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 87f30910a5f1..d33efba4ca94 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1451,6 +1451,7 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power,
 	union acpi_object *out_obj;
 	acpi_handle handle;
 	int result, ret = -EINVAL;
+	struct acpi_device *adev;
 
 	if (!dev || !retry_interval)
 		return -EINVAL;
@@ -1464,11 +1465,27 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power,
 		return -ENODEV;
 	}
 
+	adev = ACPI_COMPANION(&dev->dev);
+	if (!adev)
+		return -EINVAL;
+
+	mutex_lock(&adev->power.aux_pwr_lock);
+
+	/* Check if aux power already granted */
+	if (adev->power.aux_power_limit) {
+		pci_info(dev, "D3cold Aux Power request already granted: %u mW\n",
+			 adev->power.aux_power_limit);
+		mutex_unlock(&adev->power.aux_pwr_lock);
+		return -EPERM;
+	}
+
 	out_obj = acpi_evaluate_dsm_typed(handle, &pci_acpi_dsm_guid, 4,
 					  DSM_PCI_D3COLD_AUX_POWER_LIMIT,
 					  &in_obj, ACPI_TYPE_INTEGER);
-	if (!out_obj)
+	if (!out_obj) {
+		mutex_unlock(&adev->power.aux_pwr_lock);
 		return -EINVAL;
+	}
 
 	result = out_obj->integer.value;
 	if (retry_interval)
@@ -1478,14 +1495,17 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power,
 	case 0x0:
 		pci_dbg(dev, "D3cold Aux Power %u mW request denied\n",
 			requested_power);
+		adev->power.aux_power_limit = 0;
 		break;
 	case 0x1:
 		pci_info(dev, "D3cold Aux Power request granted: %u mW\n",
 			 requested_power);
+		adev->power.aux_power_limit = requested_power;
 		ret = 0;
 		break;
 	case 0x2:
 		pci_info(dev, "D3cold Aux Power: Main power won't be removed\n");
+		adev->power.aux_power_limit = 0;
 		ret = -EBUSY;
 		break;
 	default:
@@ -1500,9 +1520,12 @@ int pci_acpi_request_d3cold_aux_power(struct pci_dev *dev, u32 requested_power,
 			pci_err(dev, "D3cold Aux Power: Reserved or unsupported response: 0x%x\n",
 				result);
 		}
+		adev->power.aux_power_limit = 0;
 		break;
 	}
 
+	mutex_unlock(&adev->power.aux_pwr_lock);
+
 	ACPI_FREE(out_obj);
 	return ret;
 }
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index aad1a95e6863..c4ce3d84be00 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -294,6 +294,8 @@ struct acpi_device_power {
 	struct acpi_device_power_flags flags;
 	struct acpi_device_power_state states[ACPI_D_STATE_COUNT];	/* Power states (D0-D3Cold) */
 	u8 state_for_enumeration; /* Deepest power state for enumeration */
+	u32 aux_power_limit;		/* aux power limit granted by bios */
+	struct mutex aux_pwr_lock;	/* prevent concurrent aux power limit requests */
 };
 
 struct acpi_dep_data {
-- 
2.34.1
--------------fN6Y1dzNJEWhXZJs03x9YO5Z--