Re: [PATCH v4 02/11] PCI/ACPI: Per root port allow one Aux power limit request

[Sathyanarayanan Kuppuswamy <sathyanarayanan.kuppuswamy@linux.intel.com>]

On 5/29/25 4:16 AM, Badal Nilawar wrote:
> For given root port allow one Aux power limit request.
>
> 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 */


Do you need a new lock ? Is it possible to reuse existing mutex like device_lock()?


>   };
>   
>   struct acpi_dep_data {

-- 
Sathyanarayanan Kuppuswamy
Linux Kernel Developer