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.
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.
> Cc: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> Cc: Anshuman Gupta <anshuman.gupta@xxxxxxxxx>
> Signed-off-by: Badal Nilawar <badal.nilawar@xxxxxxxxx>
> ---
> 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
>
