linux-kernel - [PATCH 2/3] PCI/ACPI: Add API for specifying aux power in D3cold

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Message-ID: <20231110185503.46117-3-mario.limonciello@amd.com>
Date:   Fri, 10 Nov 2023 12:55:02 -0600
From:   Mario Limonciello <mario.limonciello@....com>
To:     Bjorn Helgaas <bhelgaas@...gle.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
CC:     "open list:PCI SUBSYSTEM" <linux-pci@...r.kernel.org>,
        <linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "Mario Limonciello" <mario.limonciello@....com>
Subject: [PATCH 2/3] PCI/ACPI: Add API for specifying aux power in D3cold

The PCI firmware specification includes support for a _DSM function
to negotiate aux power to be provided to the device while it is in
D3cold.

"The Request D3cold Aux Power Limit function describes how a device
driver conveys its auxiliary  power requirements to the host platform
when the device is in D3cold. The system firmware responds with a value
indicating whether the request can be supported. The power request is
specific to the Auxiliary power supply; main power may be removed while
in D3cold. A device must not draw any more power than what has been
negotiated via this mechanism after entering D3cold"

Add API for callers to utilize this _DSM.

Link: https://members.pcisig.com/wg/PCI-SIG/document/15350
      PCI Firmware specification 3.3, section 4.6.10
Signed-off-by: Mario Limonciello <mario.limonciello@....com>
---
 drivers/pci/pci-acpi.c   | 54 ++++++++++++++++++++++++++++++++++++++++
 include/linux/pci-acpi.h |  7 ++++++
 2 files changed, 61 insertions(+)

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index bea72e807817..257858a6719e 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1348,6 +1348,60 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev)
 	return adev;
 }
 
+/**
+ * pci_acpi_request_aux_power_for_d3cold - Request auxiliary power for D3cold
+ * @pdev: PCI device to request power for
+ * @arg: mW requested
+ *
+ * This function requests auxiliary power for a PCI device in D3cold state
+ * when main power is removed above the value guaranteed by PCI specification.
+ *
+ * Return:
+ *  0 on success
+ *  -ENODEV when the device does not support the _DSM
+ *  -EIO on ACPI call failure
+ *  -EACCESS when the request was denied
+ *  Positive value corresponding to platform requested retry interval in seconds
+ */
+int pci_acpi_request_aux_power_for_d3cold(struct pci_dev *pdev, int arg)
+{
+	struct acpi_device *adev = ACPI_COMPANION(&pdev->dev);
+	union acpi_object *obj;
+	union acpi_object argv4 = {
+		.integer.type = ACPI_TYPE_INTEGER,
+		.integer.value = arg,
+	};
+	int val;
+
+	if (!acpi_check_dsm(adev->handle, &pci_acpi_dsm_guid,
+			    pci_acpi_dsm_rev,
+			    1 << DSM_PCI_REQUEST_D3COLD_AUX_POWER))
+		return -ENODEV;
+
+	obj = acpi_evaluate_dsm_typed(adev->handle, &pci_acpi_dsm_guid,
+				      pci_acpi_dsm_rev,
+				      DSM_PCI_REQUEST_D3COLD_AUX_POWER,
+				      &argv4, ACPI_TYPE_INTEGER);
+	if (!obj)
+		return -EIO;
+
+	val = obj->integer.value;
+	ACPI_FREE(obj);
+
+	switch (val) {
+	case PCI_D3COLD_AUX_DENIED:
+		return -EACCES;
+	case PCI_D3COLD_AUX_GRANTED:
+	case PCI_D3COLD_AUX_NO_MAIN_POWER_REMOVAL:
+		return 0;
+	default:
+		break;
+	}
+
+	return val;
+}
+EXPORT_SYMBOL_GPL(pci_acpi_request_aux_power_for_d3cold);
+
 /**
  * pci_acpi_optimize_delay - optimize PCI D3 and D3cold delay from ACPI
  * @pdev: the PCI device whose delay is to be updated
diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h
index 7966ef8f14b3..bc6372bcb7d6 100644
--- a/include/linux/pci-acpi.h
+++ b/include/linux/pci-acpi.h
@@ -122,6 +122,13 @@ extern const int pci_acpi_dsm_rev;
 #define DSM_PCI_DEVICE_NAME			0x07
 #define DSM_PCI_POWER_ON_RESET_DELAY		0x08
 #define DSM_PCI_DEVICE_READINESS_DURATIONS	0x09
+#define DSM_PCI_REQUEST_D3COLD_AUX_POWER	0x0A
+
+#define PCI_D3COLD_AUX_DENIED			0
+#define PCI_D3COLD_AUX_GRANTED			1
+#define PCI_D3COLD_AUX_NO_MAIN_POWER_REMOVAL	2
+
+int pci_acpi_request_aux_power_for_d3cold(struct pci_dev *pdev, int arg);
 
 #ifdef CONFIG_PCIE_EDR
 void pci_acpi_add_edr_notifier(struct pci_dev *pdev);
-- 
2.34.1