[PATCH v6 6/8] PCI: Add support for ACPI _RST reset method

[Amey Narkhede <ameynarkhede03@gmail.com>]

From: Shanker Donthineni <sdonthineni@nvidia.com>

The _RST is a standard method specified in the ACPI specification. It
provides a function level reset when it is described in the acpi_device
context associated with PCI-device. Implement a new reset function
pci_dev_acpi_reset() for probing RST method and execute if it is defined
in the firmware.

The default priority of the ACPI reset is set to below device-specific
and above hardware resets.

Signed-off-by: Shanker Donthineni <sdonthineni@nvidia.com>
Suggested-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Sinan Kaya <okaya@kernel.org>
---
 drivers/pci/pci-acpi.c | 23 +++++++++++++++++++++++
 drivers/pci/pci.c      |  1 +
 drivers/pci/pci.h      |  6 ++++++
 include/linux/pci.h    |  2 +-
 4 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index eaddbf701..40dd24cd3 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -941,6 +941,29 @@ void pci_set_acpi_fwnode(struct pci_dev *dev)
 				   acpi_pci_find_companion(&dev->dev));
 }
 
+/**
+ * pci_dev_acpi_reset - do a function level reset using _RST method
+ * @dev: device to reset
+ * @probe: check if _RST method is included in the acpi_device context.
+ */
+int pci_dev_acpi_reset(struct pci_dev *dev, int probe)
+{
+	acpi_handle handle = ACPI_HANDLE(&dev->dev);
+
+	if (!handle || !acpi_has_method(handle, "_RST"))
+		return -ENOTTY;
+
+	if (probe)
+		return 0;
+
+	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_RST", NULL, NULL))) {
+		pci_warn(dev, "ACPI _RST failed\n");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static bool acpi_pci_bridge_d3(struct pci_dev *dev)
 {
 	const struct fwnode_handle *fwnode;
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index 2302aa421..2e7efd7e7 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5121,6 +5121,7 @@ static void pci_dev_restore(struct pci_dev *dev)
  */
 const struct pci_reset_fn_method pci_reset_fn_methods[] = {
 	{ &pci_dev_specific_reset, .name = "device_specific" },
+	{ &pci_dev_acpi_reset, .name = "acpi" },
 	{ &pcie_reset_flr, .name = "flr" },
 	{ &pci_af_flr, .name = "af_flr" },
 	{ &pci_pm_reset, .name = "pm" },
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index d22da6d3c..e9cfb7cd6 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -704,7 +704,13 @@ static inline int pci_aer_raw_clear_status(struct pci_dev *dev) { return -EINVAL
 int pci_acpi_program_hp_params(struct pci_dev *dev);
 extern const struct attribute_group pci_dev_acpi_attr_group;
 void pci_set_acpi_fwnode(struct pci_dev *dev);
+int pci_dev_acpi_reset(struct pci_dev *dev, int probe);
 #else
+static inline int pci_dev_acpi_reset(struct pci_dev *dev, int probe)
+{
+	return -ENOTTY;
+}
+
 static inline void pci_set_acpi_fwnode(struct pci_dev *dev) {}
 static inline int pci_acpi_program_hp_params(struct pci_dev *dev)
 {
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 6e9bc4f9c..a7f063da2 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -49,7 +49,7 @@
 			       PCI_STATUS_SIG_TARGET_ABORT | \
 			       PCI_STATUS_PARITY)
 
-#define PCI_RESET_METHODS_NUM 5
+#define PCI_RESET_METHODS_NUM 6
 
 /*
  * The PCI interface treats multi-function devices as independent
-- 
2.31.1