[PATCH v5 5/7] PCI: Add support for a function level reset based on _RST method

[Amey Narkhede]

From: Shanker Donthineni <sdonthineni@xxxxxxxxxx>

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 ACPI binding
information is available only after calling device_add(). To consider
_RST method, move pci_init_reset_methods() to end of pci_device_add()
and craete two sysfs entries reset & reset_methond from
pci_create_sysfs_dev_files()

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

Signed-off-by: Shanker Donthineni <sdonthineni@xxxxxxxxxx>
Reviewed-by: Sinan Kaya <okaya@xxxxxxxxxx>
---
 drivers/pci/pci-sysfs.c | 23 ++++++++++++++++++++---
 drivers/pci/pci.c       | 30 ++++++++++++++++++++++++++++++
 drivers/pci/probe.c     |  2 +-
 include/linux/pci.h     |  2 +-
 4 files changed, 52 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pci-sysfs.c b/drivers/pci/pci-sysfs.c
index 04b3d6565..b332d7923 100644
--- a/drivers/pci/pci-sysfs.c
+++ b/drivers/pci/pci-sysfs.c
@@ -1482,12 +1482,30 @@ static const struct attribute_group pci_dev_reset_attr_group = {
 	.is_visible = pci_dev_reset_attr_is_visible,
 };
 
+const struct attribute_group *pci_dev_reset_groups[] = {
+	&pci_dev_reset_attr_group,
+	&pci_dev_reset_method_attr_group,
+	NULL,
+};
+
 int __must_check pci_create_sysfs_dev_files(struct pci_dev *pdev)
 {
+	int retval;
+
 	if (!sysfs_initialized)
 		return -EACCES;
 
-	return pci_create_resource_files(pdev);
+	retval = pci_create_resource_files(pdev);
+	if (retval)
+		return retval;
+
+	retval = device_add_groups(&pdev->dev, pci_dev_reset_groups);
+	if (retval) {
+		pci_remove_resource_files(pdev);
+		return retval;
+	}
+
+	return 0;
 }
 
 /**
@@ -1501,6 +1519,7 @@ void pci_remove_sysfs_dev_files(struct pci_dev *pdev)
 	if (!sysfs_initialized)
 		return;
 
+	device_remove_groups(&pdev->dev, pci_dev_reset_groups);
 	pci_remove_resource_files(pdev);
 }
 
@@ -1594,8 +1613,6 @@ const struct attribute_group *pci_dev_groups[] = {
 	&pci_dev_group,
 	&pci_dev_config_attr_group,
 	&pci_dev_rom_attr_group,
-	&pci_dev_reset_attr_group,
-	&pci_dev_reset_method_attr_group,
 	&pci_dev_vpd_attr_group,
 #ifdef CONFIG_DMI
 	&pci_dev_smbios_attr_group,
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index bbed852d9..4a7019d0b 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -5115,6 +5115,35 @@ static void pci_dev_restore(struct pci_dev *dev)
 		err_handler->reset_done(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.
+ */
+static int pci_dev_acpi_reset(struct pci_dev *dev, int probe)
+{
+#ifdef CONFIG_ACPI
+	acpi_handle handle = ACPI_HANDLE(&dev->dev);
+
+	/* Return -ENOTTY if _RST method is not included in the dev context */
+	if (!handle || !acpi_has_method(handle, "_RST"))
+		return -ENOTTY;
+
+	/* Return 0 for probe phase indicating that we can reset this device */
+	if (probe)
+		return 0;
+
+	/* Invoke _RST() method to perform a function level reset */
+	if (ACPI_FAILURE(acpi_evaluate_object(handle, "_RST", NULL, NULL))) {
+		pci_warn(dev, "Failed to reset the device\n");
+		return -EINVAL;
+	}
+	return 0;
+#else
+	return -ENOTTY;
+#endif
+}
+
 /*
  * The ordering for functions in pci_reset_fn_methods
  * is required for reset_methods byte array defined
@@ -5122,6 +5151,7 @@ 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/probe.c b/drivers/pci/probe.c
index 90fd4f61f..eeab791a0 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -2404,7 +2404,6 @@ static void pci_init_capabilities(struct pci_dev *dev)
 	pci_rcec_init(dev);		/* Root Complex Event Collector */
 
 	pcie_report_downtraining(dev);
-	pci_init_reset_methods(dev);
 }
 
 /*
@@ -2495,6 +2494,7 @@ void pci_device_add(struct pci_dev *dev, struct pci_bus *bus)
 	dev->match_driver = false;
 	ret = device_add(&dev->dev);
 	WARN_ON(ret < 0);
+	pci_init_reset_methods(dev);
 }
 
 struct pci_dev *pci_scan_single_device(struct pci_bus *bus, int devfn)
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