[PATCH v2] PCI: Call _REG when saving/restoring PCI state

[Mario Limonciello]

ASMedia PCIe GPIO controllers fail functional tests after returning from
suspend (S3 or s2idle). This is because the BIOS checks whether the
OSPM has called the `_REG` method to determine whether it can interact with
the OperationRegion assigned to the device.

As described in 6.5.4 in the APCI spec, `_REG` is used to inform the AML
code on the availability of an operation region.

To fix this issue, call acpi_evaluate_reg() when saving and restoring the
state of PCI devices.

Link: https://uefi.org/htmlspecs/ACPI_Spec_6_4_html/06_Device_Configuration/Device_Configuration.html#reg-region
Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx>
---
v1->v2:
 * Handle case of no CONFIG_ACPI
 * Rename function
 * Update commit message
 * Move ACPI calling code into pci-acpi.c instead
 * Cite the ACPI spec
---
 drivers/pci/pci-acpi.c | 10 ++++++++++
 drivers/pci/pci.c      | 14 ++++++++++++++
 drivers/pci/pci.h      |  2 ++
 3 files changed, 26 insertions(+)

diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 1698205dd73c..abc8bcfc2c71 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -1209,6 +1209,16 @@ void acpi_pci_remove_bus(struct pci_bus *bus)
 	acpi_pci_slot_remove(bus);
 }
 
+void acpi_pci_set_register_access(struct pci_dev *dev, bool enable)
+{
+	int val = enable ? ACPI_REG_CONNECT : ACPI_REG_DISCONNECT;
+	int ret = acpi_evaluate_reg(ACPI_HANDLE(&dev->dev),
+				    ACPI_ADR_SPACE_PCI_CONFIG, val);
+	if (ret)
+		pci_dbg(dev, "ACPI _REG %s evaluation failed (%d)\n",
+			val ? "connect" : "disconnect", ret);
+}
+
 /* ACPI bus type */
 
 
diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
index e38c2f6eebd4..b2f1f603ec62 100644
--- a/drivers/pci/pci.c
+++ b/drivers/pci/pci.c
@@ -1068,6 +1068,14 @@ static inline bool platform_pci_bridge_d3(struct pci_dev *dev)
 	return acpi_pci_bridge_d3(dev);
 }
 
+static inline void platform_set_register_access(struct pci_dev *dev, bool en)
+{
+	if (pci_use_mid_pm())
+		return;
+
+	acpi_pci_set_register_access(dev, en);
+}
+
 /**
  * pci_update_current_state - Read power state of given device and cache it
  * @dev: PCI device to handle.
@@ -1645,6 +1653,9 @@ static void pci_restore_ltr_state(struct pci_dev *dev)
 int pci_save_state(struct pci_dev *dev)
 {
 	int i;
+
+	platform_set_register_access(dev, false);
+
 	/* XXX: 100% dword access ok here? */
 	for (i = 0; i < 16; i++) {
 		pci_read_config_dword(dev, i * 4, &dev->saved_config_space[i]);
@@ -1790,6 +1801,8 @@ void pci_restore_state(struct pci_dev *dev)
 	pci_enable_acs(dev);
 	pci_restore_iov_state(dev);
 
+	platform_set_register_access(dev, true);
+
 	dev->state_saved = false;
 }
 EXPORT_SYMBOL(pci_restore_state);
@@ -3203,6 +3216,7 @@ void pci_pm_init(struct pci_dev *dev)
 	pci_read_config_word(dev, PCI_STATUS, &status);
 	if (status & PCI_STATUS_IMM_READY)
 		dev->imm_ready = 1;
+	platform_set_register_access(dev, true);
 }
 
 static unsigned long pci_ea_flags(struct pci_dev *dev, u8 prop)
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index ffccb03933e2..78961505aae2 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -703,6 +703,7 @@ void acpi_pci_refresh_power_state(struct pci_dev *dev);
 int acpi_pci_wakeup(struct pci_dev *dev, bool enable);
 bool acpi_pci_need_resume(struct pci_dev *dev);
 pci_power_t acpi_pci_choose_state(struct pci_dev *pdev);
+void acpi_pci_set_register_access(struct pci_dev *dev, bool enable);
 #else
 static inline int pci_dev_acpi_reset(struct pci_dev *dev, bool probe)
 {
@@ -742,6 +743,7 @@ static inline pci_power_t acpi_pci_choose_state(struct pci_dev *pdev)
 {
 	return PCI_POWER_ERROR;
 }
+static inline void acpi_pci_set_register_access(struct pci_dev *dev, bool enable) {}
 #endif
 
 #ifdef CONFIG_PCIEASPM
-- 
2.34.1