[PATCH RFC] PCI/portdrv: Don't disable pci device during shutdown

[Huacai Chen <chenhc@lemote.com>]

Use separate remove()/shutdown() callback, and don't disable pci device
during shutdown. This can avoid some poweroff/reboot failures.

The poweroff/reboot failures can easily reproduce on Loongson platforms.
I think this is not a Loongson-specific problem, instead, is a problem
related to some specific PCI hosts. On some x86 platforms, radeon/amdgpu
devices can cause the same problem, and commit faefba95c9e8ca3a523831c2e
("drm/amdgpu: just suspend the hw on pci shutdown") can resolve it.

Radeon driver is more difficult than amdgpu due to its confusing symbol
names, and I have maintained an out-of-tree patch for a long time [1].
Recently, we found more and more devices can cause the same problem, and
it is very difficult to modify all problematic drivers as radeon/amdgpu
does. So, I think modify the PCIe port driver is a simple and effective
way.

[1] https://github.com/chenhuacai/linux/commit/6612f9c1fc290d42a14618ce9a7d03014d8ebb1a

Signed-off-by: Huacai Chen <chenhc@lemote.com>
---
 drivers/pci/pcie/portdrv.h      |  2 +-
 drivers/pci/pcie/portdrv_core.c |  6 ++++--
 drivers/pci/pcie/portdrv_pci.c  | 15 +++++++++++++--
 3 files changed, 18 insertions(+), 5 deletions(-)

diff --git a/drivers/pci/pcie/portdrv.h b/drivers/pci/pcie/portdrv.h
index af7cf23..22ba7b9 100644
--- a/drivers/pci/pcie/portdrv.h
+++ b/drivers/pci/pcie/portdrv.h
@@ -123,7 +123,7 @@ int pcie_port_device_resume(struct device *dev);
 int pcie_port_device_runtime_suspend(struct device *dev);
 int pcie_port_device_runtime_resume(struct device *dev);
 #endif
-void pcie_port_device_remove(struct pci_dev *dev);
+void pcie_port_device_remove(struct pci_dev *dev, bool disable);
 int __must_check pcie_port_bus_register(void);
 void pcie_port_bus_unregister(void);
 
diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 50a9522..aa165be 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -487,11 +487,13 @@ EXPORT_SYMBOL_GPL(pcie_port_find_device);
  * Remove PCI Express port service devices associated with given port and
  * disable MSI-X or MSI for the port.
  */
-void pcie_port_device_remove(struct pci_dev *dev)
+void pcie_port_device_remove(struct pci_dev *dev, bool disable)
 {
 	device_for_each_child(&dev->dev, NULL, remove_iter);
 	pci_free_irq_vectors(dev);
-	pci_disable_device(dev);
+
+	if (disable)
+		pci_disable_device(dev);
 }
 
 /**
diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 3acf151..fcd3d2e 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -142,7 +142,18 @@ static void pcie_portdrv_remove(struct pci_dev *dev)
 		pm_runtime_dont_use_autosuspend(&dev->dev);
 	}
 
-	pcie_port_device_remove(dev);
+	pcie_port_device_remove(dev, true);
+}
+
+static void pcie_portdrv_shutdown(struct pci_dev *dev)
+{
+	if (pci_bridge_d3_possible(dev)) {
+		pm_runtime_forbid(&dev->dev);
+		pm_runtime_get_noresume(&dev->dev);
+		pm_runtime_dont_use_autosuspend(&dev->dev);
+	}
+
+	pcie_port_device_remove(dev, false);
 }
 
 static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
@@ -211,7 +222,7 @@ static struct pci_driver pcie_portdriver = {
 
 	.probe		= pcie_portdrv_probe,
 	.remove		= pcie_portdrv_remove,
-	.shutdown	= pcie_portdrv_remove,
+	.shutdown	= pcie_portdrv_shutdown,
 
 	.err_handler	= &pcie_portdrv_err_handler,
 
-- 
2.7.0