[PATCH V14 6/7] PCI: Add quirk for LS7A to avoid reboot failure

[Huacai Chen <chenhuacai@loongson.cn>]

cc27b735ad3a7557 ("PCI/portdrv: Turn off PCIe services during shutdown")
causes poweroff/reboot failure on systems with LS7A chipset. We found
that if we remove "pci_command &= ~PCI_COMMAND_MASTER" in do_pci_disable
_device(), it can work well. The hardware engineer says that the root
cause is that CPU is still accessing PCIe devices while poweroff/reboot,
and if we disable the Bus Master Bit at this time, the PCIe controller
doesn't forward requests to downstream devices, and also does not send
TIMEOUT to CPU, which causes CPU wait forever (hardware deadlock). This
behavior is a PCIe protocol violation (Bus Master should not be involved
in CPU MMIO transactions), and it will be fixed in new revisions of
hardware (add timeout mechanism for CPU read request, whether or not Bus
Master bit is cleared).

On some x86 platforms, radeon/amdgpu devices can cause similar problems
[1][2]. Once before I wanted to make a single patch to solve "all of
these problems" together, but it seems unreasonable because maybe they
are not exactly the same problem. So, this patch add a new function
pcie_portdrv_shutdown(), a slight modified copy of pcie_portdrv_remove()
dedicated for the shutdown path, and then add a quirk just for LS7A to
avoid clearing Bus Master bit in pcie_portdrv_shutdown(). Leave other
platforms behave as before.

[1] https://bugs.freedesktop.org/show_bug.cgi?id=97980
[2] https://bugs.freedesktop.org/show_bug.cgi?id=98638

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
---
 drivers/pci/controller/pci-loongson.c | 17 +++++++++++++++++
 drivers/pci/pcie/portdrv_core.c       |  1 -
 drivers/pci/pcie/portdrv_pci.c        | 20 +++++++++++++++++++-
 include/linux/pci.h                   |  1 +
 4 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/drivers/pci/controller/pci-loongson.c b/drivers/pci/controller/pci-loongson.c
index 62ac91b2a5c5..6d7276debcfd 100644
--- a/drivers/pci/controller/pci-loongson.c
+++ b/drivers/pci/controller/pci-loongson.c
@@ -85,6 +85,23 @@ DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
 			DEV_PCIE_PORT_2, loongson_mrrs_quirk);
 
+static void loongson_bmaster_quirk(struct pci_dev *pdev)
+{
+	/*
+	 * Some Loongson PCIe ports will cause CPU deadlock if disable
+	 * the Bus Master bit during poweroff/reboot.
+	 */
+	struct pci_host_bridge *bridge = pci_find_host_bridge(pdev->bus);
+
+	bridge->no_dis_bmaster = 1;
+}
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_0, loongson_bmaster_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_1, loongson_bmaster_quirk);
+DECLARE_PCI_FIXUP_EARLY(PCI_VENDOR_ID_LOONGSON,
+			DEV_PCIE_PORT_2, loongson_bmaster_quirk);
+
 static struct loongson_pci *pci_bus_to_loongson_pci(struct pci_bus *bus)
 {
 	struct pci_config_window *cfg;
diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index 604feeb84ee4..ee3d654dcbb4 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -493,7 +493,6 @@ void pcie_port_device_remove(struct pci_dev *dev)
 {
 	device_for_each_child(&dev->dev, NULL, remove_iter);
 	pci_free_irq_vectors(dev);
-	pci_disable_device(dev);
 }
 
 /**
diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
index 7f8788a970ae..f821f916d020 100644
--- a/drivers/pci/pcie/portdrv_pci.c
+++ b/drivers/pci/pcie/portdrv_pci.c
@@ -148,6 +148,24 @@ static void pcie_portdrv_remove(struct pci_dev *dev)
 	}
 
 	pcie_port_device_remove(dev);
+
+	pci_disable_device(dev);
+}
+
+static void pcie_portdrv_shutdown(struct pci_dev *dev)
+{
+	struct pci_host_bridge *bridge = pci_find_host_bridge(dev->bus);
+
+	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);
+
+	if (!bridge->no_dis_bmaster)
+		pci_disable_device(dev);
 }
 
 static pci_ers_result_t pcie_portdrv_error_detected(struct pci_dev *dev,
@@ -198,7 +216,7 @@ 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,
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index a9211074add6..0f0908679074 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -570,6 +570,7 @@ struct pci_host_bridge {
 	unsigned int	ignore_reset_delay:1;	/* For entire hierarchy */
 	unsigned int	no_ext_tags:1;		/* No Extended Tags */
 	unsigned int	no_inc_mrrs:1;		/* No Increase MRRS */
+	unsigned int	no_dis_bmaster:1;	/* No Disable Bus Master */
 	unsigned int	native_aer:1;		/* OS may use PCIe AER */
 	unsigned int	native_pcie_hotplug:1;	/* OS may use PCIe hotplug */
 	unsigned int	native_shpc_hotplug:1;	/* OS may use SHPC hotplug */
-- 
2.27.0