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Date:   Mon, 9 Jan 2023 16:35:25 +0800 (CST)
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bridge base/limit(memory behind in lspci info, outbound pcie address/size)
region is used to route outbound mem read/write transaction to ep. This
base/limit region also may filter out inbound transactions which will
result in inbound(eg: dma) transaction fail.

For example, if bridge base/limit is [0x20000000, 0x203fffff], system ram
is [0x20000000, 0x27ffffff]. The inbound mapping is usually 1:1 equal
mapping. When allocated system ram for inbound tansaction is 0x20004000
(any in bridge base/limit), this inbound transactions will be filter out.

AER may report 'UnsupReq' on inbound mem read/write transactions if address
is in this base/limit region, but not all pcie AER enabled or work well. We
warn it also in bridge pci address setting phase.

Signed-off-by: Chen Lin <chen.lin5@zte.com.cn>
---
 drivers/pci/setup-bus.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index b4096598dbcb..1a9f527d2317 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -608,6 +608,24 @@ static void pci_setup_bridge_io(struct pci_dev *bridge)
 	pci_write_config_dword(bridge, PCI_IO_BASE_UPPER16, io_upper16);
 }

+static void check_bridge_region_overlaps_systemram(struct pci_dev *bridge,
+							struct pci_bus_region *region)
+{
+	int is_ram;
+
+	/*
+	 * bridge base/limit(memory behind) region may filter out inbound
+	 * transactions which will result in inbound(eg: dma) fail of ep.
+	 * AER may report it if enabled, we warn it also.
+	 */
+	is_ram = region_intersects(region->start, region->end - region->start + 1,
+				IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
+	if (is_ram == REGION_INTERSECTS) {
+		pci_warn(bridge, "%#012llx..%#012llx bridge base/limit region overlaps with system ram, may result in inbound fail\n",
+			region->start, region->end);
+	}
+}
+
 static void pci_setup_bridge_mmio(struct pci_dev *bridge)
 {
 	struct resource *res;
@@ -621,6 +639,7 @@ static void pci_setup_bridge_mmio(struct pci_dev *bridge)
 		l = (region.start >> 16) & 0xfff0;
 		l |= region.end & 0xfff00000;
 		pci_info(bridge, "  bridge window %pR\n", res);
+		check_bridge_region_overlaps_systemram(bridge, &region);
 	} else {
 		l = 0x0000fff0;
 	}
@@ -652,6 +671,7 @@ static void pci_setup_bridge_mmio_pref(struct pci_dev *bridge)
 			lu = upper_32_bits(region.end);
 		}
 		pci_info(bridge, "  bridge window %pR\n", res);
+		check_bridge_region_overlaps_systemram(bridge, &region);
 	} else {
 		l = 0x0000fff0;
 	}
-- 
2.15.2