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[2/3] PCI/xilinx: Work-around for hardware DMA limit (32 bits)

Message ID 20180619141700.7842-3-hch@lst.de (mailing list archive)
State New, archived
Delegated to: Bjorn Helgaas
Headers show

Commit Message

Christoph Hellwig June 19, 2018, 2:16 p.m. UTC 
From: "Wesley W. Terpstra" <wesley@sifive.com>

This PCIe bridge only has a 32 bit bus master interface, thus truncating
the DMA capability of all PCIe devices attached beneath it. This caps
the child device capability so that these devices work on systems with
physical memory beyond the 4GiB threshold.

Signed-off-by: Wesley W. Terpstra <wesley@sifive.com>
[hch: switched to setting the dma_32bit_limit flag instead of overriding
 the dma_map_ops]
Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 drivers/pci/controller/pcie-xilinx.c | 10 ++++++++++
 1 file changed, 10 insertions(+)
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Patch

diff --git a/drivers/pci/controller/pcie-xilinx.c b/drivers/pci/controller/pcie-xilinx.c
index b110a3a814e3..f6b41df59886 100644
--- a/drivers/pci/controller/pcie-xilinx.c
+++ b/drivers/pci/controller/pcie-xilinx.c
@@ -197,11 +197,21 @@  static void __iomem *xilinx_pcie_map_bus(struct pci_bus *bus,
 	return port->reg_base + relbus + where;
 }
 
+/*
+ * This PCIe bridge only has a 32 bit bus master interface, thus truncating
+ * the DMA capability of all PCIe devices attached beneath it.
+ */
+static void xilinx_pcie_add_dev(struct pci_dev *pdev, struct pci_bus *bus)
+{
+	pdev->dev.dma_32bit_limit = true;
+}
+
 /* PCIe operations */
 static struct pci_ops xilinx_pcie_ops = {
 	.map_bus = xilinx_pcie_map_bus,
 	.read	= pci_generic_config_read,
 	.write	= pci_generic_config_write,
+	.add_dev = xilinx_pcie_add_dev,
 };
 
 /* MSI functions */