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authorYinghai Lu <yinghai@kernel.org>2015-05-28 00:23:51 (GMT)
committerBjorn Helgaas <bhelgaas@google.com>2015-05-29 22:21:45 (GMT)
commit3a9ad0b4fdcd57f775d3615004c8c64c021a9e7d (patch)
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parent5ebe6afaf0057ac3eaeb98defd5456894b446d22 (diff)
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PCI: Add pci_bus_addr_t
David Ahern reported that d63e2e1f3df9 ("sparc/PCI: Clip bridge windows to fit in upstream windows") fails to boot on sparc/T5-8: pci 0000:06:00.0: reg 0x184: can't handle BAR above 4GB (bus address 0x110204000) The problem is that sparc64 assumed that dma_addr_t only needed to hold DMA addresses, i.e., bus addresses returned via the DMA API (dma_map_single(), etc.), while the PCI core assumed dma_addr_t could hold *any* bus address, including raw BAR values. On sparc64, all DMA addresses fit in 32 bits, so dma_addr_t is a 32-bit type. However, BAR values can be 64 bits wide, so they don't fit in a dma_addr_t. d63e2e1f3df9 added new checking that tripped over this mismatch. Add pci_bus_addr_t, which is wide enough to hold any PCI bus address, including both raw BAR values and DMA addresses. This will be 64 bits on 64-bit platforms and on platforms with a 64-bit dma_addr_t. Then dma_addr_t only needs to be wide enough to hold addresses from the DMA API. [bhelgaas: changelog, bugzilla, Kconfig to ensure pci_bus_addr_t is at least as wide as dma_addr_t, documentation] Fixes: d63e2e1f3df9 ("sparc/PCI: Clip bridge windows to fit in upstream windows") Fixes: 23b13bc76f35 ("PCI: Fail safely if we can't handle BARs larger than 4GB") Link: http://lkml.kernel.org/r/CAE9FiQU1gJY1LYrxs+ma5LCTEEe4xmtjRG0aXJ9K_Tsu+m9Wuw@mail.gmail.com Link: http://lkml.kernel.org/r/1427857069-6789-1-git-send-email-yinghai@kernel.org Link: https://bugzilla.kernel.org/show_bug.cgi?id=96231 Reported-by: David Ahern <david.ahern@oracle.com> Tested-by: David Ahern <david.ahern@oracle.com> Signed-off-by: Yinghai Lu <yinghai@kernel.org> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Acked-by: David S. Miller <davem@davemloft.net> CC: stable@vger.kernel.org # v3.19+
Diffstat (limited to 'Documentation/DMA-API.txt')
-rw-r--r--Documentation/DMA-API.txt30
1 files changed, 15 insertions, 15 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 5208840..7eba542 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -18,10 +18,10 @@ Part I - dma_ API
To get the dma_ API, you must #include <linux/dma-mapping.h>. This
provides dma_addr_t and the interfaces described below.
-A dma_addr_t can hold any valid DMA or bus address for the platform. It
-can be given to a device to use as a DMA source or target. A CPU cannot
-reference a dma_addr_t directly because there may be translation between
-its physical address space and the bus address space.
+A dma_addr_t can hold any valid DMA address for the platform. It can be
+given to a device to use as a DMA source or target. A CPU cannot reference
+a dma_addr_t directly because there may be translation between its physical
+address space and the DMA address space.
Part Ia - Using large DMA-coherent buffers
------------------------------------------
@@ -42,7 +42,7 @@ It returns a pointer to the allocated region (in the processor's virtual
address space) or NULL if the allocation failed.
It also returns a <dma_handle> which may be cast to an unsigned integer the
-same width as the bus and given to the device as the bus address base of
+same width as the bus and given to the device as the DMA address base of
the region.
Note: consistent memory can be expensive on some platforms, and the
@@ -193,7 +193,7 @@ dma_map_single(struct device *dev, void *cpu_addr, size_t size,
enum dma_data_direction direction)
Maps a piece of processor virtual memory so it can be accessed by the
-device and returns the bus address of the memory.
+device and returns the DMA address of the memory.
The direction for both APIs may be converted freely by casting.
However the dma_ API uses a strongly typed enumerator for its
@@ -212,20 +212,20 @@ contiguous piece of memory. For this reason, memory to be mapped by
this API should be obtained from sources which guarantee it to be
physically contiguous (like kmalloc).
-Further, the bus address of the memory must be within the
+Further, the DMA address of the memory must be within the
dma_mask of the device (the dma_mask is a bit mask of the
-addressable region for the device, i.e., if the bus address of
-the memory ANDed with the dma_mask is still equal to the bus
+addressable region for the device, i.e., if the DMA address of
+the memory ANDed with the dma_mask is still equal to the DMA
address, then the device can perform DMA to the memory). To
ensure that the memory allocated by kmalloc is within the dma_mask,
the driver may specify various platform-dependent flags to restrict
-the bus address range of the allocation (e.g., on x86, GFP_DMA
-guarantees to be within the first 16MB of available bus addresses,
+the DMA address range of the allocation (e.g., on x86, GFP_DMA
+guarantees to be within the first 16MB of available DMA addresses,
as required by ISA devices).
Note also that the above constraints on physical contiguity and
dma_mask may not apply if the platform has an IOMMU (a device which
-maps an I/O bus address to a physical memory address). However, to be
+maps an I/O DMA address to a physical memory address). However, to be
portable, device driver writers may *not* assume that such an IOMMU
exists.
@@ -296,7 +296,7 @@ reduce current DMA mapping usage or delay and try again later).
dma_map_sg(struct device *dev, struct scatterlist *sg,
int nents, enum dma_data_direction direction)
-Returns: the number of bus address segments mapped (this may be shorter
+Returns: the number of DMA address segments mapped (this may be shorter
than <nents> passed in if some elements of the scatter/gather list are
physically or virtually adjacent and an IOMMU maps them with a single
entry).
@@ -340,7 +340,7 @@ must be the same as those and passed in to the scatter/gather mapping
API.
Note: <nents> must be the number you passed in, *not* the number of
-bus address entries returned.
+DMA address entries returned.
void
dma_sync_single_for_cpu(struct device *dev, dma_addr_t dma_handle, size_t size,
@@ -507,7 +507,7 @@ it's asked for coherent memory for this device.
phys_addr is the CPU physical address to which the memory is currently
assigned (this will be ioremapped so the CPU can access the region).
-device_addr is the bus address the device needs to be programmed
+device_addr is the DMA address the device needs to be programmed
with to actually address this memory (this will be handed out as the
dma_addr_t in dma_alloc_coherent()).