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PCI: remove pci_dac_dma_... APIs

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Based on replies to a respective query, remove the pci_dac_dma_...() APIs
(except for pci_dac_dma_supported() on Alpha, where this function is used
in non-DAC PCI DMA code).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Jesse Barnes <jesse.barnes@intel.com>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: David Miller <davem@davemloft.net>
Cc: Jeff Garzik <jeff@garzik.org>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Jan Beulich
2007-07-09 11:55:51 -07:00
committed by Greg Kroah-Hartman
parent b7b095c154
commit caa5171622
24 changed files with 7 additions and 464 deletions
Download Patch File Download Diff File Expand all files Collapse all files
Documentation/DMA-mapping.txt
-103
View File
@@ -664,109 +664,6 @@ It is that simple.
Well, not for some odd devices. See the next section for information
about that.
DAC Addressing for Address Space Hungry Devices
There exists a class of devices which do not mesh well with the PCI
DMA mapping API. By definition these "mappings" are a finite
resource. The number of total available mappings per bus is platform
specific, but there will always be a reasonable amount.
What is "reasonable"? Reasonable means that networking and block I/O
devices need not worry about using too many mappings.
As an example of a problematic device, consider compute cluster cards.
They can potentially need to access gigabytes of memory at once via
DMA. Dynamic mappings are unsuitable for this kind of access pattern.
To this end we've provided a small API by which a device driver
may use DAC cycles to directly address all of physical memory.
Not all platforms support this, but most do. It is easy to determine
whether the platform will work properly at probe time.
First, understand that there may be a SEVERE performance penalty for
using these interfaces on some platforms. Therefore, you MUST only
use these interfaces if it is absolutely required. %99 of devices can
use the normal APIs without any problems.
Note that for streaming type mappings you must either use these
interfaces, or the dynamic mapping interfaces above. You may not mix
usage of both for the same device. Such an act is illegal and is
guaranteed to put a banana in your tailpipe.
However, consistent mappings may in fact be used in conjunction with
these interfaces. Remember that, as defined, consistent mappings are
always going to be SAC addressable.
The first thing your driver needs to do is query the PCI platform
layer if it is capable of handling your devices DAC addressing
capabilities:
int pci_dac_dma_supported(struct pci_dev *hwdev, u64 mask);
You may not use the following interfaces if this routine fails.
Next, DMA addresses using this API are kept track of using the
dma64_addr_t type. It is guaranteed to be big enough to hold any
DAC address the platform layer will give to you from the following
routines. If you have consistent mappings as well, you still
use plain dma_addr_t to keep track of those.
All mappings obtained here will be direct. The mappings are not
translated, and this is the purpose of this dialect of the DMA API.
All routines work with page/offset pairs. This is the _ONLY_ way to
portably refer to any piece of memory. If you have a cpu pointer
(which may be validly DMA'd too) you may easily obtain the page
and offset using something like this:
struct page *page = virt_to_page(ptr);
unsigned long offset = offset_in_page(ptr);
Here are the interfaces:
dma64_addr_t pci_dac_page_to_dma(struct pci_dev *pdev,
struct page *page,
unsigned long offset,
int direction);
The DAC address for the tuple PAGE/OFFSET are returned. The direction
argument is the same as for pci_{map,unmap}_single(). The same rules
for cpu/device access apply here as for the streaming mapping
interfaces. To reiterate:
The cpu may touch the buffer before pci_dac_page_to_dma.
The device may touch the buffer after pci_dac_page_to_dma
is made, but the cpu may NOT.
When the DMA transfer is complete, invoke:
void pci_dac_dma_sync_single_for_cpu(struct pci_dev *pdev,
dma64_addr_t dma_addr,
size_t len, int direction);
This must be done before the CPU looks at the buffer again.
This interface behaves identically to pci_dma_sync_{single,sg}_for_cpu().
And likewise, if you wish to let the device get back at the buffer after
the cpu has read/written it, invoke:
void pci_dac_dma_sync_single_for_device(struct pci_dev *pdev,
dma64_addr_t dma_addr,
size_t len, int direction);
before letting the device access the DMA area again.
If you need to get back to the PAGE/OFFSET tuple from a dma64_addr_t
the following interfaces are provided:
struct page *pci_dac_dma_to_page(struct pci_dev *pdev,
dma64_addr_t dma_addr);
unsigned long pci_dac_dma_to_offset(struct pci_dev *pdev,
dma64_addr_t dma_addr);
This is possible with the DAC interfaces purely because they are
not translated in any way.
Optimizing Unmap State Space Consumption
On many platforms, pci_unmap_{single,page}() is simply a nop.