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authorLinus Torvalds <torvalds@linux-foundation.org>2013-05-09 09:46:45 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2013-05-09 09:46:45 -0700
commit1763e735b0a093a6747078b3bd101f079e576ab6 (patch)
tree75203a3229977d12dc5a5990d1122e7a3d5f30fc /Documentation/acpi
parentb29bdba51924f6fd5971352ba111784dee3a5853 (diff)
parent3065c194670b61e213656ce25976d7c8a95e3c93 (diff)
downloadkernel-1763e735b0a093a6747078b3bd101f079e576ab6.tar.gz
Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma
Pull slave-dmaengine updates from Vinod Koul: "This time we have dmatest improvements from Andy along with dw_dmac fixes. He has also done support for acpi for dmanegine. Also we have bunch of fixes going in DT support for dmanegine for various folks. Then Haswell and other ioat changes from Dave and SUDMAC support from Shimoda." * 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma: (53 commits) dma: tegra: implement suspend/resume callbacks dma:of: Use a mutex to protect the of_dma_list dma: of: Fix of_node reference leak dmaengine: sirf: move driver init from module_init to subsys_initcall sudmac: add support for SUDMAC dma: sh: add Kconfig at_hdmac: move to generic DMA binding ioatdma: ioat3_alloc_sed can be static ioatdma: Adding write back descriptor error status support for ioatdma 3.3 ioatdma: S1200 platforms ioatdma channel 2 and 3 falsely advertise RAID cap ioatdma: Adding support for 16 src PQ ops and super extended descriptors ioatdma: Removing hw bug workaround for CB3.x .2 and earlier dw_dmac: add ACPI support dmaengine: call acpi_dma_request_slave_channel as well dma: acpi-dma: introduce ACPI DMA helpers dma: of: Remove unnecessary list_empty check DMA: OF: Check properties value before running be32_to_cpup() on it DMA: of: Constant names ioatdma: skip silicon bug workaround for pq_align for cb3.3 ioatdma: Removing PQ val disable for cb3.3 ...
Diffstat (limited to 'Documentation/acpi')
-rw-r--r--Documentation/acpi/enumeration.txt77
1 files changed, 77 insertions, 0 deletions
diff --git a/Documentation/acpi/enumeration.txt b/Documentation/acpi/enumeration.txt
index b0d541042ac6..d9be7a97dff3 100644
--- a/Documentation/acpi/enumeration.txt
+++ b/Documentation/acpi/enumeration.txt
@@ -66,6 +66,83 @@ the ACPI device explicitly to acpi_platform_device_ids list defined in
drivers/acpi/acpi_platform.c. This limitation is only for the platform
devices, SPI and I2C devices are created automatically as described below.
+DMA support
+~~~~~~~~~~~
+DMA controllers enumerated via ACPI should be registered in the system to
+provide generic access to their resources. For example, a driver that would
+like to be accessible to slave devices via generic API call
+dma_request_slave_channel() must register itself at the end of the probe
+function like this:
+
+ err = devm_acpi_dma_controller_register(dev, xlate_func, dw);
+ /* Handle the error if it's not a case of !CONFIG_ACPI */
+
+and implement custom xlate function if needed (usually acpi_dma_simple_xlate()
+is enough) which converts the FixedDMA resource provided by struct
+acpi_dma_spec into the corresponding DMA channel. A piece of code for that case
+could look like:
+
+ #ifdef CONFIG_ACPI
+ struct filter_args {
+ /* Provide necessary information for the filter_func */
+ ...
+ };
+
+ static bool filter_func(struct dma_chan *chan, void *param)
+ {
+ /* Choose the proper channel */
+ ...
+ }
+
+ static struct dma_chan *xlate_func(struct acpi_dma_spec *dma_spec,
+ struct acpi_dma *adma)
+ {
+ dma_cap_mask_t cap;
+ struct filter_args args;
+
+ /* Prepare arguments for filter_func */
+ ...
+ return dma_request_channel(cap, filter_func, &args);
+ }
+ #else
+ static struct dma_chan *xlate_func(struct acpi_dma_spec *dma_spec,
+ struct acpi_dma *adma)
+ {
+ return NULL;
+ }
+ #endif
+
+dma_request_slave_channel() will call xlate_func() for each registered DMA
+controller. In the xlate function the proper channel must be chosen based on
+information in struct acpi_dma_spec and the properties of the controller
+provided by struct acpi_dma.
+
+Clients must call dma_request_slave_channel() with the string parameter that
+corresponds to a specific FixedDMA resource. By default "tx" means the first
+entry of the FixedDMA resource array, "rx" means the second entry. The table
+below shows a layout:
+
+ Device (I2C0)
+ {
+ ...
+ Method (_CRS, 0, NotSerialized)
+ {
+ Name (DBUF, ResourceTemplate ()
+ {
+ FixedDMA (0x0018, 0x0004, Width32bit, _Y48)
+ FixedDMA (0x0019, 0x0005, Width32bit, )
+ })
+ ...
+ }
+ }
+
+So, the FixedDMA with request line 0x0018 is "tx" and next one is "rx" in
+this example.
+
+In robust cases the client unfortunately needs to call
+acpi_dma_request_slave_chan_by_index() directly and therefore choose the
+specific FixedDMA resource by its index.
+
SPI serial bus support
~~~~~~~~~~~~~~~~~~~~~~
Slave devices behind SPI bus have SpiSerialBus resource attached to them.