aboutsummaryrefslogtreecommitdiff
path: root/Documentation
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2013-11-14 07:55:21 +0900
committerLinus Torvalds <torvalds@linux-foundation.org>2013-11-14 07:55:21 +0900
commit8ceafbfa91ffbdbb2afaea5c24ccb519ffb8b587 (patch)
tree98c9ea93362536f1ddd73175b13b7847583350df /Documentation
parent42a2d923cc349583ebf6fdd52a7d35e1c2f7e6bd (diff)
parent26ba47b18318abe7dadbe9294a611c0e932651d8 (diff)
Merge branch 'for-linus-dma-masks' of git://git.linaro.org/people/rmk/linux-arm
Pull DMA mask updates from Russell King: "This series cleans up the handling of DMA masks in a lot of drivers, fixing some bugs as we go. Some of the more serious errors include: - drivers which only set their coherent DMA mask if the attempt to set the streaming mask fails. - drivers which test for a NULL dma mask pointer, and then set the dma mask pointer to a location in their module .data section - which will cause problems if the module is reloaded. To counter these, I have introduced two helper functions: - dma_set_mask_and_coherent() takes care of setting both the streaming and coherent masks at the same time, with the correct error handling as specified by the API. - dma_coerce_mask_and_coherent() which resolves the problem of drivers forcefully setting DMA masks. This is more a marker for future work to further clean these locations up - the code which creates the devices really should be initialising these, but to fix that in one go along with this change could potentially be very disruptive. The last thing this series does is prise away some of Linux's addition to "DMA addresses are physical addresses and RAM always starts at zero". We have ARM LPAE systems where all system memory is above 4GB physical, hence having DMA masks interpreted by (eg) the block layers as describing physical addresses in the range 0..DMAMASK fails on these platforms. Santosh Shilimkar addresses this in this series; the patches were copied to the appropriate people multiple times but were ignored. Fixing this also gets rid of some ARM weirdness in the setup of the max*pfn variables, and brings ARM into line with every other Linux architecture as far as those go" * 'for-linus-dma-masks' of git://git.linaro.org/people/rmk/linux-arm: (52 commits) ARM: 7805/1: mm: change max*pfn to include the physical offset of memory ARM: 7797/1: mmc: Use dma_max_pfn(dev) helper for bounce_limit calculations ARM: 7796/1: scsi: Use dma_max_pfn(dev) helper for bounce_limit calculations ARM: 7795/1: mm: dma-mapping: Add dma_max_pfn(dev) helper function ARM: 7794/1: block: Rename parameter dma_mask to max_addr for blk_queue_bounce_limit() ARM: DMA-API: better handing of DMA masks for coherent allocations ARM: 7857/1: dma: imx-sdma: setup dma mask DMA-API: firmware/google/gsmi.c: avoid direct access to DMA masks DMA-API: dcdbas: update DMA mask handing DMA-API: dma: edma.c: no need to explicitly initialize DMA masks DMA-API: usb: musb: use platform_device_register_full() to avoid directly messing with dma masks DMA-API: crypto: remove last references to 'static struct device *dev' DMA-API: crypto: fix ixp4xx crypto platform device support DMA-API: others: use dma_set_coherent_mask() DMA-API: staging: use dma_set_coherent_mask() DMA-API: usb: use new dma_coerce_mask_and_coherent() DMA-API: usb: use dma_set_coherent_mask() DMA-API: parport: parport_pc.c: use dma_coerce_mask_and_coherent() DMA-API: net: octeon: use dma_coerce_mask_and_coherent() DMA-API: net: nxp/lpc_eth: use dma_coerce_mask_and_coherent() ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/DMA-API-HOWTO.txt37
-rw-r--r--Documentation/DMA-API.txt8
2 files changed, 30 insertions, 15 deletions
diff --git a/Documentation/DMA-API-HOWTO.txt b/Documentation/DMA-API-HOWTO.txt
index 14129f149a7..5e983031cc1 100644
--- a/Documentation/DMA-API-HOWTO.txt
+++ b/Documentation/DMA-API-HOWTO.txt
@@ -101,14 +101,23 @@ style to do this even if your device holds the default setting,
because this shows that you did think about these issues wrt. your
device.
-The query is performed via a call to dma_set_mask():
+The query is performed via a call to dma_set_mask_and_coherent():
- int dma_set_mask(struct device *dev, u64 mask);
+ int dma_set_mask_and_coherent(struct device *dev, u64 mask);
-The query for consistent allocations is performed via a call to
-dma_set_coherent_mask():
+which will query the mask for both streaming and coherent APIs together.
+If you have some special requirements, then the following two separate
+queries can be used instead:
- int dma_set_coherent_mask(struct device *dev, u64 mask);
+ The query for streaming mappings is performed via a call to
+ dma_set_mask():
+
+ int dma_set_mask(struct device *dev, u64 mask);
+
+ The query for consistent allocations is performed via a call
+ to dma_set_coherent_mask():
+
+ int dma_set_coherent_mask(struct device *dev, u64 mask);
Here, dev is a pointer to the device struct of your device, and mask
is a bit mask describing which bits of an address your device
@@ -137,7 +146,7 @@ exactly why.
The standard 32-bit addressing device would do something like this:
- if (dma_set_mask(dev, DMA_BIT_MASK(32))) {
+ if (dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))) {
printk(KERN_WARNING
"mydev: No suitable DMA available.\n");
goto ignore_this_device;
@@ -171,22 +180,20 @@ the case would look like this:
int using_dac, consistent_using_dac;
- if (!dma_set_mask(dev, DMA_BIT_MASK(64))) {
+ if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(64))) {
using_dac = 1;
consistent_using_dac = 1;
- dma_set_coherent_mask(dev, DMA_BIT_MASK(64));
- } else if (!dma_set_mask(dev, DMA_BIT_MASK(32))) {
+ } else if (!dma_set_mask_and_coherent(dev, DMA_BIT_MASK(32))) {
using_dac = 0;
consistent_using_dac = 0;
- dma_set_coherent_mask(dev, DMA_BIT_MASK(32));
} else {
printk(KERN_WARNING
"mydev: No suitable DMA available.\n");
goto ignore_this_device;
}
-dma_set_coherent_mask() will always be able to set the same or a
-smaller mask as dma_set_mask(). However for the rare case that a
+The coherent coherent mask will always be able to set the same or a
+smaller mask as the streaming mask. However for the rare case that a
device driver only uses consistent allocations, one would have to
check the return value from dma_set_coherent_mask().
@@ -199,9 +206,9 @@ address you might do something like:
goto ignore_this_device;
}
-When dma_set_mask() is successful, and returns zero, the kernel saves
-away this mask you have provided. The kernel will use this
-information later when you make DMA mappings.
+When dma_set_mask() or dma_set_mask_and_coherent() is successful, and
+returns zero, the kernel saves away this mask you have provided. The
+kernel will use this information later when you make DMA mappings.
There is a case which we are aware of at this time, which is worth
mentioning in this documentation. If your device supports multiple
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt
index 78a6c569d20..e865279cec5 100644
--- a/Documentation/DMA-API.txt
+++ b/Documentation/DMA-API.txt
@@ -142,6 +142,14 @@ internal API for use by the platform than an external API for use by
driver writers.
int
+dma_set_mask_and_coherent(struct device *dev, u64 mask)
+
+Checks to see if the mask is possible and updates the device
+streaming and coherent DMA mask parameters if it is.
+
+Returns: 0 if successful and a negative error if not.
+
+int
dma_set_mask(struct device *dev, u64 mask)
Checks to see if the mask is possible and updates the device