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of: Add OF_DMA_DEFAULT_COHERENT & select it on powerpc

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commit dabf6b36b83a18d57e3d4b9d50544ed040d86255 upstream.

There's an OF helper called of_dma_is_coherent(), which checks if a
device has a "dma-coherent" property to see if the device is coherent
for DMA.

But on some platforms devices are coherent by default, and on some
platforms it's not possible to update existing device trees to add the
"dma-coherent" property.

So add a Kconfig symbol to allow arch code to tell
of_dma_is_coherent() that devices are coherent by default, regardless
of the presence of the property.

Select that symbol on powerpc when NOT_COHERENT_CACHE is not set, ie.
when the system has a coherent cache.

Fixes: 92ea637ede ("of: introduce of_dma_is_coherent() helper")
Cc: [email protected] # v3.16+
Reported-by: Christian Zigotzky <[email protected]>
Tested-by: Christian Zigotzky <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Reviewed-by: Ulf Hansson <[email protected]>
Signed-off-by: Rob Herring <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
This commit is contained in:
Michael Ellerman 2020-01-26 22:52:47 +11:00 • committed by Greg Kroah-Hartman
commit bae74e7ac8
3 changed files with 10 additions and 1 deletions
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4
drivers/of/Kconfig
View file

@ -103,4 +103,8 @@ config OF_OVERLAY
config OF_NUMA
bool
config OF_DMA_DEFAULT_COHERENT
# arches should select this if DMA is coherent by default for OF devices
bool
endif # OF

6
drivers/of/address.c
View file

@ -998,12 +998,16 @@ EXPORT_SYMBOL_GPL(of_dma_get_range);
* @np: device node
*
* It returns true if "dma-coherent" property was found
* for this device in DT.
* for this device in the DT, or if DMA is coherent by
* default for OF devices on the current platform.
*/
bool of_dma_is_coherent(struct device_node *np)
{
struct device_node *node = of_node_get(np);
if (IS_ENABLED(CONFIG_OF_DMA_DEFAULT_COHERENT))
return true;
while (node) {
if (of_property_read_bool(node, "dma-coherent")) {
of_node_put(node);