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of: Add OF_DMA_DEFAULT_COHERENT & select it on powerpc

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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: stable@vger.kernel.org # v3.16+
Reported-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Tested-by: Christian Zigotzky <chzigotzky@xenosoft.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Reviewed-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Rob Herring <robh@kernel.org>
This commit is contained in:
Michael Ellerman 2020-01-26 22:52:47 +11:00 committed by Rob Herring
parent 9243f29691
commit dabf6b36b8
3 changed files with 10 additions and 1 deletions
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1
arch/powerpc/Kconfig
View File

@ -238,6 +238,7 @@ config PPC
select NEED_DMA_MAP_STATE if PPC64 || NOT_COHERENT_CACHE
select NEED_SG_DMA_LENGTH
select OF
select OF_DMA_DEFAULT_COHERENT if !NOT_COHERENT_CACHE
select OF_EARLY_FLATTREE
select OLD_SIGACTION if PPC32
select OLD_SIGSUSPEND

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

@ -995,12 +995,16 @@ out:
* @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);