of: Add OF_DMA_DEFAULT_COHERENT & select it on powerpc

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: 92ea637edea3 ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index fa8f2aa8818928ce10d6e7c36c297d679d7bb4f9..f529d3d9d88d7315bc53c83f3cdd9884f38c7120 100644 (file)
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -85,6 +85,7 @@ config PPC
        select BINFMT_ELF
        select ARCH_HAS_ELF_RANDOMIZE
        select OF
+       select OF_DMA_DEFAULT_COHERENT          if !NOT_COHERENT_CACHE
        select OF_EARLY_FLATTREE
        select OF_RESERVED_MEM
        select HAVE_FTRACE_MCOUNT_RECORD

diff --git a/drivers/of/Kconfig b/drivers/of/Kconfig
index ba7b034b2b91c94afb1b7135cdee7fc3d6955828..6b8646db110c533af3482c5e6b1a6d9bff70e6db 100644 (file)
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -112,4 +112,8 @@ 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

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 72914cdfce2a18c4245fadb338ecd12683b88a40..37619bb2c97ad9ac67c13ad67e749cfb678e8423 100644 (file)
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -896,12 +896,16 @@ 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);