[PATCH 5.5 138/367] of: Add OF_DMA_DEFAULT_COHERENT & select it on powerpc

Greg Kroah-Hartman
2020-02-10T13:03:57Z

From: Michael Ellerman <mpe@ellerman.id.au>

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>

---
arch/powerpc/Kconfig | 1 +
drivers/of/Kconfig | 4 ++++
drivers/of/address.c | 6 +++++-
3 files changed, 10 insertions(+), 1 deletion(-)

--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -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
--- a/drivers/of/Kconfig
+++ b/drivers/of/Kconfig
@@ -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
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -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);