[PATCH v7 1/4] of: also handle dma-noncoherent in of_dma_is_coherent()

From: Heiko Stuebner
Date: Wed Jul 06 2022 - 19:15:59 EST


of_dma_is_coherent() currently expects the architecture to be
non-coherent and some devices being coherent getting marked
as such with the dma-coherent devicetree property.

For PowerPC CONFIG_OF_DMA_DEFAULT_COHERENT was added which currently
makes of_dma_is_coherent() always return true but doesn't handle
the case of the architecture being coherent but some devices not.

So modify the function to also check for dma-noncoherent and
set a suitable default return value. If CONFIG_OF_DMA_DEFAULT_COHERENT
is set the value starts with true and finding dma-noncoherent will
set it to false and without CONFIG_OF_DMA_DEFAULT_COHERENT, the
behaviour is reversed.

Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
Reviewed-by: Guo Ren <guoren@xxxxxxxxxx>
Signed-off-by: Heiko Stuebner <heiko@xxxxxxxxx>
---
drivers/of/address.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/drivers/of/address.c b/drivers/of/address.c
index 94f017d808c4..96f0a12e507c 100644
--- a/drivers/of/address.c
+++ b/drivers/of/address.c
@@ -1045,26 +1045,29 @@ phys_addr_t __init of_dma_get_max_cpu_address(struct device_node *np)
*
* It returns true if "dma-coherent" property was found
* for this device in the DT, or if DMA is coherent by
- * default for OF devices on the current platform.
+ * default for OF devices on the current platform and no
+ * "dma-noncoherent" property was found for this device.
*/
bool of_dma_is_coherent(struct device_node *np)
{
struct device_node *node;
-
- if (IS_ENABLED(CONFIG_OF_DMA_DEFAULT_COHERENT))
- return true;
+ bool is_coherent = IS_ENABLED(CONFIG_OF_DMA_DEFAULT_COHERENT);

node = of_node_get(np);

while (node) {
if (of_property_read_bool(node, "dma-coherent")) {
- of_node_put(node);
- return true;
+ is_coherent = true;
+ break;
+ }
+ if (of_property_read_bool(node, "dma-noncoherent")) {
+ is_coherent = false;
+ break;
}
node = of_get_next_dma_parent(node);
}
of_node_put(node);
- return false;
+ return is_coherent;
}
EXPORT_SYMBOL_GPL(of_dma_is_coherent);

--
2.35.1