[PATCH v2 1/4] dt-bindings: firmware: qcom,scm: Document that SCM can be dma-coherent

[Douglas Anderson]

Trogdor devices use firmware backed by TF-A instead of Qualcomm's
normal TZ. On TF-A we end up mapping memory as cacheable. Specifically,
you can see in Trogdor's TF-A code [1] in qti_sip_mem_assign() that we
call qti_mmap_add_dynamic_region() with MT_RO_DATA. This translates
down to MT_MEMORY instead of MT_NON_CACHEABLE or MT_DEVICE.

Let's allow devices like trogdor to be described properly by allowing
"dma-coherent" in the SCM node.

Signed-off-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
---

Changes in v2:
- Bindings change new for v2.

 Documentation/devicetree/bindings/firmware/qcom,scm.yaml | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/Documentation/devicetree/bindings/firmware/qcom,scm.yaml b/Documentation/devicetree/bindings/firmware/qcom,scm.yaml
index 367d04ad1923..83381f3a1341 100644
--- a/Documentation/devicetree/bindings/firmware/qcom,scm.yaml
+++ b/Documentation/devicetree/bindings/firmware/qcom,scm.yaml
@@ -71,6 +71,8 @@ properties:
     minItems: 1
     maxItems: 3
 
+  dma-coherent: true
+
   interconnects:
     maxItems: 1
 
-- 
2.41.0.162.gfafddb0af9-goog