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

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Date:   Fri, 16 Jun 2023 08:14:38 -0700
From:   Douglas Anderson <dianders@...omium.org>
To:     andersson@...nel.org
Cc:     amit.pundir@...aro.org, Will Deacon <will@...nel.org>,
        sumit.semwal@...aro.org, linux-arm-msm@...r.kernel.org,
        konrad.dybcio@...ainline.org, linux-arm-kernel@...ts.infradead.org,
        Stephan Gerhold <stephan@...hold.net>,
        Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Nikita Travkin <nikita@...n.ru>,
        Stephen Boyd <swboyd@...omium.org>,
        Sibi Sankar <quic_sibis@...cinc.com>,
        Douglas Anderson <dianders@...omium.org>,
        Andy Gross <agross@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Das Srinagesh <quic_gurus@...cinc.com>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Robert Marko <robimarko@...il.com>, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/4] dt-bindings: firmware: qcom,scm: Document that SCM can be dma-coherent

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@...omium.org>
---

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