On 12/09/2023 9:28 am, Krzysztof Kozlowski wrote:
On 12/09/2023 08:16, Yong Wu (吴勇) wrote:
Hi Rob,
Thanks for your review.
On Mon, 2023-09-11 at 10:44 -0500, Rob Herring wrote:
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On Mon, Sep 11, 2023 at 10:30:37AM +0800, Yong Wu wrote:
This adds the binding for describing a CMA memory for MediaTek
SVP(Secure
Video Path).
CMA is a Linux thing. How is this related to CMA?
Signed-off-by: Yong Wu <yong.wu@xxxxxxxxxxxx>
---
.../mediatek,secure_cma_chunkmem.yaml | 42
+++++++++++++++++++
1 file changed, 42 insertions(+)
create mode 100644 Documentation/devicetree/bindings/reserved-
memory/mediatek,secure_cma_chunkmem.yaml
diff --git a/Documentation/devicetree/bindings/reserved-
memory/mediatek,secure_cma_chunkmem.yaml
b/Documentation/devicetree/bindings/reserved-
memory/mediatek,secure_cma_chunkmem.yaml
new file mode 100644
index 000000000000..cc10e00d35c4
--- /dev/null
+++ b/Documentation/devicetree/bindings/reserved-
memory/mediatek,secure_cma_chunkmem.yaml
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+%YAML 1.2
+---
+$id:
http://devicetree.org/schemas/reserved-memory/mediatek,secure_cma_chunkmem.yaml#
+$schema: http://devicetree.org/meta-schemas/core.yaml#
+
+title: MediaTek Secure Video Path Reserved Memory
What makes this specific to Mediatek? Secure video path is fairly
common, right?
Here we just reserve a buffer and would like to create a dma-buf secure
heap for SVP, then the secure engines(Vcodec and DRM) could prepare
secure buffer through it.
But the heap driver is pure SW driver, it is not platform device and
All drivers are pure SW.
we don't have a corresponding HW unit for it. Thus I don't think I
could create a platform dtsi node and use "memory-region" pointer to
the region. I used RESERVEDMEM_OF_DECLARE currently(The code is in
[9/9]). Sorry if this is not right.
If this is not for any hardware and you already understand this (since
you cannot use other bindings) then you cannot have custom bindings for
it either.
Then in our usage case, is there some similar method to do this? or
any other suggestion?
Don't stuff software into DTS.
Aren't most reserved-memory bindings just software policy if you look at
it that way, though? IIUC this is a pool of memory that is visible and
available to the Non-Secure OS, but is fundamentally owned by the Secure
TEE, and pages that the TEE allocates from it will become physically
inaccessible to the OS. Thus the platform does impose constraints on how
the Non-Secure OS may use it, and per the rest of the reserved-memory
bindings, describing it as a "reusable" reservation seems entirely
appropriate. If anything that's *more* platform-related and so
DT-relevant than typical arbitrary reservations which just represent
"save some memory to dedicate to a particular driver" and don't actually
bear any relationship to firmware or hardware at all.
However, the fact that Linux's implementation of how to reuse reserved
memory areas is called CMA is indeed still irrelevant and has no place
in the binding itself.
Thanks,
Robin.
