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[RFC,3/5] dt-bindings: gpu: Add protected heap name to Mali Valhall CSF binding

Message ID 36b57dcf20860398ba83985e1c5b6f6958d08ba7.1738228114.git.florent.tomasin@arm.com
State New
Headers show
Series [RFC,1/5] dt-bindings: dma: Add CMA Heap bindings | expand

Commit Message

Florent Tomasin Jan. 30, 2025, 1:08 p.m. UTC 
Allow mali-valhall-csf driver to retrieve a protected
heap at probe time by passing the name of the heap
as attribute to the device tree GPU node.

Signed-off-by: Florent Tomasin <florent.tomasin@arm.com>
---
 .../devicetree/bindings/gpu/arm,mali-valhall-csf.yaml       | 6 ++++++
 1 file changed, 6 insertions(+)

Comments

Florent Tomasin Feb. 3, 2025, 3:31 p.m. UTC | #1 
Hi Krzysztof

On 30/01/2025 13:25, Krzysztof Kozlowski wrote:
> On 30/01/2025 14:08, Florent Tomasin wrote:
>> Allow mali-valhall-csf driver to retrieve a protected
>> heap at probe time by passing the name of the heap
>> as attribute to the device tree GPU node.
> 
> Please wrap commit message according to Linux coding style / submission
> process (neither too early nor over the limit):
> https://elixir.bootlin.com/linux/v6.4-rc1/source/Documentation/process/submitting-patches.rst#L597
Apologies, I think I made quite few other mistakes in the style of the
patches I sent. I will work on improving this aspect, appreciated

> Why this cannot be passed by phandle, just like all reserved regions?
> 
> From where do you take these protected heaps? Firmware? This would
> explain why no relation is here (no probe ordering, no device links,
> nothing connecting separate devices).

The protected heap is generaly obtained from a firmware (TEE) and could
sometimes be a carved-out memory with restricted access.

The Panthor CSF kernel driver does not own or manage the protected heap
and is instead a consumer of it (assuming the heap is made available by
the system integrator).

I initially used a phandle, but then I realised it would introduce a new
API to share the heap across kernel driver. In addition I found this
patch series:
-
https://lore.kernel.org/lkml/20230911023038.30649-1-yong.wu@mediatek.com/#t

which introduces a DMA Heap API to the rest of the kernel to find a
heap by name:
- dma_heap_find()

I then decided to follow that approach to help isolate the heap
management from the GPU driver code. In the Panthor driver, if the
heap is not found at probe time, the driver will defer the probe until
the exporter made it available.

Best regards,
Florent
diff mbox series

Patch

diff --git a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
index a5b4e0021758..dc633b037ede 100644
--- a/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
+++ b/Documentation/devicetree/bindings/gpu/arm,mali-valhall-csf.yaml
@@ -85,6 +85,12 @@  properties:
 
   dma-coherent: true
 
+  protected-heap-name:
+    $ref: /schemas/types.yaml#/definitions/string
+    description:
+      Specifies the name of the protected Heap from
+      which the GPU driver allocates protected memory.
+
 required:
   - compatible
   - reg