Commit 3ad96787 authored Sep 20, 2023 by Bjorn Andersson Committed by Bjorn Andersson Sep 27, 2023

dt-bindings: reserved-memory: rmtfs: Allow guard pages

On some Qualcomm platforms the firwmare, or hardware, does not
gracefully handle memory protection of the rmtfs memory region when
placed adjacent to other protected region. Some DeviceTree authors have
worked around this issue by explicitly reserving the space around the
region, but this prevents such author to use rely on the OS to place the
region, through the use of "size" (instead of a fixed location).

Introduce a flag to indicate that guard pages need be carved at the
beginning and end of the memory region. The user shall account for the
two pages in the defined size.

Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230920-rmtfs-mem-guard-pages-v3-1-305b37219b78@quicinc.com

Signed-off-by: Bjorn Andersson <andersson@kernel.org>

parent f6aa7386

Documentation/devicetree/bindings/reserved-memory/qcom,rmtfs-mem.yaml

+11 −0

Original line number	Diff line number	Diff line
		@@ -26,6 +26,17 @@ properties:
		description: >
		identifier of the client to use this region for buffers

		qcom,use-guard-pages:
		type: boolean
		description: >
		Indicates that the firmware, or hardware, does not gracefully handle
		memory protection of this region when placed adjacent to other protected
		memory regions, and that padding around the used portion of the memory
		region is necessary.

		When this is set, the first and last page should be left unused, and the
		effective size of the region will thereby shrink with two pages.

		qcom,vmid:
		$ref: /schemas/types.yaml#/definitions/uint32-array
		description: >