Some platforms may use a single device tree to describe two address spaces, as described in d9f43babb998 ("Documentation: dt: Add bindings for Secure-only devices"). For these platforms it makes sense to define a secure counterpart of /chosen, namely: /secure-chosen. This new node is meant to be used by the secure firmware to pass data to the secure OS. Only the stdout-path property is supported for now.

Signed-off-by: Jerome Forissier jerome.forissier@linaro.org ---

Notes: Sending this again, slightly modified. Previous submission was in March 2017 [1]. Since then, OP-TEE has implemented this binding for platforms that use DT [2] (fallback to /chosen/stdout-path to be implemented in [3]). A patch for QEMU has been proposed [4], to which the maintainer responded "Are the DT bindings upstream yet?" ;-)

[1] https://patchwork.kernel.org/patch/9602401/ [2] https://github.com/OP-TEE/optee_os/commit/4dc31c52544a [3] https://github.com/OP-TEE/optee_os/pull/2569 [4] https://patchwork.ozlabs.org/patch/979345/

Changes since v1: - Use "should" instead of "may" ("...the Secure OS should use the value of /chosen/stdout-path...").

Documentation/devicetree/bindings/arm/secure.txt | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/Documentation/devicetree/bindings/arm/secure.txt b/Documentation/devicetree/bindings/arm/secure.txt index e31303fb233a..f27bbff2c780 100644 --- a/Documentation/devicetree/bindings/arm/secure.txt +++ b/Documentation/devicetree/bindings/arm/secure.txt @@ -32,7 +32,8 @@ describe the view of Secure world using the standard bindings. These secure- bindings only need to be used where both the Secure and Normal world views need to be described in a single device tree.

-Valid Secure world properties: +Valid Secure world properties +-----------------------------

- secure-status : specifies whether the device is present and usable in the secure world. The combination of this with "status" allows @@ -51,3 +52,19 @@ Valid Secure world properties: status = "disabled"; secure-status = "okay"; /* S-only */ status = "disabled"; /* disabled in both */ status = "disabled"; secure-status = "disabled"; /* disabled in both */ + +The secure-chosen node +---------------------- + +Similar to the /chosen node which serves as a place for passing data +between firmware and the operating system, the /secure-chosen node may +be used to pass data to the Secure OS. Only the properties defined +below may appear in the /secure-chosen node. + +- stdout-path : specifies the device to be used by the Secure OS for + its console output. The syntax is the same as for /chosen/stdout-path. + If the /secure-chosen node exists but the stdout-path property is not + present, the Secure OS should not perform any console output. If + /secure-chosen does not exist, the Secure OS should use the value of + /chosen/stdout-path instead (that is, use the same device as the + Normal world OS).