projects / deliverable / linux.git / blame
| Commit | Line | Data |
|---|---|---|
| d9f43bab PM |
1 | * ARM Secure world bindings |
| 2 | ||
| 3 | ARM CPUs with TrustZone support have two distinct address spaces, | |
| 4 | "Normal" and "Secure". Most devicetree consumers (including the Linux | |
| 5 | kernel) are not TrustZone aware and run entirely in either the Normal | |
| 6 | world or the Secure world. However some devicetree consumers are | |
| 7 | TrustZone aware and need to be able to determine whether devices are | |
| 8 | visible only in the Secure address space, only in the Normal address | |
| 9 | space, or visible in both. (One example of that situation would be a | |
| 10 | virtual machine which boots Secure firmware and wants to tell the | |
| 11 | firmware about the layout of the machine via devicetree.) | |
| 12 | ||
| 13 | The general principle of the naming scheme for Secure world bindings | |
| 14 | is that any property that needs a different value in the Secure world | |
| 15 | can be supported by prefixing the property name with "secure-". So for | |
| 16 | instance "secure-foo" would override "foo". For property names with | |
| 17 | a vendor prefix, the Secure variant of "vendor,foo" would be | |
| 18 | "vendor,secure-foo". If there is no "secure-" property then the Secure | |
| 19 | world value is the same as specified for the Normal world by the | |
| 20 | non-prefixed property. However, only the properties listed below may | |
| 21 | validly have "secure-" versions; this list will be enlarged on a | |
| 22 | case-by-case basis. | |
| 23 | ||
| 24 | Defining the bindings in this way means that a device tree which has | |
| 25 | been annotated to indicate the presence of Secure-only devices can | |
| 26 | still be processed unmodified by existing Non-secure software (and in | |
| 27 | particular by the kernel). | |
| 28 | ||
| 29 | Note that it is still valid for bindings intended for purely Secure | |
| 30 | world consumers (like kernels that run entirely in Secure) to simply | |
| 31 | describe the view of Secure world using the standard bindings. These | |
| 32 | secure- bindings only need to be used where both the Secure and Normal | |
| 33 | world views need to be described in a single device tree. | |
| 34 | ||
| 35 | Valid Secure world properties: | |
| 36 | ||
| 37 | - secure-status : specifies whether the device is present and usable | |
| 38 | in the secure world. The combination of this with "status" allows | |
| 39 | the various possible combinations of device visibility to be | |
| 40 | specified. If "secure-status" is not specified it defaults to the | |
| 41 | same value as "status"; if "status" is not specified either then | |
| 42 | both default to "okay". This means the following combinations are | |
| 43 | possible: | |
| 44 | ||
| 45 | /* Neither specified: default to visible in both S and NS */ | |
| 46 | secure-status = "okay"; /* visible in both */ | |
| 47 | status = "okay"; /* visible in both */ | |
| 48 | status = "okay"; secure-status = "okay"; /* visible in both */ | |
| 49 | secure-status = "disabled"; /* NS-only */ | |
| 50 | status = "okay"; secure-status = "disabled"; /* NS-only */ | |
| 51 | status = "disabled"; secure-status = "okay"; /* S-only */ | |
| 52 | status = "disabled"; /* disabled in both */ | |
| 53 | status = "disabled"; secure-status = "disabled"; /* disabled in both */ |