On Tue, Nov 24, 2015 at 04:06:41PM +0000, Peter Maydell wrote: > The existing device tree bindings assume that we are only trying to > describe a single address space with a device tree (for ARM, either > the Normal or the Secure world). Some uses for device tree need to > describe both Normal and Secure worlds in a single device tree. Add > documentation of how to do this, by adding extra properties which > describe when a device appears differently in the two worlds or when > it only appears in one of them. > > The binding describes the general principles for adding new > properties describing the secure world, but for now we only need a > single new property, "secure-status", which can be used to annotate > devices to indicate that they are only visible in one of the two > worlds. > > The primary expected use of this binding is for a virtual machine > like QEMU to describe the VM layout to a TrustZone aware firmware > (which would then use the secure-only devices itself, and pass the DT > on to a kernel running in the non-secure world, which ignores the > secure-only devices and uses the rest). > > Signed-off-by: Peter Maydell <peter.maydell@xxxxxxxxxx> > --- > This binding doesn't affect the kernel itself, but the kernel > Documentation/ tree is the de-facto current place where all DT > bindings are documented, so Grant suggested this was the right > place to send a doc patch. > > Changes v1->v2: > * list all the status/secure-status combinations explicitly > * use /* */ comment syntax, not // > Changes v2->v3: > * use secure-foo rather than secure-reg as the example when > explaining how the prefixing works > * say how prefixing a vendor,foo property name works Applied, thanks. Rob > > Documentation/devicetree/bindings/arm/secure.txt | 53 ++++++++++++++++++++++++ > 1 file changed, 53 insertions(+) > create mode 100644 Documentation/devicetree/bindings/arm/secure.txt > > diff --git a/Documentation/devicetree/bindings/arm/secure.txt b/Documentation/devicetree/bindings/arm/secure.txt > new file mode 100644 > index 0000000..e31303f > --- /dev/null > +++ b/Documentation/devicetree/bindings/arm/secure.txt > @@ -0,0 +1,53 @@ > +* ARM Secure world bindings > + > +ARM CPUs with TrustZone support have two distinct address spaces, > +"Normal" and "Secure". Most devicetree consumers (including the Linux > +kernel) are not TrustZone aware and run entirely in either the Normal > +world or the Secure world. However some devicetree consumers are > +TrustZone aware and need to be able to determine whether devices are > +visible only in the Secure address space, only in the Normal address > +space, or visible in both. (One example of that situation would be a > +virtual machine which boots Secure firmware and wants to tell the > +firmware about the layout of the machine via devicetree.) > + > +The general principle of the naming scheme for Secure world bindings > +is that any property that needs a different value in the Secure world > +can be supported by prefixing the property name with "secure-". So for > +instance "secure-foo" would override "foo". For property names with > +a vendor prefix, the Secure variant of "vendor,foo" would be > +"vendor,secure-foo". If there is no "secure-" property then the Secure > +world value is the same as specified for the Normal world by the > +non-prefixed property. However, only the properties listed below may > +validly have "secure-" versions; this list will be enlarged on a > +case-by-case basis. > + > +Defining the bindings in this way means that a device tree which has > +been annotated to indicate the presence of Secure-only devices can > +still be processed unmodified by existing Non-secure software (and in > +particular by the kernel). > + > +Note that it is still valid for bindings intended for purely Secure > +world consumers (like kernels that run entirely in Secure) to simply > +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: > + > +- secure-status : specifies whether the device is present and usable > + in the secure world. The combination of this with "status" allows > + the various possible combinations of device visibility to be > + specified. If "secure-status" is not specified it defaults to the > + same value as "status"; if "status" is not specified either then > + both default to "okay". This means the following combinations are > + possible: > + > + /* Neither specified: default to visible in both S and NS */ > + secure-status = "okay"; /* visible in both */ > + status = "okay"; /* visible in both */ > + status = "okay"; secure-status = "okay"; /* visible in both */ > + secure-status = "disabled"; /* NS-only */ > + status = "okay"; secure-status = "disabled"; /* NS-only */ > + status = "disabled"; secure-status = "okay"; /* S-only */ > + status = "disabled"; /* disabled in both */ > + status = "disabled"; secure-status = "disabled"; /* disabled in both */ > -- > 1.9.1 > > -- > To unsubscribe from this list: send the line "unsubscribe devicetree" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
