On Thu, May 5, 2016 at 9:39 AM, Jon Hunter [off-list ref] wrote:

On 03/05/16 19:22, Rob Herring wrote:

quoted

On Fri, Apr 29, 2016 at 02:53:45PM +0100, Jon Hunter wrote:

quoted

Add binding documentation for the Tegra ACONNECT bus that is part of the
Audio Processing Engine (APE) on Tegra210. The ACONNECT bus is used to
access devices within the APE subsystem. The APE is located in a
separate power domain and so accesses made to the ACONNECT require the
power domain to be enabled as well as some platform specific clocks.

Signed-off-by: Jon Hunter <redacted>
---
 .../bindings/bus/nvidia,tegra210-aconnect.txt      | 45 ++++++++++++++++++++++
 1 file changed, 45 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt

diff --git a/Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt b/Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt
new file mode 100644
index 000000000000..e5e915f8fca7
--- /dev/null
+++ b/Documentation/devicetree/bindings/bus/nvidia,tegra210-aconnect.txt

@@ -0,0 +1,45 @@
+NVIDIA Tegra ACONNECT Bus
+
+The Tegra ACONNECT bus is an AXI switch which is used to connnect various
+components inside the Audio Processing Engine (APE). All CPU accesses to
+the APE subsystem go through the ACONNECT via an APB to AXI wrapper.
+
+Required properties:
+- compatible: Must be "nvidia,tegra210-aconnect".
+- clocks: Must contain the entries for the APE clock (TEGRA210_CLK_APE),
+  and APE interface clock (TEGRA210_CLK_APB2APE).
+- clock-names: Must contain the names "ape" and "apb2ape" for the corresponding
+  'clocks' entries.
+- power-domains: Must contain a phandle that points to the audio powergate
+  (namely 'aud') for Tegra210.
+- #address-cells: The number of cells used to represent physical base addresses
+  in the host1x address space. Should be 2.
+- #size-cells: The number of cells used to represent the size of an address
+  range in the host1x address space. Should be 2.

Do you really need >4GB of child addresses?

Sounds rather silly when you put it like that. No, its not needed. I
will fix that.

quoted

quoted

+- ranges: 1:1 mapping of the aconnect address space to the CPU address space.

Why 1:1 for 256KB of address space?

No good reason. I have looking at what we did for host1x and ahub which
also have a ranges property and use a 1:1 mapping. For ahub this makes
sense because it is more of a cross-bar/switch. The aconnect bus is also
a switch and thought may be that is the easiest thing to do. What is
recommended here?

Use of non-empty ranges is preferred though there is not much benefit
if the parent and child sizes are the same. However, it does also
limit what is a valid address for those child nodes.

Rob