Hi Muhammad,

On Thu, 2016-09-29 at 12:26:13 +0200, Muhammad Abdul WAHAB wrote:

The Coresight components are present on the Zynq SoC but the corresponding
device tree entries are missing. This patch adds device tree entries for
coresight components while explaining how it was done in order to allow
porting towards other boards easily.

By adding the entries for Coresight components in the device tree: if no
files are created in sysfile system, you need to contact the board designer
to sort out the problem. On some boards, Coresight components are not
powered on boot.

Signed-off-by: Muhammad Abdul Wahab <redacted>
---
The documentation file was very helpful
(Documentation/devicetree/bindings/arm/coresight.txt). However, few details
can be added to make it more clear for beginners.

Things to modify in device tree when changing the board are mainly:

- address
- `clocks` field
- some references in other entries may be missing (e.g. for `CPU` field in
  ETM/PTM component, references need to be created)

Furthermore, the `reg` field should be adapted according to
`#address-cells` and `#size-cells`. It may appear obvious, not for
beginners.

## Testing

The trace sink components need to be enabled by accessing through sysfile
system.

    echo 1 > /sys/bus/coresight/devices/@addr.etb/enable\_sink

Then enable the CS source component:

    echo 1 > /sys/bus/coresight/devices/@addr.ptm/enable\_source

By default, CS Source components are configured to trace the kernel.

Then the trace can be read by dumping ETB.

    dd if=/dev/@addr.etb of=trace_kernel.bin

The trace can be visualized by:

    hexdump -C trace_kernel.bin

Or stored using:

    hexdump -C trace_kernel.bin > trace_kernel.txt

The trace need to be decoded to be readable. All these above steps can now
be performed with Perf Library which was not available at the time I was
playing with DT entries.

I'm curious, did you test that with external debug tools. I have the
feeling the kernel using the debug HW could interfere with JTAG
debuggers, external trace tools, etc.

Use labels please.

+                    linux,phandle = <0xd>;
+                    phandle = <0xd>;

Do these phandle properties need to be here?

+                };
+            };
+        };
+
+        tpiu@F8803000 {
+            compatible = "arm,coresight-tpiu", "arm,primecell";
+            reg = <0xf8803000 0x1000>;
+            clocks = <&clkc 47>, <&clkc 16>;

I'm not sure this is correct for every setup. Sorry, that I don't recall
all the details, I haven't used tracing in a long time. But I guess this
clock is configurable as you're referring an fclk here. The other thing
that makes me a little suspicious is, that nothing in here uses the
'dbg_trc' clock that the clock controller provides.

+            clock-names = "apb_pclk", "fclk1";

Those names (at least fclk1) is not a good name for tpiu to identify
it's input. fclk1 is a zynq-specific clock, and as mentioned above, it
seems likely that this could easily become a different one. The
clock-names are meant to identify an input from the consumer's
perspective. The correct names should be documented in the DT binding.

+            clock-frequency=<0xee6b280>;

I cannot find this property in the binding.

+
+            port {
+
+                endpoint@0 {
+                    slave-mode;
+                    remote-endpoint = <0x9>;
+                    linux,phandle = <0xe>;
+                    phandle = <0xe>;
+                };
+            };
+        };
+
+        funnel@F8804000 {
+            compatible = "arm,coresight-funnel", "arm,primecell";
+            reg = <0xf8804000 0x1000>;
+            clocks = <&clkc 47>;
+            clock-names = "apb_pclk";
+
+            ports {
+                #address-cells = <0x1>;
+                #size-cells = <0x0>;
+
+                port@0 {
+                    reg = <0x0>;
+
+                    endpoint {
+                        remote-endpoint = <0xa>;
+                        linux,phandle = <0xf>;
+                        phandle = <0xf>;
+                    };
+                };
+
+                port@1 {
+                    reg = <0x0>;
+
+                    endpoint {
+                        slave-mode;
+                        remote-endpoint = <0xb>;
+                        linux,phandle = <0x11>;
+                        phandle = <0x11>;
+                    };
+                };
+
+                port@2 {
+                    reg = <0x1>;
+
+                    endpoint {
+                        slave-mode;
+                        remote-endpoint = <0xc>;
+                        linux,phandle = <0x13>;
+                        phandle = <0x13>;
+                    };
+                };
+            };
+        };
+
+        replicator {
+            compatible = "arm,coresight-replicator";
+
+            ports {
+                #address-cells = <0x1>;
+                #size-cells = <0x0>;
+
+                port@0 {
+                    reg = <0x0>;
+
+                    endpoint {
+                        remote-endpoint = <0xd>;
+                        linux,phandle = <0x8>;
+                        phandle = <0x8>;
+                    };
+                };
+
+                port@1 {
+                    reg = <0x1>;
+
+                    endpoint {
+                        remote-endpoint = <0xe>;
+                        linux,phandle = <0x9>;
+                        phandle = <0x9>;
+                    };
+                };
+
+                port@2 {
+                    reg = <0x0>;
+
+                    endpoint {
+                        slave-mode;
+                        remote-endpoint = <0xf>;
+                        linux,phandle = <0xa>;
+                        phandle = <0xa>;
+                    };
+                };
+            };
+        };
+
+        ptm0@F889C000 {
+            compatible = "arm,coresight-etm3x", "arm,primecell";
+            reg = <0xf889c000 0x1000>;
+            cpu = <0x10>;
+            clocks = <&clkc 47>;
+            clock-names = "apb_pclk";
+
+            port {
+
+                endpoint {
+                    remote-endpoint = <0x11>;
+                    linux,phandle = <0xb>;
+                    phandle = <0xb>;
+                };
+            };
+        };
+
+        ptm1@F889D000 {
+            compatible = "arm,coresight-etm3x", "arm,primecell";
+            reg = <0xf889d000 0x1000>;
+            cpu = <0x12>;
+            clocks = <&clkc 47>;
+            clock-names = "apb_pclk";
+
+            port {
+
+                endpoint {
+                    remote-endpoint = <0x13>;
+                    linux,phandle = <0xc>;
+                    phandle = <0xc>;
+                };
+            };
+        };
     };
 };

I think nodes were ordered alphabetically in our DTs.

	Sören

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