Changes between Initial Version and Version 1 of Arch/Soclib/Xicu

Timestamp:

Feb 16, 2010, 10:57:30 AM (15 years ago)

Author:

Nicolas Pouillon

Comment:

--

Arch/Soclib/Xicu

@@ +1 @@
+= Xicu component in Flattened device trees =
+
+[soclib:wiki:Component/VciXicu Xicu] is a m->n irq router.
+
+It concentrates 3 types of interrupt sources:
+ * IPIs (WTI)
+ * Timers (PTI)
+ * External IRQ lines (HWI)
+
+These inputs can be filtered independently for each output signal.
+
+= MutekH context =
+
+In MutekH, we preferably use the Xicu with:
+ * N IPIs: 1 per processor
+ * 1 timer
+ * M Input IRQ lines (as needed)
+ * N output lines: 1 per processor
+
+== MutekH device tree representation ==
+
+In MutekH device tree, Xicu is quite tricky to reprensent; we can enumerate the following logical devices:
+ * a (multi) timer
+ * 1 ICU (with input selection, masking and callbacks) per CPU.
+
+Thus we use the following device tree:
+
+ * Xicu root (a timer)
+   * Xicu filter for output 0
+   * Xicu filter for output 1
+   * …
+
+= Flattened device tree representation =
+
+In FlattenedDeviceTree, the representation follows this logic.
+ * There is a timer device which is the root
+ * There is one filter per output line.
+
+{{{
+xicu@0xd2200000 {
+    device_type = "soclib:xicu:root";
+    input_lines = <2>;
+    ipis = <4>;
+    timers = <1>;
+    reg = <0xd2200000 0x1000>;
+
+    out@0 {
+        device_type = "soclib:xicu:filter";
+        parent = &{/xicu@0xd2200000};
+        output_line = <0>;
+        irq = <&{/cpus/Mips,32@0} 0>;
+    };
+
+    out@1 {
+        device_type = "soclib:xicu:filter";
+        parent = &{/xicu@0xd2200000};
+        output_line = <1>;
+        irq = <&{/cpus/Mips,32@1} 0>;
+    };
+
+    …
+};
+}}}
+
+== Timer designation ==
+
+Timer may be designated by a couple
+{{{<&{device_path} timer_id>}}}, maximum timer id is defined by
+the xicu root {{{"timers"}}} property.
+
+Timer may be used in {{{/chosen}}}, like:
+
+{{{
+chosen {
+    console = &{/tty@0xd0200000};
+    timer = <&{/xicu@0xd2200000} 0>;
+};
+}}}
+
+== Hardware IRQ input routing ==
+
+As usual, other components route their IRQs to targets; but as the
+''root'' is a timer device, IRQs must be routed to one of the output
+filters. Couple is:
+{{{<&{device_path} input_id>}}}, maximum hardware line id is defined by
+the xicu root {{{"input_lines"}}} property.
+
+{{{
+tty@0xd0200000 {
+    device_type = "soclib:tty";
+    tty_count = <1>;
+    reg = <0xd0200000 0x10>;
+    irq = <&{/xicu@0xd2200000/out@0} 0>;
+};
+}}}
+
+== IPI routing ==
+
+Likewise, in MutekH, IPIs are handled by the ICU device class.
+Processors must use xicu filters as IPI controllers. Couple is:
+{{{<&{device_path} ipi_id>}}}, maximum IPI id is defined by
+the xicu root {{{"ipis"}}} property.
+
+{{{
+Mips,32@0 {
+    name = "Mips,32";
+    device_type = "cpu";
+    reg = <0>;
+    icudev_type = "cpu:mips";
+    ipi = <&{/xicu@0/out@0} 0>;
+};
+}}}