Subject: Re: [PATCH 3/3] First cut at PReP support for arch/powerpc

From: Segher Boessenkool <[email-masked]>
Date: Thu, 28 Jun 2007 10:59:35 +0200

> Here is an implementation to allow PReP systems to boot under the
> arch/powerpc codebase, one of the few remaining platforms supported in
> arch/ppc but not so far in arch/powerpc.

> Too big for the list, the patch is at:
> 	http://ozlabs.org/~dgibson/home/prep-support

Too lazy to split the patch into bite-size chunks, you mean ;-)

Anyway, here goes the DTS bits:

+/*
+ * PReP skeleton device tree
+ *
+ * Paul Mackerras <[email-masked]>
+ */
+
+/ {
+	device_type = "prep";
+	model = "IBM,PReP";

Not specific enough, leave it out or fill it in in the bootwrapper.

+	compatible = "prep";

Maybe fill this in, too.

+	#address-cells = <1>;
+	#size-cells = <1>;
+
+	cpus {
+		#address-cells = <1>;
+		#size-cells = <0>;
+
+		cpu@0 {

Do all (supported) PReP boards have one CPU only?

+			device_type = "cpu";
+			reg = <0>;
+			clock-frequency = <0>; // filled in by bootwrapper
+			bus-frequency = <0>; // filled in by bootwrapper
+			timebase-frequency = <0>; // filled in by bootwrapper
+			i-cache-line-size = <0>; // filled in by bootwrapper
+			d-cache-line-size = <0>; // filled in by bootwrapper
+			d-cache-size = <0>; // filled in by bootwrapper
+			i-cache-size = <0>; // filled in by bootwrapper
+			external-control;

Really?

+			graphics;
+			performance-monitor;
+
+			l2-cache {
+				device_type = "cache";
+				i-cache-size = <00100000>;
+				d-cache-size = <00100000>;
+				i-cache-sets = <00008000>;
+				d-cache-sets = <00008000>;
+				i-cache-line-size = <00000020>;
+				d-cache-line-size = <00000020>;

Drop the leading zeroes, they make my head spin :-)

+				cache-unified;
+			};
+		};
+	};
+
+	memory {
+		device_type = "memory";
+		// dummy range here, zImage wrapper will fill in the actual
+		// amount of memory from the residual data
+		reg = <00000000 00000000>;
+	};
+
+	pci@80000000 {
+		device_type = "pci";
+		compatible = "prep";

Is that specific enough?

+		clock-frequency = <01fca055>;
+		reg = <80000000 7effffff>;
+		8259-interrupt-acknowledge = <bffffff0>;
+		#address-cells = <3>;
+		#size-cells = <2>;
+		ranges=<01000000 00000000 00000000 80000000 00000000 00800000
+			01000000 00000000 00800000 81000000 00000000 3e800000
+			02000000 00000000 00000000 c0000000 00000000 01000000
+			02000000 00000000 01000000 c1000000 00000000 3e000000>;
+		interrupt-map-mask = <f800 0 0 7>;
+		interrupt-map = <6000 0 0 1	&MPIC 6 0
+				 8000 0 0 1	&MPIC 7 0
+				 9000 0 0 1	&MPIC 2 0
+				 b000 0 0 1	&MPIC 1 0>;

I can't believe this "ranges" and interrupt mapping will
work on all PReP systems...

+		isa {
+			device_type = "isa";
+			#address-cells = <2>;
+			#size-cells = <1>;
+			#interrupt-cells = <2>;
+			ranges = <00000001 00000000
+				  01005800 00000000 00000000  00010000
+				  00000000 00000000
+				  02005800 00000000 00000000  01000000>;
+
+			parallel {
+				device_type = "parallel";
+				compatible = "ecp", "pnpPNP,400";

"pnpPNP,401", "pnpPNP,400"

+				reg =  <00000001 000003bc  00000008
+					00000001 000007bc  00000006>;
+				interrupts = <00000007 00000003>;
+				interrupt-parent = <&PIC8259>;
+			};
+
+			serial@3f8 {
+				device_type = "serial";
+				compatible = "pnpPNP,501";

"pnpPNP,501", "pnpPNP,500" I'd say.  Many/some device
tree users will only care it is _some_ 8250 family thing.

+				clock-frequency = <001c2000>;
+				reg =  <00000001 000003f8  00000008>;
+				interrupts = <00000004 00000003>;
+				interrupt-parent = <&PIC8259>;
+			};
+			serial@2f8 {
+				device_type = "serial";
+				compatible = "pnpPNP,501";
+				clock-frequency = <001c2000>;
+				reg =  <00000001 000002f8  00000008>;
+				interrupts = <00000003 00000003>;
+				interrupt-parent = <&PIC8259>;
+			};
+			PIC8259: interrupt-controller {
+				device_type = "i8259";

device_type = "interrupt-controller".

+				compatible = "prep,iic";
+				reg = <	00000001 00000020  00000002
+					00000001 000000a0  00000002
+					00000001 000004d0  00000002>;
+				interrupts = <00000000 00000003
+					      00000002 00000003>;
+				interrupt-parent = <&MPIC>;
+			};
+		};
+
+		MPIC: interrupt-controller@d {
+			device_type = "open-pic";

device_type = "interrupt-controller".

+			compatible = "mpic";
+			reg = <	00006800 00000000 00000000  00000000 00000000
+				02006810 00000000 00000000  00000000 00040000>;
+			assigned-addresses = <
+				82006810 00000000 3afc0000  00000000 00040000>;
+		};
+	};
+
+	chosen {
+		linux,stdout-path = "/pci/isa/serial@3f8";
+	};
+};

What is the plan here -- have the bootwrapper build the
device tree / fill in the details from the residual data?

Segher