Kexec on arch powerpc, device trees

[Simon Kagstrom]

Hi!

I'm looking a bit at adding kexec support for our mpc8347-based board
running a 2.6.21 kernel. Since the board isn't a "PPC_MULTIPLATFORM"
one, I did a quick patch to the Kconfig file to allow enabling Kexec
for our own board. The patch below then adds the kexec machine
callbacks for our board, and this is enough to build.

I ran into two problems though: First, /proc/iomem did not contain any
"System RAM", so the kexec userspace tool ended up without any usable
memory regions and fails because of that. I thought this would be
handled by the device tree support, where we have a node for the memory:

	memory {
		device_type = "memory";
		reg = <00000000 20000000>;
	};

but apparently it isn't. Anyway, the add_ram_region_iomem() function
adds a "System RAM" region for all "memory" nodes in the device tree.


However, even after this kexec still fails:

   bash-3.1# /kexec -l /vmlinux
   Invalid memory segment 0xc0000000 - 0xc0304fff

this time because the "System RAM" is really 0x00000000-0x20000000. If
I use the --gamecube=1 option, kexec will load the kernel, but when
trying to start it the board will just crash:

   bash-3.1# /kexec -e -d
   [ 1579.005719] Starting new kernel
   <end up in U-boot here>

So some questions: Is the --gamecube=1 option really meant to be used
without a gamecube and should the first version really fail? Is the
"System RAM" usage correct? Are there any similar freescale-based
boards which have kexec support?

// Simon

Index: linux-2.6.21-standard/arch/powerpc/platforms/83xx/cmxb.c
===================================================================
--- linux-2.6.21-standard.orig/arch/powerpc/platforms/83xx/cmxb.c
+++ linux-2.6.21-standard/arch/powerpc/platforms/83xx/cmxb.c
@@ -23,6 +23,7 @@
 #include <linux/delay.h>
 #include <linux/seq_file.h>
 #include <linux/root_dev.h>
+#include <linux/bootmem.h>
 
 #include <asm/system.h>
 #include <asm/atomic.h>
@@ -35,6 +36,7 @@
 #include <asm/prom.h>
 #include <asm/udbg.h>
 #include <sysdev/fsl_soc.h>
+#include <linux/kexec.h>
 
 #include "mpc83xx.h"
 #include "cmxb.h"
@@ -44,6 +46,31 @@ unsigned long isa_io_base = 0;
 unsigned long isa_mem_base = 0;
 #endif
 
+
+static void add_ram_region_iomem(void)
+{
+	struct device_node *np;
+	struct resource *res;
+	struct resource of_resource;
+
+	for (np = NULL; (np = of_find_node_by_type(np, "memory")) != NULL;) {
+                if (of_address_to_resource(np, 0, &of_resource)) {
+                        printk(KERN_ERR "Could not convert memory node to resource\n");
+                        of_node_put(np);
+                        return;
+                }
+		res = alloc_bootmem(sizeof(struct resource));
+
+		res->name = "System RAM";
+		res->start = of_resource.start;
+		res->end = of_resource.end;
+		res->flags = of_resource.flags;
+		request_resource(&iomem_resource, res);
+                of_node_put(np);
+	}
+}
+
+
 /* ************************************************************************
  *
  * Setup the architecture
@@ -62,6 +89,7 @@ static void __init cmxb_setup_arch(void)
 
 	ppc_md.pci_exclude_device = mpc83xx_exclude_device;
 #endif
+        add_ram_region_iomem();
 }
 
 static void __init cmxb_init_IRQ(void)
@@ -100,4 +128,9 @@ define_machine(cmxb) {
 	.time_init		= mpc83xx_time_init,
 	.calibrate_decr		= generic_calibrate_decr,
 	.progress		= udbg_progress,
+#ifdef CONFIG_KEXEC
+	.machine_kexec		= default_machine_kexec,
+	.machine_kexec_prepare	= default_machine_kexec_prepare,
+	.machine_crash_shutdown	= default_machine_crash_shutdown,
+#endif
 };