Re: [RFC][PATCH] powerpc: Use the #address-cells information to parse memory/reg

[Sebastian Andrzej Siewior]

Suzuki Poulose wrote:

Could you please let me know your thoughts/comments about this patch ?

I'm mostly fine with it.

Maaxim copied fs2dt.c from ppc64 to ppc. So I guess ppc64 has the same
problem. ARM and MIPS is soon having DT support and kexec is probably also
on their list so I would hate to see them to either copy the DT parsing
file or having their own implementation.

Maybe we should try to use libfdt for dt parsing. It has /proc import
support so it should be fine for our needs. It is already in tree and used
by ppc32 if a basic dtb is specified. I'm not sure if the /proc interface
is part of dtc or libfdt.

I'm not saying this has to be done now but maybe later before ARM and/or
MIPS comes along needs something similar for their needs. If the libfdt is
too complex for sucking in the dtb from /proc then maybe something else
that generic and can be shared between booth ppc architectures and the
other ones.

Thanks
Suzuki

Index: kexec-tools-2.0.4/kexec/arch/ppc/kexec-ppc.c
===================================================================
--- kexec-tools-2.0.4.orig/kexec/arch/ppc/kexec-ppc.c
+++ kexec-tools-2.0.4/kexec/arch/ppc/kexec-ppc.c
@@ -34,6 +35,92 @@ unsigned int rtas_base, rtas_size;
int max_memory_ranges;
const char *ramdisk;

+/*
+ * Reads the #address-cells and #size-cells on this platform.
+ * This is used to parse the memory/reg info from the device-tree
+ */
+int init_memory_region_info()
+{
+ size_t res = 0;
+ FILE *fp;
+ char *file;
+
+ file = "/proc/device-tree/#address-cells";
+ fp = fopen(file, "r");
+ if (!fp) {
+ fprintf(stderr,"Unable to open %s\n", file);
+ return -1;
+ }
+
+ res = fread(&dt_address_cells,sizeof(unsigned long),1,fp);
+ if (res != 1) {
+ fprintf(stderr,"Error reading %s\n", file);
+ return -1;
+ }
+ fclose(fp);
+ dt_address_cells *= sizeof(unsigned long);

This should be sizeof(unsigned int). I know we on 32bit.

+ file = "/proc/device-tree/#size-cells";
+ fp = fopen(file, "r");
+ if (!fp) {
+ fprintf(stderr,"Unable to open %s\n", file);
+ return -1;
+ }
+
+ res = fread(&dt_size_cells,sizeof(unsigned long),1,fp);
+ if (res != 1) {
+ fprintf(stderr,"Error reading %s\n", file);
+ return -1;
+ }
+ fclose(fp);
+ dt_size_cells *= sizeof(unsigned long);

same here.

+
+ return 0;
+}
+

Sebastian

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