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

From: Sebastian Andrzej Siewior <[email-masked]>
Date: Mon, 06 Jun 2011 10:51:26 +0200

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