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

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Date:	Mon, 06 Jun 2011 16:32:17 +0530
From:	Suzuki Poulose <suzuki@...ibm.com>
To:	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
CC:	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Simon Horman <horms@...ge.net.au>,
	Josh Boyer <jwboyer@...ux.vnet.ibm.com>,
	linux ppc dev <linuxppc-dev@...ts.ozlabs.org>,
	Vivek Goyal <vgoyal@...hat.com>
Subject: Re: [RFC][PATCH] powerpc: Use the #address-cells information to parse
 memory/reg

On 06/06/11 14:21, Sebastian Andrzej Siewior wrote:
> 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.

Yes, you are right. Porting this patch over to ppc64 is in my TODO list.

> 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.
OK

>>> 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.
>
OK. I was using (unsigned long) to get the word size on the machine. Given
this code is duplicated in ppc64, thought of having a generic code which works
fine for all ppcXX. As you mentioned, if we go about moving to a single copy of
fdt code, using long would help us.

>>> + 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.

Thanks
Suzuki
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