linux-kernel - Re: [PATCH 18/28] of: create default early_init_dt_add_memory

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Date:	Tue, 17 Sep 2013 08:01:36 -0500
From:	Rob Herring <robherring2@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"grant.likely@...aro.org" <grant.likely@...aro.org>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	Will Deacon <Will.Deacon@....com>,
	James Hogan <james.hogan@...tec.com>,
	Michal Simek <monstr@...str.eu>,
	Jonas Bonn <jonas@...thpole.se>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"microblaze-uclinux@...e.uq.edu.au" 
	<microblaze-uclinux@...e.uq.edu.au>,
	"linux@...nrisc.net" <linux@...nrisc.net>
Subject: Re: [PATCH 18/28] of: create default early_init_dt_add_memory_arch

On Tue, Sep 17, 2013 at 3:46 AM, Catalin Marinas
<catalin.marinas@....com> wrote:
> On 17 Sep 2013, at 00:09, Rob Herring <robherring2@...il.com> wrote:
>> --- a/arch/arm64/kernel/setup.c
>> +++ b/arch/arm64/kernel/setup.c
>> @@ -147,24 +147,6 @@ static void __init setup_machine_fdt(phys_addr_t dt_phys)
>>       pr_info("Machine: %s\n", machine_name);
>> }
>>
>> -void __init early_init_dt_add_memory_arch(u64 base, u64 size)
>> -{
>> -     base &= PAGE_MASK;
>> -     size &= PAGE_MASK;
>> -     if (base + size < PHYS_OFFSET) {
>> -             pr_warning("Ignoring memory block 0x%llx - 0x%llx\n",
>> -                        base, base + size);
>> -             return;
>> -     }
>> -     if (base < PHYS_OFFSET) {
>> -             pr_warning("Ignoring memory range 0x%llx - 0x%llx\n",
>> -                        base, PHYS_OFFSET);
>> -             size -= PHYS_OFFSET - base;
>> -             base = PHYS_OFFSET;
>> -     }
>> -     memblock_add(base, size);
>> -}
>> -
>> /*
>>  * Limit the memory size that was specified via FDT.
>>  */
>
> ...
>
>> --- a/drivers/of/fdt.c
>> +++ b/drivers/of/fdt.c
>> @@ -688,6 +688,17 @@ u64 __init dt_mem_next_cell(int s, __be32 **cellp)
>>       return of_read_number(p, s);
>> }
>>
>> +void __init __weak early_init_dt_add_memory_arch(u64 base, u64 size)
>> +{
>> +#ifdef CONFIG_HAVE_MEMBLOCK
>> +     base &= PAGE_MASK;
>> +     size &= PAGE_MASK;
>> +     memblock_add(base, size);
>> +#else
>> +     pr_err("%s: ignoring memory (%llx, %llx)\n", __func__, base, size);
>> +#endif
>> +}
>
> Are the arm64 changes equivalent here?  There are some safety checks to
> cope with the kernel being loaded at a higher offset than the
> recommended one (PHYS_OFFSET calculated automatically).

I tried to keep that, but PHYS_OFFSET is not universally defined. My
reasoning is this range checking is hardly specific to an
architecture. Perhaps if memory always starts at 0 you don't need it.
If arm64 really needs these checks, then all architectures do.

Perhaps "__virt_to_phys(PAGE_OFFSET)" instead of PHYS_OFFSET would work for all?

Rob
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