From: cyril@ti•com (Cyril Chemparathy)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v4 02/13] ARM: LPAE: use phys_addr_t in alloc_init_pud()
Date: Fri, 1 Feb 2013 12:56:54 -0500 [thread overview]
Message-ID: <510C01E6.2040108@ti.com> (raw)
In-Reply-To: <510BFC84.2030902@gmail.com>
On 02/01/2013 12:33 PM, Subash Patel wrote:
> Hi Nicolas,
>
> On Thursday 31 January 2013 07:35 PM, Nicolas Pitre wrote:
>> On Fri, 1 Feb 2013, Hui Wang wrote:
>>
>>> Cyril Chemparathy wrote:
>>>> From: Vitaly Andrianov <vitalya@ti•com>
>>>>
>>>> This patch fixes the alloc_init_pud() function to use phys_addr_t
>>>> instead of
>>>> unsigned long when passing in the phys argument.
>>>>
>>>> This is an extension to commit 97092e0c56830457af0639f6bd904537a150ea4a
>>>> (ARM:
>>>> pgtable: use phys_addr_t for physical addresses), which applied similar
>>>> changes
>>>> elsewhere in the ARM memory management code.
>>>>
>>>> Signed-off-by: Vitaly Andrianov <vitalya@ti•com>
>>>> Signed-off-by: Cyril Chemparathy <cyril@ti•com>
>>>> Acked-by: Nicolas Pitre <nico@linaro•org>
>>>> Acked-by: Catalin Marinas <catalin.marinas@arm•com>
>>>> ---
>>>> arch/arm/mm/mmu.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
>>>> index 9f06102..ef43689 100644
>>>> --- a/arch/arm/mm/mmu.c
>>>> +++ b/arch/arm/mm/mmu.c
>>>> @@ -612,7 +612,8 @@ static void __init alloc_init_section(pud_t *pud,
>>>> unsigned long addr,
>>>> }
>>>> static void __init alloc_init_pud(pgd_t *pgd, unsigned long addr,
>>>> - unsigned long end, unsigned long phys, const struct mem_type
>>>> *type)
>>>> + unsigned long end, phys_addr_t phys,
>>>> + const struct mem_type *type)
>>>>
>>> The change is correct but seems useless so far. This function only be
>>> called
>>> from map_lowmem and devicemaps_init, from i know neither lowmem nor
>>> device io
>>> registers of existing platforms exceed 32bit address.
>>
>> It is not because you are not aware of any existing platforms with RAM
>> or device IO above the 4GB mark that they don't exist.
>>
>> For example, some LPAE systems have all their RAM located above the 4G
>> physical address mark. A simple (potentially non DMA capable) alias
>> exists in the low 32-bit address space to allow the system to boot and
>> switch to the real physical RAM addresses once the MMU is turned on.
>> Some of that RAM is still qualified as "low mem" i.e. the portion of RAM
>> that the kernel keeps permanently mapped in the 32-bit virtual space
>> even if all of it is above the 4G mark in physical space.
>
> I think he is right. You cannot have low_mem and devices in 36-bit
> areas. Atleast this is what I saw in one of the platforms on which I
> tested these patches. I am not sure what you mean by hardware address
> aliasing(as I have real RAM), but we need 32-bit areas to boot the CPU
> and I have mapped them for the LOW_MEM. But, I have used 36-bit areas
> for the HIGH_MEM. Since you said about aliasing DDR area in 32-bits, and
> then switching to 36-bit RAM, does the dma of the devices still use
> 32-bit aliased addresses?
>
> I haven't tested a configuration where LOW_MEM can have both 32-bit and
> 36-bit DDR PA though. I think its not possible too.
>
On the KeyStone platform, memory is located at 08:0000:0000, i.e.,
outside the 32-bit addressable range. The hardware provides a limited
aliased map of the very same memory at 8000:0000, but this alias is
limited and intended only for boot time usage.
We boot the system while running out of this 32-bit physical address
range. We then switch over to the high physical address range fairly
early in the kernel boot, by rewriting boot-time page tables and the
TTBRs. Once this switch over has happened, lowmem is indeed outside the
32-bit physical address space.
Thanks
-- Cyril.
next prev parent reply other threads:[~2013-02-01 17:56 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-31 21:58 [PATCH v4 00/13] ARM LPAE Fixes - Part 1 Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 01/13] ARM: LPAE: use signed arithmetic for mask definitions Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 02/13] ARM: LPAE: use phys_addr_t in alloc_init_pud() Cyril Chemparathy
2013-02-01 3:11 ` Hui Wang
2013-02-01 3:35 ` Nicolas Pitre
2013-02-01 5:40 ` Hui Wang
2013-02-01 17:33 ` Subash Patel
2013-02-01 17:56 ` Cyril Chemparathy [this message]
2013-02-01 18:14 ` Nicolas Pitre
2013-02-01 20:32 ` Subash Patel
2013-01-31 21:58 ` [PATCH v4 03/13] ARM: LPAE: use phys_addr_t in free_memmap() Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 04/13] ARM: LPAE: use phys_addr_t for initrd location Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 05/13] ARM: LPAE: use phys_addr_t in switch_mm() Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 06/13] ARM: LPAE: use 64-bit accessors for TTBR registers Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 07/13] ARM: LPAE: define ARCH_LOW_ADDRESS_LIMIT for bootmem Cyril Chemparathy
2013-02-01 3:42 ` Nicolas Pitre
2013-01-31 21:58 ` [PATCH v4 08/13] ARM: LPAE: factor out T1SZ and TTBR1 computations Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 09/13] ARM: LPAE: accomodate >32-bit addresses for page table base Cyril Chemparathy
2013-02-01 3:48 ` Nicolas Pitre
2013-01-31 21:58 ` [PATCH v4 10/13] ARM: mm: use physical addresses in highmem sanity checks Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 11/13] ARM: mm: cleanup checks for membank overlap with vmalloc area Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 12/13] ARM: mm: clean up membank size limit checks Cyril Chemparathy
2013-01-31 21:58 ` [PATCH v4 13/13] ARM: fix type of PHYS_PFN_OFFSET to unsigned long Cyril Chemparathy
2013-02-01 3:51 ` Nicolas Pitre
2013-02-01 4:00 ` [PATCH v4 00/13] ARM LPAE Fixes - Part 1 Nicolas Pitre
2013-02-01 15:10 ` Cyril Chemparathy
2013-02-01 15:14 ` Russell King - ARM Linux
2013-02-01 16:13 ` Cyril Chemparathy
2013-02-01 17:56 ` Nicolas Pitre
2013-02-01 20:21 ` Subash Patel
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