From mboxrd@z Thu Jan 1 00:00:00 1970 From: subashrp@gmail.com (Subash Patel) Date: Fri, 01 Feb 2013 09:33:56 -0800 Subject: [PATCH v4 02/13] ARM: LPAE: use phys_addr_t in alloc_init_pud() In-Reply-To: References: <1359669512-31276-1-git-send-email-cyril@ti.com> <1359669512-31276-3-git-send-email-cyril@ti.com> <510B327E.3050502@gmail.com> Message-ID: <510BFC84.2030902@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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 >>> >>> 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 >>> Signed-off-by: Cyril Chemparathy >>> Acked-by: Nicolas Pitre >>> Acked-by: Catalin Marinas >>> --- >>> 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. Regards, Subash > > > Nicolas > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo at vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >