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authorSuzuki Poulose <suzuki@in.ibm.com>2011-12-14 22:58:37 +0000
committerJosh Boyer <jwboyer@gmail.com>2011-12-20 10:21:34 -0500
commit368ff8f14d6ed8e9fd3b7c2156f2607719bf5a7a (patch)
treea52996c9083368fc3c5297bc45d5f67189de9ad7 /arch/powerpc/mm
parent9c5f7d39a86316cd13baf973c90ed27f9f1cc979 (diff)
powerpc: Define virtual-physical translations for RELOCATABLE
We find the runtime address of _stext and relocate ourselves based on the following calculation. virtual_base = ALIGN(KERNELBASE,KERNEL_TLB_PIN_SIZE) + MODULO(_stext.run,KERNEL_TLB_PIN_SIZE) relocate() is called with the Effective Virtual Base Address (as shown below) | Phys. Addr| Virt. Addr | Page |------------------------| Boundary | | | | | | | | | Kernel Load |___________|_ __ _ _ _ _|<- Effective Addr(_stext)| | ^ |Virt. Base Addr | | | | | | | | | |reloc_offset| | | | | | | | | | |______v_____|<-(KERNELBASE)%TLB_SIZE | | | | | | | | | Page |-----------|------------| Boundary | | | On BookE, we need __va() & __pa() early in the boot process to access the device tree. Currently this has been defined as : #define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) - PHYSICAL_START + KERNELBASE) where: PHYSICAL_START is kernstart_addr - a variable updated at runtime. KERNELBASE is the compile time Virtual base address of kernel. This won't work for us, as kernstart_addr is dynamic and will yield different results for __va()/__pa() for same mapping. e.g., Let the kernel be loaded at 64MB and KERNELBASE be 0xc0000000 (same as PAGE_OFFSET). In this case, we would be mapping 0 to 0xc0000000, and kernstart_addr = 64M Now __va(1MB) = (0x100000) - (0x4000000) + 0xc0000000 = 0xbc100000 , which is wrong. it should be : 0xc0000000 + 0x100000 = 0xc0100000 On platforms which support AMP, like PPC_47x (based on 44x), the kernel could be loaded at highmem. Hence we cannot always depend on the compile time constants for mapping. Here are the possible solutions: 1) Update kernstart_addr(PHSYICAL_START) to match the Physical address of compile time KERNELBASE value, instead of the actual Physical_Address(_stext). The disadvantage is that we may break other users of PHYSICAL_START. They could be replaced with __pa(_stext). 2) Redefine __va() & __pa() with relocation offset #ifdef CONFIG_RELOCATABLE_PPC32 #define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) - PHYSICAL_START + (KERNELBASE + RELOC_OFFSET))) #define __pa(x) ((unsigned long)(x) + PHYSICAL_START - (KERNELBASE + RELOC_OFFSET)) #endif where, RELOC_OFFSET could be a) A variable, say relocation_offset (like kernstart_addr), updated at boot time. This impacts performance, as we have to load an additional variable from memory. OR b) #define RELOC_OFFSET ((PHYSICAL_START & PPC_PIN_SIZE_OFFSET_MASK) - \ (KERNELBASE & PPC_PIN_SIZE_OFFSET_MASK)) This introduces more calculations for doing the translation. 3) Redefine __va() & __pa() with a new variable i.e, #define __va(x) ((void *)(unsigned long)((phys_addr_t)(x) + VIRT_PHYS_OFFSET)) where VIRT_PHYS_OFFSET : #ifdef CONFIG_RELOCATABLE_PPC32 #define VIRT_PHYS_OFFSET virt_phys_offset #else #define VIRT_PHYS_OFFSET (KERNELBASE - PHYSICAL_START) #endif /* CONFIG_RELOCATABLE_PPC32 */ where virt_phy_offset is updated at runtime to : Effective KERNELBASE - kernstart_addr. Taking our example, above: virt_phys_offset = effective_kernelstart_vaddr - kernstart_addr = 0xc0400000 - 0x400000 = 0xc0000000 and __va(0x100000) = 0xc0000000 + 0x100000 = 0xc0100000 which is what we want. I have implemented (3) in the following patch which has same cost of operation as the existing one. I have tested the patches on 440x platforms only. However this should work fine for PPC_47x also, as we only depend on the runtime address and the current TLB XLAT entry for the startup code, which is available in r25. I don't have access to a 47x board yet. So, it would be great if somebody could test this on 47x. Signed-off-by: Suzuki K. Poulose <suzuki@in.ibm.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Kumar Gala <galak@kernel.crashing.org> Cc: linuxppc-dev <linuxppc-dev@lists.ozlabs.org> Signed-off-by: Josh Boyer <jwboyer@gmail.com>
Diffstat (limited to 'arch/powerpc/mm')
-rw-r--r--arch/powerpc/mm/init_32.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/arch/powerpc/mm/init_32.c b/arch/powerpc/mm/init_32.c
index 161cefde5c1..60a4e4e84e8 100644
--- a/arch/powerpc/mm/init_32.c
+++ b/arch/powerpc/mm/init_32.c
@@ -65,6 +65,13 @@ phys_addr_t memstart_addr = (phys_addr_t)~0ull;
EXPORT_SYMBOL(memstart_addr);
phys_addr_t kernstart_addr;
EXPORT_SYMBOL(kernstart_addr);
+
+#ifdef CONFIG_RELOCATABLE_PPC32
+/* Used in __va()/__pa() */
+long long virt_phys_offset;
+EXPORT_SYMBOL(virt_phys_offset);
+#endif
+
phys_addr_t lowmem_end_addr;
int boot_mapsize;