From 1f36f73fe70560a2bd286a7abc8530fdc93af9ae Mon Sep 17 00:00:00 2001 From: Haavard Skinnemoen Date: Thu, 12 Aug 2010 13:52:54 +0700 Subject: avr32: Add simple paging support Use the MMU hardware to set up 1:1 mappings between physical and virtual addresses. This allows us to bypass the cache when accessing the flash without having to do any physical-to-virtual address mapping in the CFI driver. The virtual memory mappings are defined at compile time through a sorted array of virtual memory range objects. When a TLB miss exception happens, the exception handler does a binary search through the array until it finds a matching entry and loads it into the TLB. The u-boot image itself is covered by a fixed TLB entry which is never replaced. This makes the 'saveenv' command work again on ATNGW100 and other boards using the CFI driver, hopefully without breaking any rules. Signed-off-by: Haavard Skinnemoen --- arch/avr32/include/asm/arch-at32ap700x/addrspace.h | 5 +- arch/avr32/include/asm/arch-at32ap700x/mmu.h | 66 ++++++++++++++++++++++ 2 files changed, 67 insertions(+), 4 deletions(-) create mode 100644 arch/avr32/include/asm/arch-at32ap700x/mmu.h (limited to 'arch/avr32/include') diff --git a/arch/avr32/include/asm/arch-at32ap700x/addrspace.h b/arch/avr32/include/asm/arch-at32ap700x/addrspace.h index 409eee3536..4edc1bd701 100644 --- a/arch/avr32/include/asm/arch-at32ap700x/addrspace.h +++ b/arch/avr32/include/asm/arch-at32ap700x/addrspace.h @@ -75,10 +75,7 @@ static inline void * phys_to_virt(unsigned long address) static inline void * map_physmem(phys_addr_t paddr, unsigned long len, unsigned long flags) { - if (flags == MAP_WRBACK) - return (void *)P1SEGADDR(paddr); - else - return (void *)P2SEGADDR(paddr); + return (void *)paddr; } #endif /* __ASM_AVR32_ADDRSPACE_H */ diff --git a/arch/avr32/include/asm/arch-at32ap700x/mmu.h b/arch/avr32/include/asm/arch-at32ap700x/mmu.h new file mode 100644 index 0000000000..fcd9a05609 --- /dev/null +++ b/arch/avr32/include/asm/arch-at32ap700x/mmu.h @@ -0,0 +1,66 @@ +/* + * In order to deal with the hardcoded u-boot requirement that virtual + * addresses are always mapped 1:1 with physical addresses, we implement + * a small virtual memory manager so that we can use the MMU hardware in + * order to get the caching properties right. + * + * A few pages (or possibly just one) are locked in the TLB permanently + * in order to avoid recursive TLB misses, but most pages are faulted in + * on demand. + */ +#ifndef __ASM_ARCH_MMU_H +#define __ASM_ARCH_MMU_H + +#include + +#define PAGE_SHIFT 20 +#define PAGE_SIZE (1UL << PAGE_SHIFT) +#define PAGE_ADDR_MASK (~(PAGE_SIZE - 1)) + +#define MMU_VMR_CACHE_NONE \ + (SYSREG_BF(AP, 3) | SYSREG_BF(SZ, 3) | SYSREG_BIT(TLBELO_D)) +#define MMU_VMR_CACHE_WBUF \ + (MMU_VMR_CACHE_NONE | SYSREG_BIT(B)) +#define MMU_VMR_CACHE_WRTHRU \ + (MMU_VMR_CACHE_NONE | SYSREG_BIT(TLBELO_C) | SYSREG_BIT(W)) +#define MMU_VMR_CACHE_WRBACK \ + (MMU_VMR_CACHE_WBUF | SYSREG_BIT(TLBELO_C)) + +/* + * This structure is used in our "page table". Instead of the usual + * x86-inspired radix tree, we let each entry cover an arbitrary-sized + * virtual address range and store them in a binary search tree. This is + * somewhat slower, but should use significantly less RAM, and we + * shouldn't get many TLB misses when using 1 MB pages anyway. + * + * With 1 MB pages, we need 12 bits to store the page number. In + * addition, we stick an Invalid bit in the high bit of virt_pgno (if + * set, it cannot possibly match any faulting page), and all the bits + * that need to be written to TLBELO in phys_pgno. + */ +struct mmu_vm_range { + uint16_t virt_pgno; + uint16_t nr_pages; + uint32_t phys; +}; + +/* + * An array of mmu_vm_range objects describing all pageable addresses. + * The array is sorted by virt_pgno so that the TLB miss exception + * handler can do a binary search to find the correct entry. + */ +extern struct mmu_vm_range mmu_vmr_table[]; + +/* + * Initialize the MMU. This will set up a fixed TLB entry for the static + * u-boot image at dest_addr and enable paging. + */ +void mmu_init_r(unsigned long dest_addr); + +/* + * Handle a TLB miss exception. This function is called directly from + * the exception vector table written in assembly. + */ +int mmu_handle_tlb_miss(void); + +#endif /* __ASM_ARCH_MMU_H */ -- cgit v1.2.1