mirror of
https://github.com/brain-hackers/u-boot-brain
synced 2024-07-21 10:38:00 +09:00
1f36f73fe7
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 <haavard.skinnemoen@atmel.com>
79 lines
2.0 KiB
C
79 lines
2.0 KiB
C
#include <common.h>
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#include <asm/arch/mmu.h>
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#include <asm/sysreg.h>
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void mmu_init_r(unsigned long dest_addr)
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{
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uintptr_t vmr_table_addr;
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/* Round monitor address down to the nearest page boundary */
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dest_addr &= PAGE_ADDR_MASK;
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/* Initialize TLB entry 0 to cover the monitor, and lock it */
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sysreg_write(TLBEHI, dest_addr | SYSREG_BIT(TLBEHI_V));
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sysreg_write(TLBELO, dest_addr | MMU_VMR_CACHE_WRBACK);
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sysreg_write(MMUCR, SYSREG_BF(DRP, 0) | SYSREG_BF(DLA, 1)
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| SYSREG_BIT(MMUCR_S) | SYSREG_BIT(M));
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__builtin_tlbw();
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/*
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* Calculate the address of the VM range table in a PC-relative
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* manner to make sure we hit the SDRAM and not the flash.
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*/
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vmr_table_addr = (uintptr_t)&mmu_vmr_table;
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sysreg_write(PTBR, vmr_table_addr);
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printf("VMR table @ 0x%08x\n", vmr_table_addr);
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/* Enable paging */
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sysreg_write(MMUCR, SYSREG_BF(DRP, 1) | SYSREG_BF(DLA, 1)
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| SYSREG_BIT(MMUCR_S) | SYSREG_BIT(M) | SYSREG_BIT(E));
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}
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int mmu_handle_tlb_miss(void)
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{
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const struct mmu_vm_range *vmr_table;
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const struct mmu_vm_range *vmr;
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unsigned int fault_pgno;
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int first, last;
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fault_pgno = sysreg_read(TLBEAR) >> PAGE_SHIFT;
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vmr_table = (const struct mmu_vm_range *)sysreg_read(PTBR);
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/* Do a binary search through the VM ranges */
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first = 0;
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last = CONFIG_SYS_NR_VM_REGIONS;
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while (first < last) {
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unsigned int start;
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int middle;
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/* Pick the entry in the middle of the remaining range */
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middle = (first + last) >> 1;
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vmr = &vmr_table[middle];
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start = vmr->virt_pgno;
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/* Do the bisection thing */
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if (fault_pgno < start) {
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last = middle;
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} else if (fault_pgno >= (start + vmr->nr_pages)) {
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first = middle + 1;
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} else {
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/* Got it; let's slam it into the TLB */
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uint32_t tlbelo;
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tlbelo = vmr->phys & ~PAGE_ADDR_MASK;
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tlbelo |= fault_pgno << PAGE_SHIFT;
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sysreg_write(TLBELO, tlbelo);
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__builtin_tlbw();
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/* Zero means success */
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return 0;
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}
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}
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/*
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* Didn't find any matching entries. Return a nonzero value to
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* indicate that this should be treated as a fatal exception.
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*/
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return -1;
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}
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