This has been tested on at91sam9263 and STN8815. Again, I didn't check if it has bad effects on non-arm926 cores.
Initially I had a "done" bit to only set up page tables at the beginning. However, since the aligmnent requirement was for the whole object file, this extra integer tool 16kB in BSS, so I chose to remove it.
Also, note not all boards use PHYS_SDRAM, but it looks like it's the most used name (more than CONFIG_SYS_DRAM_BASE for example).
rebased for full arm relocation from Heiko Schocher hs@denx.de
Signed-off-by: Alessandro Rubini rubini@gnudd.com --- arch/arm/lib/cache-cp15.c | 38 ++++++++++++++++++++++++++++++++++++++ 1 files changed, 38 insertions(+), 0 deletions(-)
diff --git a/arch/arm/lib/cache-cp15.c b/arch/arm/lib/cache-cp15.c index 62ed54f..11e64d8 100644 --- a/arch/arm/lib/cache-cp15.c +++ b/arch/arm/lib/cache-cp15.c @@ -32,6 +32,36 @@ static void cp_delay (void) /* copro seems to need some delay between reading and writing */ for (i = 0; i < 100; i++) nop(); + asm volatile("" : : : "memory"); +} + +/* to activate the MMU we need to set up virtual memory: use 1M areas in bss */ +static inline void mmu_setup(void) +{ + static u32 __attribute__((aligned(16384))) page_table[4096]; + int i; + u32 reg; + + /* Set up an identity-mapping for all 4GB, rw for everyone */ + for (i = 0; i < 4096; i++) + page_table[i] = i << 20 | (3 << 10) | 0x12; + /* Then, enable cacheable and bufferable for RAM only */ + for (i = PHYS_SDRAM >> 20; + i < ( PHYS_SDRAM + PHYS_SDRAM_SIZE) >> 20; + i++) { + page_table[i] = i << 20 | (3 << 10) | 0x1e; + } + /* Copy the page table address to cp15 */ + asm volatile("mcr p15, 0, %0, c2, c0, 0" + : : "r" (page_table) : "memory"); + /* Set the access control to all-supervisor */ + asm volatile("mcr p15, 0, %0, c3, c0, 0" + : : "r" (~0)); + /* and enable the mmu */ + reg = get_cr(); /* get control reg. */ + cp_delay(); + set_cr(reg | CR_M); + }
/* cache_bit must be either CR_I or CR_C */ @@ -39,6 +69,9 @@ static void cache_enable(uint32_t cache_bit) { uint32_t reg;
+ /* The data cache is not active unless the mmu is enabled too */ + if (cache_bit == CR_C) + mmu_setup(); reg = get_cr(); /* get control reg. */ cp_delay(); set_cr(reg | cache_bit); @@ -49,6 +82,11 @@ static void cache_disable(uint32_t cache_bit) { uint32_t reg;
+ if (cache_bit == CR_C) { + /* if disabling data cache, disable mmu too */ + cache_bit |= CR_M; + flush_cache(0, ~0); + } reg = get_cr(); cp_delay(); set_cr(reg & ~cache_bit);