[U-Boot] [PATCH 03/26] ARM: cp15: setup mmu and enable dcache

[Heiko Schocher <hs@denx.de>]

Hello V, Aneesh,

V, Aneesh wrote:
> Hello Heiko Schocher,
> 
>> bounces at lists.denx.de] On Behalf Of Heiko Schocher
>> +static inline void mmu_setup(void)
>> +{
>> +	static u32 __attribute__((aligned(16384))) page_table[4096];
>> +	bd_t *bd = gd->bd;
>> +	int i, j;
>> +	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 (j = 0; j < CONFIG_NR_DRAM_BANKS; j++) {
>> +		for (i = bd->bi_dram[j].start >> 20;
>> +			i < (bd->bi_dram[j].start + bd->bi_dram[j].size)
>>>> 20;
>> +			i++) {
>> +			page_table[i] = i << 20 | (3 << 10) | CACHE_SETUP;
>> +		}
>> +	}
>> +
>> +	/* 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);
> 
> I think you need to invalidate caches, TLB, branch-prediction array etc before enabling MMU. I don't think the caches are guaranteed to be invalidated at power on reset.
> 
> Please find below some experimental(but working) code I had written  for enabling MMU and caches for an internal project. It's written for the ARM RVCT tool chain. So, it will not compile straight away on GCC.
> 
> It has code for invalidating caches, TLB, Branch prediction array etc. Also, it uses macros for the bit fields in the SCTLR register. However, the L1 D$ cleaning is not generic. It assumes the size and organization of the L1 cache. 
> arch/arm/cpu/armv7/omap3/cache.S has a more generic implementation of invalidating the entire L1 D$.
> 
> In case you find it useful, you are welcome to reuse any part of this code. If you want me to create a patch myself I am open to do that too.

Thanks!

I try to try out your suggestions, if you can make a patch
(and try it on a plattform it would be great ;-)

bye,
Heiko
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