[U-Boot] [PATCH v3 03/10] armv7: cache maintenance operations for armv7

Aneesh V
2011-05-17T09:17:46Z

On Monday 16 May 2011 12:21 AM, Wolfgang Denk wrote:
> Dear Aneesh V,
>
> In message<1305202276-27784-4-git-send-email-aneesh@ti.com> you wrote:
>> - Add a framework for layered cache maintenance
>> - separate out SOC specific outer cache maintenance from
>> maintenance of caches known to CPU
>>
>> - Add generic ARMv7 cache maintenance operations that affect all
>> caches known to ARMv7 CPUs. For instance in Cortex-A8 these
>> opertions will affect both L1 and L2 caches. In Cortex-A9
>> these will affect only L1 cache
>>
>> - D-cache operations supported:
>> - Invalidate entire D-cache
Needed before enabling the caches.
>> - Invalidate D-cache range
Needed if you are doing DMA.
>> - Flush(clean& invalidate) entire D-cache
Needed before Linux before disabling the caches.
>> - Flush D-cache range
Needed in case of DMA out.

>
> How much of this is actually needed in the context of U-Boot?

Please see above. As far as I know OMAP doesn't do DMA in U-Boot.

>
> ...
>> + for (way = num_ways - 1; way>= 0 ; way--)
>> + for (set = num_sets - 1; set>= 0; set--) {
>> + setway = (level<< 1) | (set<< log2_line_len) |
>> + (way<< way_shift);
>> + /* Invalidate data/unified cache line by set/way */
>> + asm volatile (" mcr p15, 0, %0, c7, c6, 2"
>> + : : "r" (setway));
>> + }
>
> Braces needed for multiline for(). Please fix globally.

Ok.

>
> ...

>> + if (operation == ARMV7_DCACHE_INVAL_ALL)
>> + v7_inval_dcache_level_setway(level, num_sets, num_ways,
>> + way_shift, log2_line_len);
>> + else if (operation == ARMV7_DCACHE_CLEAN_INVAL_ALL)
>> + v7_clean_inval_dcache_level_setway(level, num_sets, num_ways,
>> + way_shift, log2_line_len);
>
> Braces needed for multiline statements. Please fix globally.
>
>> + for (mva = start; mva< stop; mva = mva + line_len)
>> + /* DCCIMVAC - Clean& Invalidate data cache by MVA to PoC */
>> + asm volatile ("mcr p15, 0, %0, c7, c14, 1" : : "r" (mva));
>
> And again etc. etc.
>
> ...
>> +void invalidate_dcache_all(void)
>> +{
>> +}
>> +
>> +void flush_dcache_all(void)
>> +{
>> +}
>> +
>> +void invalidate_dcache_range(unsigned long start, unsigned long stop)
>> +{
>> +}
>> +
>> +void flush_dcache_range(unsigned long start, unsigned long stop)
>> +{
>> +}
>> +
>> +void arm_init_before_mmu(void)
>> +{
>> +}
>> +
>> +void flush_cache(unsigned long start, unsigned long size)
>> +{
>> +}
>
> Please do not add dead code. I consider it misleading to have
> functions which promise to perform something, and actually do nothing.

These are empty only in the else part of an #ifdef. When cache support
is compiled out these need to be empty.

best regards,
Aneesh