Hi Albert,
On 08/08/2011 04:01 PM, Albert ARIBAUD wrote:
Hi Hong Xu,
Le 08/08/2011 05:20, Hong Xu a écrit :
After DMA operation, we need to maintain D-Cache coherency. So that the DCache must be invalidated (hence CPU will fetch
[...]
unaligned buffer and only round up/down the buffer address
- mva = start;
- if ((mva& (cache_line_len - 1)) != 0) {
- printf("WARNING: %s - unaligned buffer detected, starting "
I'd rather have a message about "cache", not "buffer", e.g.
printf("WARNING: %s - start address %x is not aligned\n" __FUNCTION__, start);
OK
- mva&= ~(cache_line_len - 1);
- }
- if ((stop& (cache_line_len - 1)) != 0) {
- printf("WARNING: %s - unaligned buffer detected, ending "
- "address: 0x%08x\n", __FUNCTION__, stop);
Ditto.
OK
- stop = (stop | (cache_line_len - 1)) + 1;
- }
- while (mva< stop) {
- asm("mcr p15, 0, %0, c7, c6, 1" : : "r"(mva));
- mva += cache_line_len;
- }
Thinking more about the degenerate case -- why not round *up* the start address, and round *down* the stop address, that is, *reduce* the area to the aligned portion rather than *expand* it into the unknown? That would make data in "partially owned" cache lines safe from unwanted invalidation. OTOH, it would not completely invalidate the caller's data, but at least the malfunction would appear in the faulty calling code, not elsewhere.
Opinions?
Agree :)
BR, Eric