[Linux-Xtensa] Cache flushing when transitioning from U-Boot to Kernel

czankel chris at zankel.net
Thu Jul 11 11:16:08 PDT 2013


In the current situation, the U-Boot version I've been working on 
doesn't flush the caches, and the kernel invalidates (not write-back!) 
all caches, so data still in the data cache can be lost (in fact, it 
is).  The options are:

1. Any boot loader, reset vector, etc. flushes the caches (write-back)
2. The kernel uses write-back instead of invalidate

I haven't seen any other architecture flushing the caches in U-Boot, and 
it feels to me that when you jump to the kernel, any loader (or reset 
vector) would already have initialized the caches, so there's really no 
need to do anything in the kernel? In cases where we (re-) initialize 
the MMU, we probably need to flush the caches before messing with the MMU?

Am I missing something? Opinions?


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