On 11/07/11 20:43, Josh Poimboeuf wrote:
On Fri, 2011-11-04 at 14:06 +0530, Suzuki Poulose wrote:
On 11/03/11 05:06, Josh Poimboeuf wrote:
On Tue, 2011-10-25 at 17:23 +0530, Suzuki K. Poulose wrote:
@@ -137,6 +137,9 @@ get_type:
lwz r0, 8(r9) /* r_addend */
add r0, r0, r3 /* final addend */
stwx r0, r4, r7 /* memory[r4+r7]) = (u32)r0 */
+ dcbst r4,r7 /* flush dcache line to memory */
+ sync /* wait for flush to complete */
+ icbi r4,r7 /* invalidate icache line */
Doing it this way has two drawbacks :
1) Placing it here in relocate would do the flushing for each and every update.
I agree. My kernel had around 80,000 relocations, which means 80,000
d-cache line flushes (for a 32k d-cache) and 80,000 i-cache line
invalidates (for a 32k i-cache). Which is obviously a little overkill.
Although I didn't notice a performance hit during boot.
2) I would like to keep this code as generic as possible for the PPC32 code.
Could we move this to the place from relocate is called and flush the d-cache
and
i-cache entirely ?
Why not put the cache flushing code at the end of relocate? Would some
of the other PPC32 platforms not require the cache flushing?
What I was suggesting is, instead of flushing the cache in relocate(), lets do
it
like:
for e.g, on 440x, (in head_44x.S :)
#ifdef CONFIG_RELOCATABLE
...
bl relocate
#Flush the d-cache and invalidate the i-cache here
#endif
This would let the different platforms do the the cache invalidation in their
own way.
Btw, I didn't find an instruction to flush the entire d-cache in PPC440 manual.
We have instructions to flush only a block corresponding to an address.
However, we have 'iccci' which would invalidate the entire i-cache which, which
I think is better than 80,000 i-cache invalidates.
Kumar / Josh,
Do you have any suggestions here ?
My PPC32 knowledge is 4xx-centric, so please feel free to rewrite the
patch as needed to accommodate other PPC32 cores.
Same here :)
Thanks
Suzuki
_______________________________________________
Linuxppc-dev mailing list
Linuxppc-dev@lists.ozlabs.org
https://lists.ozlabs.org/listinfo/linuxppc-dev
