dcache on ARM
cover dcache on ARM
These patches enable the dcache for ARM9. It's mainly an RFC, as some details are still to be sorted out, but they work fine (and the speed increase is noticeable for kernel boots and cp.b -- didn't make more tests.
I tested the code on at91sam9263ek and nhk8815. No makeall at this point, as I'm mainly interested in comments here.
This is based on the cache-cp15.c infrastructure set up by Jean-Christophe for icache enabling.
I'm sure Drasko Draskovic has better code, but since he has sent no a patch yet (asked in Mar 2009, and then again and again), here is my approach.
Alessandro Rubini (2):
flush cache for arm926
arm cp15: setup mmu and enable dcache
lib_arm/cache-cp15.c | 37 +++++++++++++++++++++++++++++++++++++ lib_arm/cache.c | 6 ++++++ 2 files changed, 43 insertions(+), 0 deletions(-)
cover dcache on ARM
Quoted 4 lines · Alessandro Rubini
These patches enable the dcache for ARM9. It's mainly an RFC, as some details are still to be sorted out, but they work fine (and the speed increase is noticeable for kernel boots and cp.b -- didn't make more tests.
I'm all for speed increases :-)
On TI DA830, the 1.0 & 1.1 revision of the silicon have a data caching bug. You can use data caching, but only in write thru' mode. This is fixed in the very latest 2.0 silicon. Even still it is better than no caching as proved in Linux.
Is it simple for you to enable different levels of caching by config?
Nick.
cover dcache on ARM
Hello Nick.
Quoted 2 lines
On TI DA830, the 1.0 & 1.1 revision of the silicon have a data caching bug. You can use data caching, but only in write thru' mode.
I see. So instead of both C and B you just need to C bit set in the page table, and no B.
I propose to allow an extra option for write-back, leaving write-through as the default. This matches the blackfin, which has CONFIG_DCACHE_WB as an option, and leaves a safer default for those who won't explicitly require WB policy.
Could you please confirm my patch works on that board after changing the magic bits from 0x1e to 0x1a ? (I'll use symbolic constants anyways in V2, this was just a quick RFC to see if the approach is acceptable).
/alessandro
cover dcache on ARM
In reply to Alessandro RubiniAlessandro,
I don't see the flush_cache() call inside cmd_bootm.c. Don't you think it is necessary before jumping to Linux? Or am I missing something?
Rgds,
Arm
Quoted 27 lines · Alessandro Rubini
These patches enable the dcache for ARM9. It's mainly an RFC, as some details are still to be sorted out, but they work fine (and the speed increase is noticeable for kernel boots and cp.b -- didn't make more tests.
I tested the code on at91sam9263ek and nhk8815. No makeall at this point, as I'm mainly interested in comments here.
This is based on the
cache-cp15.cinfrastructure set up by Jean-Christophe for icache enabling.I'm sure Drasko Draskovic has better code, but since he has sent no a patch yet (asked in Mar 2009, and then again and again), here is my approach.
Alessandro Rubini (2):
flush cache for arm926
arm cp15: setup mmu and enable dcachelib_arm/cache-cp15.c | 37 +++++++++++++++++++++++++++++++++++++ lib_arm/cache.c | 6 ++++++ 2 files changed, 43 insertions(+), 0 deletions(-)_______________________________________________
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Signature · 8 lines
-- "Every step appears to be the unavoidable consequence of the -- preceding one." (A. Einstein) -- Armando Visconti Mobile: (+39) 346 8879146 Senior SW Engineer Fax: (+39) 02 93519290 CPG Work: (+39) 02 93519683 Computer System Division e-mail: armando.visconti at st.com ST Microelectronics TINA: 051 4683
cover dcache on ARM
Quoted 2 lines
I don't see the
flush_cache()call insidecmd_bootm.c. Don't you think it is necessary before jumping to Linux?
Yes, definitely. Actually, I checked it, but re-checking now I see I've been tricked by '[id]cache_disable' being grepped successfully in common/cmd_bootm.c . However, it's inside a false ifdef.
I'm booting through the network, so that's probably why it works reliably for me (netboot_common does the propre flushing).
Quoted 1 line
Or am I missing something?
Not at all, thanks for catching this.
/alessandro
cover dcache on ARM
Quoted 5 lines
Quoted 4 lines
I don't see the
flush_cache()call insidecmd_bootm.c. Don't you think it is necessary before jumping to Linux?
Quoted 7 lines
Yes, definitely. Actually, I checked it, but re-checking now I see I've been tricked by '[id]cache_disable' being grepped successfully in
common/cmd_bootm.c. However, it's inside a false ifdef.I'm booting through the network, so that's probably why it works reliably for me (
netboot_commondoes the propre flushing).
Right, cache_disable() should be called to do the proper job, i.e. cache disabling and flushing.
OK, we can wait for more comments but if there are no other architectural drawbacks I can't think of I'm willing to test it on
SPEAr achitecture as well. Actually I have always thought about enabling dcache, but too lazy to implement/verify it :-(
Thx,
Arm
Signature · 8 lines
-- "Every step appears to be the unavoidable consequence of the -- preceding one." (A. Einstein) -- Armando Visconti Mobile: (+39) 346 8879146 Senior SW Engineer Fax: (+39) 02 93519290 CPG Work: (+39) 02 93519683 Computer System Division e-mail: armando.visconti at st.com ST Microelectronics TINA: 051 4683