Hello Hans,
On Tue, 20 Jan 2015 15:32:34 +0100, Hans de Goede hdegoede@redhat.com wrote:
Hi,
On 20-01-15 11:22, Albert ARIBAUD wrote:
Hello Hans,
I'm leaning toward grouping all CP15 inits (including cache(s) and TLB disabling and maybe VBAR setting) in a single CP15 call to a single soc_init_cp15 function.
Now, SoCs with the same CPU will have a common CP15 init part, and that part could go into a <cpu>_init_cp15 function which soc_init_cp15 would call. Of course, since we're doing this way before we have any stack, we will have to handle nested calls by saving and restoring LR in intermediate function contexts.
Note that solving this still leaves the A80 magic sram controller poke which also needs to happen really really early or otherwise the entire SoC just resets as if the watchdog has triggered, I'm fine with using save_boot_params for that, it is not its intended purpose, but it works fine for it, so I see no reason to complicate things with yet another callback.
Maybe we could turn soc_init_cp15 into a more general soc_init function which would do whatever is needed, on cp15 or otherwise.
(I see there is one soc_init defined, for spear600, but it is actually empty and could/should be removed. Patch anyone?)
Hmm, so if I'm reading the above correctly, then I think you want to do the following:
- Rename cpu_init_cp15 to cpu_init_cp15_common
- Add a new soc_init function, with a weak default which just calls cpu_init_cp15_common
- Add a a7_init_cp15 which sets the smp bit
- Have Cortex A7 SoCs override soc_init with one which first calls a7_init_cp15 and then calls cpu_init_cp15_common
- And on SoC's which need to do something special before or after cp15 init, they can do so by overriding soc_init and do what ever they need to do there before *or* after calling cpu_init_cp15_common
Have I got that right ?
Almost entirely. My only comments are on 1) :
- cpu_init_cp15_common does not need the "common" suffix IMO; actually, it might be more general than just touching cp15, so we could just call it "cpu_init" (1).
- if two CPUs need different versions, then we will want to make cpu_init a weak function, with a default based on the 'common denominator'.
(1) Note that there is already a cpu_init() function in U-Boot, used by SH and AVR32; if we want 'cpu_init' to be consistent across architectures, we might have to change "{soc,cpu}_init" to somehting else (for instance "{soc,cpu}_setup" or "{soc,cpu}_boot_init") but I don't like that much, or investigate what the existing cpu_init() does and see if /that/ could be renamed or merged into a common mechanism (I doubt that the second is practically feasible).
If so I can try to write a patch-set for this, my arm asm is a bit weak, but I should be able to cobble this together using existing code as an example.
Thanks!
Regards,
Hans
Amicalement,