Wolfgang Denk wrote:
First of all, current CONFIG_MIPS32 defines are useless. We can even remove them. What is fine granularity for, huh?
Why are these useless?
There is no user of this config, we can even remove these all.
[btw tb0229 is not MIPS32 at all. it's VR4131 based machine.]
Please excuse my ignorance - but I thought the VR4131 was a 32 bit MIPS based processor. Is this understanding incorrect?
All VR41XX processors are 32/64-bit capable. In this case it just runs in 32-bit mode. What's important is that VR41XX is MIPS III ISA [1].
And in cases where saying MIPS32, it usually means MIPS32 ISA. It's MIPS32(R) Arhchitecture [2].
[1] http://www.linux-mips.org/wiki/NEC_VR4100 [2] http://www.mips.com/products/processors/architectures/mips32/
See also [3] http://www.linux-mips.org/wiki/Instruction_Set_Architecture
The binaries compiled for MIPS32 might work on VR41XX machines (I'm not sure. usually we don't do that.), but that's not my point.
And why I use CONFIG_CPU_MIPS32_R1, instead of CONFIG_CPU_MIPS32, is due to avoiding #ifdef mess. CONFIG_CPU_MIPS32 is inadequate for this use.
Where is such #ifdef mess supposed to happen? Do you refer to existing code, or anything you are going to add?
The latter.
Well, yes - if it's for compiler/assembler options only, then the board config file is not the correct place for this.
I don't think so because 1) CPU type is not board-dependent, and 2) the board config file is not board-specific file, but system config file. CPU type is reasonably one of system configuration, IMO.
And these CPU type specifiers are not only used for compiler/assembler optimization, but also is useful when categorizing processor specific routines. For example, Linux is doing like this:
[arch/mips/mm/Makefile] obj-$(CONFIG_CPU_MIPS32) += c-r4k.o cex-gen.o tlb-r4k.o obj-$(CONFIG_CPU_TX39XX) += c-tx39.o tlb-r3k.o
In accordance with above, we can do like this:
[cpu/mips/Makefile] SOBJS-$(CONFIG_CPU_MIPS32) += cache-mips32.o SOBJS-$(CONFIG_CPU_VR41XX) += cache-vr41xx.o
Unfortunately current cache routines doesn't work for all NEC VR-series processors at all. I'll fix in the future.
At last I have to mention about CPU type specifiers. These specifiers are neigher MIPS Processor ID (PRId) nor gcc -march option alternatives. These are virtual options designed for organizing various MIPS options, routines, and object selections of Makefile. They're defined in Kconfig.
I think these are exactly good granularity, and like to see them in U-Boot system configuration, too.
Shinya
P.S. I decided to defer this patch due to some reason. That's another story and will inform the list later.