Dear Macpaul Lin,
Please keep the mailing list on Cc: (re-added)
In message AANLkTinYJhoGrA7ZAVUQxwByrkWNqomCBFWiJG_+3+0e@mail.gmail.com you wrote:
I repeat again: I consider this manual unrolling of the nested structs a Bad Thing. You should have separate offsets for each of the nested structs.
The above code is really a rework for a nested structs. The origin code looks like, Moreover, the structure of ftsmc020 was nested like struct ftsmc020 { struct { unsigned int cr; /* 0x00, 0x08, 0x10, 0x18 */ unsigned int tpr; /* 0x04, 0x0c, 0x14, 0x1c */ } bank[4]; unsigned int pad[8]; /* 0x20 - 0x3c */ unsigned int ssr; /* 0x40 */ }
After rewrote it becomes struct ftsmc020 { unsigned int bank0_cr; unsigned int bank0_tpr; unsigned int bank1_cr; unsigned int bank1_tpr; unsigned int bank2_cr; unsigned int bank2_tpr; unsigned int bank3_cr; unsigned int bank3_tpr; unsigned int pad[8]; unsigned int ssr; }
Did I misunderstand what you exactly meant?
Yes, indeed. Unnesting means to move the inner struct declaration outside, like that:
struct ftsmc020_bank { unsigned int cr; unsigned int tpr; };
struct ftsmc020 { struct ftsmc020_bank bank[4]; unsigned int pad[8]; unsigned int ssr; };
Again: if you need larger numbers of such entries you are doing something fundamentally wrong. Reconsider your coding style. What exactly enforces you to use assembly?
This is because writing assembly code (lowlevel_init) is really a necessity for setting the timing and power outpur correctly to these registers (SMC, SDMC, PMU).
What exactly prevents you from writing the very same code in C?
It is required to give a correct setting to PMU and SMC to make the onboard DRAM works correctly before the code is loaded from ROM to DRAM and then set up stack for C environemnt.
We take care to provide global data and an initial stack very, very early in the initialization sequence. You canuse C code long before you can access the system RAM.
Hence assembly code to setting SMC and PMU in lowlevel_init is a necessity
I seriously doubt that. Just because many boards are writen that way does not mean that's how it must be done - actualy many just copied existing bad examples without thinking.
Best regards,
Wolfgang Denk