Re: [U-Boot] Dynamically determine RAM size and pass it to kernel

On 17.11.2016 15:09, Mike Looijmans wrote:

On 17-11-16 13:34, Mike Looijmans wrote:

...

We have some Zynq based boards still in the field that have only 512MB RAM instead of 1GB. The memory chips are compatible and use the same settings apart from that one extra address bit.

So what works is just configure the DDR controller for 1GB and then check if writing some data "wraps" back, this is my "spike" code in the RAM init code for that:

•   u32 *ptr_1 = (u32*)0x10000;
  

•   u32 *ptr_2 = (u32*)((gd->ram_size >> 1) + 0x10000);
  

•   puts("RAM test");
  

•   *ptr_1 = 0x12345678;
  

•   if (*ptr_2 == *ptr_1) {
  

•           *ptr_1 = 0x87654321;
  

•           if (*ptr_2 == *ptr_1) {
  

•                   puts(" [HALF]");
  

•                   gd->ram_size >>= 1;
  

•           }
  

•   }
  

I found that I can replace that with "get_mem_size()" which does this better.

You have some ways. 1. Rewrite dram_init() function to run this test. 2. Let SPL find out and add two dtbs to it. IIRC board_fit_config_name_match() is that function which can decide that. 3. If you use module, look at spd eeprom and read it which is something what I was playing with on zcu102. Freescale boards in past used this a lot.

Thanks, Michal