[U-Boot] decode_regions() function

[york sun]

Simon,

I stumped on this issue when I was rewriting the code to reserve secure 
memory. I didn't realize gd->ram_size was used in the driver. I made the 
top of memory secure so EL2 code wouldn't be able to access. All of the 
sudden my PCI device failed. By reducing the gd->ram_size, PCI works again.

Can you help me to understand a function in drivers/pci/pci-uclass.c? 
Around line 818 in function

static int decode_regions(struct pci_controller *hose, const void *blob,
                           int parent_node, int node)


         /* Add a region for our local memory */
         size = gd->ram_size;
#ifdef CONFIG_SYS_SDRAM_BASE
         base = CONFIG_SYS_SDRAM_BASE;
#endif
         if (gd->pci_ram_top && gd->pci_ram_top < base + size)
                 size = gd->pci_ram_top - base;
         pci_set_region(hose->regions + hose->region_count++, base, base,
                        size, PCI_REGION_MEM | PCI_REGION_SYS_MEMORY);


What would happen if pci_ram_top is not set, and the memory is split 
into banks? gd->ram_size would have the total memory, but not in 
continuous space. Is adding a single region correct here?

York