[U-Boot] decode_regions() function

[Simon Glass]

Hi York,

On 8 February 2017 at 14:58, york sun <york.sun at nxp.com> wrote:
> 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?

It is assuming a simple contiguous memory setup. If it is not
contiguous then it isn't right. It would need to add several regions,
I suppose.

Regards,
Simon