/*
* Represent all available RAM in either one or two banks.
*
* The first bank describes any usable RAM below 4GiB.
* The second bank describes any RAM above 4GiB.
*
* This split is driven by the following requirements:
* - The NVIDIA L4T kernel requires separate entries in the DT /memory/reg
* property for memory below and above the 4GiB boundary. The layout of that
* DT property is directly driven by the entries in the U-Boot bank array.
* - The potential existence of a carve-out at the end of RAM below 4GiB can
* only be represented using multiple banks.
*
* Explicitly removing the carve-out RAM from the bank entries makes the RAM
* layout a bit more obvious, e.g. when running "bdinfo" at the U-Boot
* command-line.
*
* This does mean that the DT U-Boot passes to the Linux kernel will not
* include this RAM in /memory/reg at all. An alternative would be to include
* all RAM in the U-Boot banks (and hence DT), and add a /memreserve/ node
* into DT to stop the kernel from using the RAM. IIUC, I don't /think/ the
* Linux kernel will ever need to access any RAM in* the carve-out via a CPU
* mapping, so either way is acceptable.
*
* On 32-bit systems, we never define a bank for RAM above 4GiB, since the
* start address of that bank cannot be represented in the 32-bit .size
* field.
*/
void dram_init_banksize(void)
{
gd->bd->bi_dram[0].start = CONFIG_SYS_SDRAM_BASE;
gd->bd->bi_dram[0].size = usable_ram_size_below_4g();
#ifdef CONFIG_PCI
gd->pci_ram_top = gd->bd->bi_dram[0].start + gd->bd->bi_dram[0].size;
#endif
#ifdef CONFIG_PHYS_64BIT
if (gd->ram_size > SZ_2G) {
gd->bd->bi_dram[1].start = 0x100000000;
gd->bd->bi_dram[1].size = gd->ram_size - SZ_2G;
} else
#endif
{
gd->bd->bi_dram[1].start = 0;
gd->bd->bi_dram[1].size = 0;
}
}
/*
* Most hardware on 64-bit Tegra is still restricted to DMA to the lower
* 32-bits of the physical address space. Cap the maximum usable RAM area
* at 4 GiB to avoid DMA buffers from being allocated beyond the 32-bit
* boundary that most devices can address. Also, don't let U-Boot use any
* carve-out, as mentioned above.
*
* This function is called before dram_init_banksize(), so we can't simply
* return gd->bd->bi_dram[1].start + gd->bd->bi_dram[1].size.
*/
ulong board_get_usable_ram_top(ulong total_size)
{
return CONFIG_SYS_SDRAM_BASE + usable_ram_size_below_4g();
}
