[U-Boot] [PATCH] efi_loader: don't allocate unusable RAM

[Stephen Warren]

On 08/01/2018 12:07 AM, Heinrich Schuchardt wrote:
> On 07/31/2018 09:44 PM, Stephen Warren wrote:
>> From: Stephen Warren <swarren at nvidia.com>
>>
>> Some boards define a maximum usable RAM top that's more restrictive than
>> the ranges defined by U-Boot's memory bank definitions[1]. In this case,
>> the unusable RAM isn't mapped in the page tables, and so the EFI code must
>> not attempt to allocate RAM from outside the usable regions. Fix
>> efi_find_free_memory() to detect when max_addr is unconstrained or out of
>> range, and substitue a valid value.
>>
> 
> In this case the board has to call efi_add_memory_map() to mark the
> reserved region (cf. board/raspberrypi/rpi/rpi.c) or have to mark the
> memory region as reserved in the device tree (see efi_carve_out_dt_rsv()).
> 
> Please, check if the tegra boards with which you had problems do so.

I don't think this makes sense; memory should be managed the same way 
within U-Boot no matter which part of U-Boot is consuming that memory. 
Memory regions are currently represented by the content of the memory 
bank definitions and gd->ram_top. Having different parts of the code 
define legal RAM usage in different ways is horribly inconsistent.

At this point, I think the best thing is to revert aa909462d018 
"efi_loader: efi_allocate_pages is too restrictive" since it causes a 
regression on Jetson TX1, and we can work out the correct way to fix all 
this once the system is working again.