Re: [RFT PATCH] ARM64: dts: meson-gxbb: Add reserved memory zone and usable memory range

From: Neil Armstrong
Date: Mon Jan 16 2017 - 05:27:07 EST


On 01/15/2017 04:44 PM, Andreas Färber wrote:
> Am 23.12.2016 um 10:42 schrieb Heinrich Schuchardt:
>> it really makes a difference if we write
>>
>> memory@0 {
>> device_type = "memory";
>> linux,usable-memory = <0x0 0x1000000 0x0 0x7f000000>;
>> };
>>
>> or
>>
>> memory@0 {
>> device_type = "memory";
>> reg = <0x0 0x1000000 0x0 0x7f000000>;
>> };
>>
>> The second version leads to failure of the Odroid C2.
>>
>> When I looked at /sys/firmware/fdt I saw this difference:
>>
>> --- fails
>> +++ works
>>
>> memory@0 {
>> - device_type = "memory";
>> reg = <0x0 0x0 0x0 0x78000000>;
>> + device_type = "memory";
>> + linux,usable-memory = <0x0 0x1000000 0x0 0x7f000000>;
>> };
>>
>> I found the following sentence in the NXP forum:
>> In case you want to overwrite the memory usage passed from u-boot, you
>> can use "linux,usable-memory".
>> https://community.nxp.com/thread/382284
>
> The Odroid-C2 is in mainline U-Boot. Please submit a patch to U-Boot
> instead of forcing the creation of unnecessary new .dts files onto
> everyone due to hardcoded linux,usable-memory properties. In fact, it
> already reserves 0x1000000, so it seems you are merely using an older
> U-Boot.
>
> http://git.denx.de/?p=u-boot.git;a=blob;f=arch/arm/mach-meson/board.c;h=f159cbf849f75ab046e6f3a025bbc97c0bcfd59d;hb=HEAD#l39
>
> I would bet that the upper limit is unrelated here.
>
> Regards,
> Andreas
>

Hi Andreas,

I really disagree about relying on any work or properties added by any bootloader here, Amlogic SoCs has
a lot of u-boot version in the field, and the Odroid-C2 is part of this.

Even if Odroid-c2 is in mainline U-Boot or not, the mainline Linux kernel should work using
any U-boot version even with the one provided by Amlogic on their openlinux distribution channel.

Neil