[U-Boot] [PATCH] rpi: Adjust fdt_addr_r to a sane address

[Alexander Graf]

On 14.04.18 20:04, Tuomas Tynkkynen wrote:
> Hi Alexander,
> 
> On Fri, 13 Apr 2018 17:49:00 +0200
> Alexander Graf <agraf at suse.de> wrote:
> 
> [...]
>>
>> diff --git a/include/configs/rpi.h b/include/configs/rpi.h
>> index 325e52a019..fcf7e0976b 100644
>> --- a/include/configs/rpi.h
>> +++ b/include/configs/rpi.h
>> @@ -124,7 +124,7 @@
>>  #define ENV_MEM_LAYOUT_SETTINGS \
>>  	"fdt_high=ffffffff\0" \
>>  	"initrd_high=ffffffff\0" \
>> -	"fdt_addr_r=0x00000100\0" \
>> +	"fdt_addr_r=0x01f00000\0" \
>>  	"pxefile_addr_r=0x00100000\0" \
>>  	"kernel_addr_r=0x01000000\0" \
>>  	"scriptaddr=0x02000000\0" \
> 
> Note that above the #define is a larger comment block that needs to be
> updated as well. Also the other addresses also need updatingfor bigger
> kernels on AArch64: https://patchwork.ozlabs.org/patch/777725/
> 
> Though now I double-checked that the smallest possible GPU-CPU memory
> split is actually 64MB for the CPU, not 128M. So maybe something like:
> 
>          "kernel_addr_r=0x00080000\0" \
>          "fdt_addr_r=0x02400000\0" \
>          "scriptaddr=0x02500000\0" \
>          "pxefile_addr_r=0x02600000\0" \
>          "ramdisk_addr_r=0x02700000\0"
> 
> which would allow a kernel up to 36M, 1M for dtb, script and pxe files
> each, and at least 25M for the initrd. Also I think giving up with the
> constraint of locating the zImage high enough so that the kernel
> decompressor doesn't need to relocate itself can be dropped. If the
> boot speed of their Raspi matters that much, probably they wouldn't use
> U-Boot in the first place.
> 
> What is the address that the RPi firmware loads its device tree to? I
> hope that we don't have to worry about the positioning of that too...

U-Boot> bdinfo
arch_number = 0x00000000
boot_params = 0x00000100
DRAM bank   = 0x00000000
-> start    = 0x00000000
-> size     = 0x3B400000
baudrate    = 115200 bps
TLB addr    = 0x3B3F0000
relocaddr   = 0x3B348000
reloc off   = 0x3B2C8000
irq_sp      = 0x3AF3E120
sp start    = 0x3AF3E120
Early malloc usage: 138 / 2000
fdt_blob = 000000003af3e130
U-Boot> print fdt_addr
fdt_addr=2effb300

So on boot the DT passed into U-Boot is either at ~750MB or close to the
top. I can't quite find any code that explains the difference in the two
variables. Either way, I guess firmware tries to put it reasonably high?

So as long as we keep the load addresses low enough, we should be safe.

Also fyi, I would like to switch to CONFIG_OF_BOARD by default, once I
added code that marks u-boot.bin as an "upstream kernel" for the RPi
firmware, because then newer RPi firmwares will pass us a fully upstream
compatible device tree [1] which we can then pass on to Linux as default.


Alex

[1] https://github.com/raspberrypi/firmware/issues/943