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

[Tuomas Tynkkynen]

Hi Alexander,

On Thu, 24 May 2018 10:12:54 +0200
Alexander Graf <agraf at suse.de> wrote:

> 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?

I believe fdt_addr is what is passed to the kernel and fdt_blob is what
U-Boot's device model is using.

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

Good.

> 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.

Makes sense, but I guess needs some documentation. Also for existing things
like whether enable_uart=1 is needed or not.

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

Thanks,
Tuomas