[U-Boot] [PATCH v2 24/29] riscv: store device tree passed by prior boot stage in environment

[Auer, Lukas]

On Tue, 2018-10-30 at 14:19 +0100, Alexander Graf wrote:
> 
> On 30.10.18 13:55, Lukas Auer wrote:
> > The device tree passed by the prior boot stage can be used to boot
> > Linux. Store it as environment variable "prior_stage_dtb", so that
> > it
> > can be used as part of the boot command.
> > 
> > Signed-off-by: Lukas Auer <lukas.auer at aisec.fraunhofer.de>
> > ---
> > 
> > Changes in v2:
> > - New patch
> > 
> >  arch/Kconfig                          | 1 +
> >  arch/riscv/cpu/cpu.c                  | 7 +++++++
> >  arch/riscv/include/asm/u-boot-riscv.h | 1 +
> >  3 files changed, 9 insertions(+)
> > 
> > diff --git a/arch/Kconfig b/arch/Kconfig
> > index 9fdd2f7e66..883e4a9308 100644
> > --- a/arch/Kconfig
> > +++ b/arch/Kconfig
> > @@ -74,6 +74,7 @@ config RISCV
> >  	imply MTD
> >  	imply TIMER
> >  	imply CMD_DM
> > +	imply ARCH_MISC_INIT
> >  
> >  config SANDBOX
> >  	bool "Sandbox"
> > diff --git a/arch/riscv/cpu/cpu.c b/arch/riscv/cpu/cpu.c
> > index d9f820c44c..e06a8c6bab 100644
> > --- a/arch/riscv/cpu/cpu.c
> > +++ b/arch/riscv/cpu/cpu.c
> > @@ -53,3 +53,10 @@ int print_cpuinfo(void)
> >  
> >  	return 0;
> >  }
> > +
> > +int arch_misc_init(void)
> > +{
> > +	env_set_hex("prior_stage_dtb", prior_stage_fdt_address);
> 
> Please reuse one of the many other variable names we have for this
> already, such as "fdtaddr".
> 

I will change the variable name.

> One thing I would always recommend is that if you have a prior stage
> DT
> passed on to U-Boot is that U-Boot makes use of that
> (CONFIG_OF_BOARD).
> That again means that the DT is already available in $fdtcontroladdr
> and
> there is very little use for yet another env variable.
> 
> 
> Alex
> 

We are actually using the device tree passed to U-Boot (using
CONFIG_OF_PRIOR_STAGE). The reason I'm adding the device tree address
to the environment is so that it can be used to boot Linux. RISC-V
Linux does not include any device trees, they are instead stored
directly on the SoC (though this might change). This is therefore
important to have and this is the best way I could think of, of
implementing it.

Thanks,
Lukas

> > +
> > +	return 0;
> > +}
> > diff --git a/arch/riscv/include/asm/u-boot-riscv.h
> > b/arch/riscv/include/asm/u-boot-riscv.h
> > index 49febd5881..937b2682dc 100644
> > --- a/arch/riscv/include/asm/u-boot-riscv.h
> > +++ b/arch/riscv/include/asm/u-boot-riscv.h
> > @@ -13,6 +13,7 @@
> >  
> >  /* cpu/.../cpu.c */
> >  int cleanup_before_linux(void);
> > +int arch_misc_init(void);
> >  
> >  /* board/.../... */
> >  int board_init(void);
> >