[U-Boot] [PATCH 06/17] dm: Add callback to modify the device tree

[Stefan Roese]

(Adding Simon and Maxim to Cc)

On 23.11.2016 16:12, Mario Six wrote:
> Certain boards come in different variations by way of utilizing daughter
> boards, for example. These boards might contain additional chips, which
> are added to the main board's busses, e.g. I2C.
>
> The device tree support for such boards would either, quite naturally,
> employ the overlay mechanism to add such chips to the tree, or would use
> one large default device tree, and delete the devices that are actually
> not present.
>
> Regardless of approach, even on the U-Boot level, a modification of the
> device tree is a prerequisite to have such modular families of boards
> supported properly.
>
> Therefore, we add an option to make the U-Boot device tree (the actual
> copy later used by the driver model) writeable, and add a callback
> method that allows boards to modify the device tree at an early stage,
> at which, hopefully, also the application of device tree overlays will
> be possible.
>
> Signed-off-by: Mario Six <mario.six at gdsys.cc>

I didn't follow DT overlay lately closely especially not in U-Boot.
Simon, Maxim could you please take a look at this patch and comment
on its necessity?

> ---
>  common/board_f.c                  |  3 +++
>  dts/Kconfig                       | 10 ++++++++++
>  include/asm-generic/global_data.h |  4 ++++
>  include/common.h                  |  1 +
>  4 files changed, 18 insertions(+)
>
> diff --git a/common/board_f.c b/common/board_f.c
> index 4b74835..cda5aae 100644
> --- a/common/board_f.c
> +++ b/common/board_f.c
> @@ -1034,6 +1034,9 @@ static init_fnc_t init_sequence_f[] = {
>  #ifdef CONFIG_SYS_EXTBDINFO
>  	setup_board_extra,
>  #endif
> +#ifdef CONFIG_OF_BOARD_FIXUP
> +	board_fix_fdt,
> +#endif
>  	INIT_FUNC_WATCHDOG_RESET
>  	reloc_fdt,
>  	setup_reloc,
> diff --git a/dts/Kconfig b/dts/Kconfig
> index 4b7d8b1..3f64eda 100644
> --- a/dts/Kconfig
> +++ b/dts/Kconfig
> @@ -14,6 +14,16 @@ config OF_CONTROL
>  	  This feature provides for run-time configuration of U-Boot
>  	  via a flattened device tree.
>
> +config OF_BOARD_FIXUP
> +	bool "Board-specific manipulation of Device Tree"
> +	help
> +	  In certain circumstances it is necessary to be able to modify
> +	  U-Boot's device tree (e.g. to delete device from it). This option
> +	  make the Device Tree writeable and provides a board-specific
> +	  "board_fix_fdt" callback (called during pre-relocation time), which
> +	  enables the board initialization to modifiy the Device Tree. The
> +	  modified copy is subsequently used by U-Boot after relocation.
> +
>  config SPL_OF_CONTROL
>  	bool "Enable run-time configuration via Device Tree in SPL"
>  	depends on SPL && OF_CONTROL
> diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
> index e02863d..f566186 100644
> --- a/include/asm-generic/global_data.h
> +++ b/include/asm-generic/global_data.h
> @@ -69,7 +69,11 @@ typedef struct global_data {
>  	struct udevice	*timer;		/* Timer instance for Driver Model */
>  #endif
>
> +#ifdef CONFIG_OF_BOARD_FIXUP
> +	void *fdt_blob;			/* Our device tree, NULL if none */
> +#else
>  	const void *fdt_blob;		/* Our device tree, NULL if none */
> +#endif
>  	void *new_fdt;			/* Relocated FDT */
>  	unsigned long fdt_size;		/* Space reserved for relocated FDT */
>  	struct jt_funcs *jt;		/* jump table */
> diff --git a/include/common.h b/include/common.h
> index a8d833b..293ce23 100644
> --- a/include/common.h
> +++ b/include/common.h
> @@ -502,6 +502,7 @@ extern ssize_t spi_write (uchar *, int, uchar *, int);
>
>  /* $(BOARD)/$(BOARD).c */
>  int board_early_init_f (void);
> +int board_fix_fdt (void);
>  int board_late_init (void);
>  int board_postclk_init (void); /* after clocks/timebase, before env/serial */
>  int board_early_init_r (void);
>

Thanks,
Stefan