Hi Simon,
On Mon, Dec 5, 2016 at 7:24 AM, Simon Glass sjg@chromium.org wrote:
Hi,
On 1 December 2016 at 01:39, Stefan Roese sr@denx.de wrote:
(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@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
Can you add documentation for this somewhere? E.g. in the driver model readme?
OK, I'll document the feature in v2.
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"helpIn certain circumstances it is necessary to be able to modifyU-Boot's device tree (e.g. to delete device from it). Thisoption
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. Themodified 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
Can we keep it as const and just use a cast when it needs to change? You could add a function which returns a writable pointer.
Having the pointer globally writable has the advantage that you can get a writable pointer wherever you need it and don't have to pass it around, but separating the parts where the pointer is writable from the ones where it is not is probably a good idea. Will fix in v2.
void *new_fdt; /* Relocated FDT */ unsigned long fdt_size; /* Space reserved for relocatedFDT */ 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);
Comment please. Perhaps it should pass a writable fdt pointer?
I'll add a comment in v2.
int board_late_init (void); int board_postclk_init (void); /* after clocks/timebase, before env/serial */ int board_early_init_r (void);
There have been discussions about moving to a live tree (hierarchical format) in U-Boot post-relocation. What do you think? It might make these changes easier or more efficient.
Yes, that would definitely make things easier. The approach of modifying the tree before the main U-Boot "sees it" that I'm taking here seems a bit hacky. The other approach I've been experimenting with consisted of starting the board with a base device tree, which only has the devices in it that are guaranteed to exists, gather all needed data to decide which overlays to apply, then tear down the DM (using dm_uninit), make the modifications to the tree, and restart the DM (with dm_init_and_scan). While this worked more or less fine, it seems very wasteful, and a genuinely modifiable tree would be a much nicer solution.
Also, we need a solution to this problem one way or another; the way our hardware is constructed, we need to check which devices actually exist and which do not by querying the hardware itself. And the most natural thing to do here would be to have a modifiable device tree.
Regards, Simon