[U-Boot] [PATCH] remove (double) LED initialization in arm920t start.s
* remove LED initialization in front of relocation and bss init
Signed-off-by: Jens Scharsig js_at_ng@scharsoft.de ---
* prevents run C function on an uninitialized environment
arch/arm/cpu/arm920t/start.S | 3 --- 1 files changed, 0 insertions(+), 3 deletions(-)
diff --git a/arch/arm/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S index 08f178d..764a06a 100644 --- a/arch/arm/cpu/arm920t/start.S +++ b/arch/arm/cpu/arm920t/start.S @@ -119,9 +119,6 @@ start_code: orr r0, r0, #0xd3 msr cpsr, r0
- bl coloured_LED_init - bl red_LED_on - #if defined(CONFIG_AT91RM9200DK) || defined(CONFIG_AT91RM9200EK) /* * relocate exception table -- 1.7.1
Dear Jens Scharsig,
Am 18.12.2010 um 13:08 schrieb Jens Scharsig:
- remove LED initialization in front of relocation and bss init
Signed-off-by: Jens Scharsig js_at_ng@scharsoft.de
- prevents run C function on an uninitialized environment
You are right, we do not have stack/bss setup when we call these two c-functions.
But in that case it is ok to do so cause we do just pc relative accesses here, do not use bss variables and last we do not use the stack.
Beside the fact that we could use it here as it is done since atmel posted their at91rm9200 code we could ask if we need it or not.
I think it is a nice helper for initialisation debugging and I used it from time to time for my relocation investigations. But I think we do _not_ need it in every arm920t/at91 board for every bootup. It should be a) enclosed in some ifdef to enable them conditionally on compile time b) documented in a README and completely removed (some lines later too)
Beside that one could state c) completely removed (the whole coloured_LED stuff) as this is atmel specific and other SoC use another interface to switch LED if we decide to not use these LED features for bootup debugging.
AFAIK this is also used in arm926ejs (at91sam only), Reinhard can you please comment on that?
regards
Andreas Bießmann
On 23.12.2010 12:58, Andreas Bießmann wrote:
Dear Jens Scharsig,
Am 18.12.2010 um 13:08 schrieb Jens Scharsig:
- remove LED initialization in front of relocation and bss init
Signed-off-by: Jens Scharsigjs_at_ng@scharsoft.de
- prevents run C function on an uninitialized environment
You are right, we do not have stack/bss setup when we call these two c-functions.
But in that case it is ok to do so cause we do just pc relative accesses here, do not use bss variables and last we do not use the stack.
Beside the fact that we could use it here as it is done since atmel posted their at91rm9200 code we could ask if we need it or not.
I think it is a nice helper for initialisation debugging and I used it from time to time for my relocation investigations. But I think we do _not_ need it in every arm920t/at91 board for every bootup. It should be a) enclosed in some ifdef to enable them conditionally on compile time b) documented in a README and completely removed (some lines later too)
Beside that one could state c) completely removed (the whole coloured_LED stuff) as this is atmel specific and other SoC use another interface to switch LED if we decide to not use these LED features for bootup debugging.
AFAIK this is also used in arm926ejs (at91sam only), Reinhard can you please comment on that?
Quite funny, incidentally right this morning I tried to figure out how to use LEDs to assist a "blackbox" sort of system that has only 3 RG LEDs to signal u-boot phases and errors before kernel and application are ultimately started.
This part of u-boot is quite messy, look at "status_led.h" for example...
I agree the AT91 colored LED specialty should be removed, once we can agree on a useful common LED approach.
And I think that should be working the other way. It is pointless to try to factorize it into a few LEDs with specific meanings.
We should have one function like "show_status(int status)" with various statuses defined like: LED_STATUS_RESET, _BEFORE_RELOC, _AFTER_RELOC, _SENT_DHCP, _STARTING_KERNEL, _CRASHED, ...
Then it is up to the board specific code to drive multicolored LEDs, an LCDisplay, some seven-segment displays or even relais.
But I guess that's too futuristic, and as always there is a lot of existing code that does it in various different ways :(
Best Regards, Reinhard
Dear Reinhard Meyer,
In message 4D1340BD.2090206@emk-elektronik.de you wrote:
We should have one function like "show_status(int status)" with various statuses defined like: LED_STATUS_RESET, _BEFORE_RELOC, _AFTER_RELOC, _SENT_DHCP, _STARTING_KERNEL, _CRASHED, ...
Keep the existing code, and just turn the current set of numbers into an enum.
Best regards,
Wolfgang Denk
Dear Wolfgang Denk,
Dear Reinhard Meyer,
In message4D1340BD.2090206@emk-elektronik.de you wrote:
We should have one function like "show_status(int status)" with various statuses defined like: LED_STATUS_RESET, _BEFORE_RELOC, _AFTER_RELOC, _SENT_DHCP, _STARTING_KERNEL, _CRASHED, ...
Keep the existing code, and just turn the current set of numbers into an enum.
What current code?
1. show_boot_progress() is quite close, but has hundreds of values... Not sure a enum would be useful there, the values have gaps; rather an errno.h like implementation makes sense there.
2. the LED current code (in some non-ARM) places has LED types (BOOT, ...) and LED modes (OFF, BLINK, ON). That is totally different and quite useless for seven segment and simple LCDisplays.
Best Regards, Reinhard
Dear Reinhard Meyer,
In message 4D134C08.8090609@emk-elektronik.de you wrote:
Keep the existing code, and just turn the current set of numbers into an enum.
What current code?
I meant the existing show_boot_progress() code.
- show_boot_progress() is quite close, but has hundreds of values...
Not sure a enum would be useful there, the values have gaps; rather an errno.h like implementation makes sense there.
I think it's just an implementation detail wether you use an enum or #defines here.
- the LED current code (in some non-ARM) places
has LED types (BOOT, ...) and LED modes (OFF, BLINK, ON). That is totally different and quite useless for seven segment and simple LCDisplays.
Right.
Note that there is more code when it comes to seven segment and character based LCD displays - please see doc/README.LED_display, include/led-display.h, common/cmd_display.c and drivers/misc/pdsp188x.c on one side, or the highly board specific display code using the same framework in board/a4m072/a4m072.c on the other side.
Best regards,
Wolfgang Denk
To explain the background
1st:
I've compiled my code for easier debugging without -Os option. But the non optimized code needs a valid stack at this position. It's only as secondary problem
2nd:
The functions will called later again.
3rd:
Some soc are not fully intitialized here (e.g Clock aso). So, we also increase the boot speed.
regards
Jens
Le 18/12/2010 13:08, Jens Scharsig a écrit :
- remove LED initialization in front of relocation and bss init
Signed-off-by: Jens Scharsigjs_at_ng@scharsoft.de
- prevents run C function on an uninitialized environment
arch/arm/cpu/arm920t/start.S | 3 --- 1 files changed, 0 insertions(+), 3 deletions(-)
diff --git a/arch/arm/cpu/arm920t/start.S b/arch/arm/cpu/arm920t/start.S index 08f178d..764a06a 100644 --- a/arch/arm/cpu/arm920t/start.S +++ b/arch/arm/cpu/arm920t/start.S @@ -119,9 +119,6 @@ start_code: orr r0, r0, #0xd3 msr cpsr, r0
- bl coloured_LED_init
- bl red_LED_on
- #if defined(CONFIG_AT91RM9200DK) || defined(CONFIG_AT91RM9200EK) /*
- relocate exception table
-- 1.7.1
Applied to U-boot-arm, thanks.
Amicalement,
participants (5)
-
Albert ARIBAUD -
Andreas Bießmann -
Jens Scharsig -
Reinhard Meyer -
Wolfgang Denk