[PATCH v2 2/2] ARM: setup_c: avoid clearing BSS twice
Ahmad Fatoum
a.fatoum at pengutronix.de
Tue Mar 17 08:56:45 PDT 2026
Hello David,
On 3/17/26 1:43 PM, David Picard wrote:
> I tested from the last but one commit on master, but I don't think it's
> a big deal.
>
> Anyway, my board boots. Congrats!
I think you missed Sascha's patch at the end of his mail.
The change that has been dropped from next is a building block for a
boot time optimization and it would be very helpful to understand what
exactly broke at your side, so a revised patch can be applied.
To help with that, Sascha included a patch with some extra debug output.
Cheers,
Ahmad
>
> David
>
> Le 17/03/2026 à 10:06, Sascha Hauer a écrit :
>> Hi David,
>>
>> On Mon, Mar 16, 2026 at 02:21:37PM +0100, David Picard wrote:
>>> Hi,
>>>
>>> I would like this patches be reverted, since, despite the proposed
>>> fixes, it
>>> prevents the board arch/arm/boards/enclustra-sa2 to boot.
>> I reverted this patch for now, but nevertheless I'd like to understand
>> what's wrong with it.
>>
>>> With the option CONFIG_DEBUG_LL enabled, the output is:
>>>
>>> lowlevel init done
>>> SDRAM setup...
>>> SDRAM calibration...
>>> done
>>>
>>> Then, it hangs.
>> Could you apply the following patch to current master and see what the
>> output is?
>>
>> Thanks
>> Sascha
>>
>> ----------------------------------8<-----------------------------------
>>
>> From b784bc80756d127ae4a824ad235d4e113d5dcc1f Mon Sep 17 00:00:00 2001
>> From: Sascha Hauer <s.hauer at pengutronix.de>
>> Date: Wed, 4 Mar 2026 08:53:22 +0100
>> Subject: [PATCH] ARM: setup_c: avoid clearing BSS twice
>>
>> Add a bss_cleared variable that is set after the first call to
>> setup_c(). On subsequent calls, the BSS clear is skipped to avoid
>> wiping already-initialized data.
>>
>> Co-Authored-By: Claude Opus 4.6 <noreply at anthropic.com>
>> Reviewed-by: Ahmad Fatoum <a.fatoum at pengutronix.de>
>> Link: https://lore.barebox.org/20260304-arm-setup-c-v2-2-
>> d26af520ab03 at pengutronix.de
>> Signed-off-by: Sascha Hauer <s.hauer at pengutronix.de>
>> ---
>> arch/arm/cpu/setupc_32.S | 16 ++++++++++++++--
>> arch/arm/cpu/setupc_64.S | 15 +++++++++++++--
>> arch/arm/cpu/uncompress.c | 15 +++++++++++++++
>> 3 files changed, 42 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/arm/cpu/setupc_32.S b/arch/arm/cpu/setupc_32.S
>> index fa31f94442..fadfc28ae1 100644
>> --- a/arch/arm/cpu/setupc_32.S
>> +++ b/arch/arm/cpu/setupc_32.S
>> @@ -7,18 +7,30 @@
>> .section .text.setupc
>> /*
>> - * setup_c: clear bss
>> + * setup_c: clear bss if not yet done
>> */
>> ENTRY(setup_c)
>> push {r4, lr}
>> + ldr r0, =bss_cleared
>> + ldr r1, [r0]
>> + cmp r1, #0
>> + bne 1f /* skip if already done */
>> ldr r0, =__bss_start
>> mov r1, #0
>> ldr r2, =__bss_stop
>> sub r2, r2, r0
>> bl __memset /* clear bss */
>> - pop {r4, pc}
>> + ldr r0, =bss_cleared
>> + mov r1, #1
>> + str r1, [r0] /* mark bss cleared */
>> +1: pop {r4, pc}
>> ENDPROC(setup_c)
>> +.section .data.bss_cleared
>> +.balign 4
>> +bss_cleared:
>> + .word 0
>> +
>> /*
>> * void relocate_to_adr(unsigned long targetadr)
>> *
>> diff --git a/arch/arm/cpu/setupc_64.S b/arch/arm/cpu/setupc_64.S
>> index 18ab7ff3fe..a0767c5136 100644
>> --- a/arch/arm/cpu/setupc_64.S
>> +++ b/arch/arm/cpu/setupc_64.S
>> @@ -7,19 +7,30 @@
>> .section .text.setupc
>> /*
>> - * setup_c: clear bss
>> + * setup_c: clear bss if not yet done
>> */
>> ENTRY(setup_c)
>> + adr_l x0, bss_cleared
>> + ldr w1, [x0]
>> + cbnz w1, 1f /* skip if already done */
>> mov x15, x30
>> adr_l x0, __bss_start
>> mov x1, #0
>> adr_l x2, __bss_stop
>> sub x2, x2, x0
>> bl __memset /* clear bss */
>> + adr_l x0, bss_cleared
>> + mov w1, #1
>> + str w1, [x0] /* mark bss cleared */
>> mov x30, x15
>> - ret
>> +1: ret
>> ENDPROC(setup_c)
>> +.section .data.bss_cleared
>> +.balign 4
>> +bss_cleared:
>> + .word 0
>> +
>> /*
>> * void relocate_to_adr(unsigned long targetadr)
>> *
>> diff --git a/arch/arm/cpu/uncompress.c b/arch/arm/cpu/uncompress.c
>> index 38f7dbc113..bde0f2a0a5 100644
>> --- a/arch/arm/cpu/uncompress.c
>> +++ b/arch/arm/cpu/uncompress.c
>> @@ -50,6 +50,15 @@ void __noreturn barebox_pbl_start(unsigned long
>> membase, unsigned long memsize,
>> pg_start = runtime_address(input_data);
>> pg_end = runtime_address(input_data_end);
>> + puthex_ll((unsigned long)pg_start); putc_ll('\r'); putc_ll('\n');
>> + puthex_ll((unsigned long)pg_end); putc_ll('\r'); putc_ll('\n');
>> + puthex_ll((unsigned long)pc); putc_ll('\r'); putc_ll('\n');
>> + puthex_ll(membase); putc_ll('\r'); putc_ll('\n');
>> + puthex_ll(memsize); putc_ll('\r'); putc_ll('\n');
>> + puthex_ll((unsigned long)&__bss_start); putc_ll('\r');
>> putc_ll('\n');
>> + puthex_ll((unsigned long)&__bss_stop); putc_ll('\r'); putc_ll('\n');
>> + puthex_ll((unsigned long)&__image_end); putc_ll('\r');
>> putc_ll('\n');
>> +
>> /*
>> * If we run from inside the memory just relocate the binary
>> * to the current address. Otherwise it may be a readonly location.
>> @@ -60,11 +69,17 @@ void __noreturn barebox_pbl_start(unsigned long
>> membase, unsigned long memsize,
>> else
>> relocate_to_adr(membase);
>> + putc_ll('A');
>> +
>> pg_len = pg_end - pg_start;
>> uncompressed_len = get_unaligned((const u32 *)(pg_start + pg_len
>> - 4));
>> + putc_ll('B');
>> +
>> setup_c();
>> + putc_ll('C');
>> +
>> pr_debug("memory at 0x%08lx, size 0x%08lx\n", membase, memsize);
>> arm_pbl_init_exceptions();
>
>
>
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