From a5a5d997b41a1b63eed67e78fac1d015e3e070e2 Mon Sep 17 00:00:00 2001 From: Andreas Dannenberg Date: Tue, 4 Jun 2019 17:55:45 -0500 Subject: [PATCH] spl: Allow performing BSS init early before board_init_f() On some platform we have sufficient memory available early on to allow setting up and using a basic BSS prior to entering board_init_f(). Doing so can for example be used to carry state over to board_init_r() without having to resort to extending U-Boot's global data structure. To support such scenarios add a Kconfig option called CONFIG_SPL_EARLY_BSS to allow moving the initialization of BSS prior to entering board_init_f(), if enabled. Note that using this option usually should go along with using CONFIG_SPL_SEPARATE_BSS and configuring BSS to be located in memory actually available prior to board_init_f(). Signed-off-by: Andreas Dannenberg --- arch/arm/lib/crt0.S | 53 ++++++++++++++++++++++++++++++++++++----------------- common/spl/Kconfig | 10 ++++++++++ 2 files changed, 46 insertions(+), 17 deletions(-) diff --git a/arch/arm/lib/crt0.S b/arch/arm/lib/crt0.S index 30fba20..c74641d 100644 --- a/arch/arm/lib/crt0.S +++ b/arch/arm/lib/crt0.S @@ -58,6 +58,33 @@ */ /* + * Macro for clearing BSS during SPL execution. Usually called during the + * relocation process for most boards before entering board_init_r(), but + * can also be done early before entering board_init_f() on plaforms that + * can afford it due to sufficient memory being available early. + */ + +.macro SPL_CLEAR_BSS + ldr r0, =__bss_start /* this is auto-relocated! */ + +#ifdef CONFIG_USE_ARCH_MEMSET + ldr r3, =__bss_end /* this is auto-relocated! */ + mov r1, #0x00000000 /* prepare zero to clear BSS */ + + subs r2, r3, r0 /* r2 = memset len */ + bl memset +#else + ldr r1, =__bss_end /* this is auto-relocated! */ + mov r2, #0x00000000 /* prepare zero to clear BSS */ + +clbss_l:cmp r0, r1 /* while not at end of BSS */ + strlo r2, [r0] /* clear 32-bit BSS word */ + addlo r0, r0, #4 /* move to next */ + blo clbss_l +#endif +.endm + +/* * entry point of crt0 sequence */ @@ -82,6 +109,10 @@ ENTRY(_main) mov r9, r0 bl board_init_f_init_reserve +#if defined(CONFIG_SPL_EARLY_BSS) + SPL_CLEAR_BSS +#endif + mov r0, #0 bl board_init_f @@ -119,6 +150,11 @@ here: bl c_runtime_cpu_setup /* we still call old routine here */ #endif #if !defined(CONFIG_SPL_BUILD) || defined(CONFIG_SPL_FRAMEWORK) + +#if !defined(CONFIG_SPL_EARLY_BSS) + SPL_CLEAR_BSS +#endif + # ifdef CONFIG_SPL_BUILD /* Use a DRAM stack for the rest of SPL, if requested */ bl spl_relocate_stack_gd @@ -126,23 +162,6 @@ here: movne sp, r0 movne r9, r0 # endif - ldr r0, =__bss_start /* this is auto-relocated! */ - -#ifdef CONFIG_USE_ARCH_MEMSET - ldr r3, =__bss_end /* this is auto-relocated! */ - mov r1, #0x00000000 /* prepare zero to clear BSS */ - - subs r2, r3, r0 /* r2 = memset len */ - bl memset -#else - ldr r1, =__bss_end /* this is auto-relocated! */ - mov r2, #0x00000000 /* prepare zero to clear BSS */ - -clbss_l:cmp r0, r1 /* while not at end of BSS */ - strlo r2, [r0] /* clear 32-bit BSS word */ - addlo r0, r0, #4 /* move to next */ - blo clbss_l -#endif #if ! defined(CONFIG_SPL_BUILD) bl coloured_LED_init diff --git a/common/spl/Kconfig b/common/spl/Kconfig index 7122c06..5978fb2 100644 --- a/common/spl/Kconfig +++ b/common/spl/Kconfig @@ -248,6 +248,16 @@ config TPL_BANNER_PRINT info. Disabling this option could be useful to reduce SPL boot time (e.g. approx. 6 ms faster, when output on i.MX6 with 115200 baud). +config SPL_EARLY_BSS + depends on ARM && !ARM64 + bool "Allows initializing BSS early before entering board_init_f" + help + On some platform we have sufficient memory available early on to + allow setting up and using a basic BSS prior to entering + board_init_f. Activating this option will also de-activate the + clearing of BSS during the SPL relocation process, thus allowing + to carry state from board_init_f to board_init_r by way of BSS. + config SPL_DISPLAY_PRINT bool "Display a board-specific message in SPL" help -- 2.7.4