Add a new config option to allow u-boot to reuse the FDT provided by the previous stage bootloader when available.

On some boards the previous stage bootloader can populate platform-specific parts of the devicetree such as the memory node, this allows us to avoid hardcoding it in u-boot and instead determine it dynamically at runtime.

Signed-off-by: Caleb Connolly caleb.connolly@linaro.org --- This patch will improve generic support for Qualcomm boards by enabling us to configure the memory map at runtime rather than having hardcoded maps on a per-device basis. I've gone for this approach initially to try and avoid introducing board specific code where possible, but I'm happy to rework this into mach-snapdragon if that's preferred. --- Changes in v2: - Replace pre-processor conditional with runtime IS_ENABLED() - Link to v1: https://lore.kernel.org/r/20231024-b4-prevbl-fdt-v1-1-541f71dba802@linaro.or... --- base-commit: e65b5d35c9116485366bb08138043d51220551da

// Caleb (they/them) --- arch/arm/lib/save_prev_bl_data.c | 7 +++++++ boot/Kconfig | 10 ++++++++++ include/init.h | 11 +++++++++++ lib/fdtdec.c | 8 +++++++- 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/arch/arm/lib/save_prev_bl_data.c b/arch/arm/lib/save_prev_bl_data.c index f7b23faf0d66..b0608502535e 100644 --- a/arch/arm/lib/save_prev_bl_data.c +++ b/arch/arm/lib/save_prev_bl_data.c @@ -45,6 +45,13 @@ bool is_addr_accessible(phys_addr_t addr) return false; }

+phys_addr_t get_prev_bl_fdt_addr(void) +{ + if (!is_addr_accessible((phys_addr_t)reg0)) + return 0; + return reg0; +} + int save_prev_bl_data(void) { struct fdt_header *fdt_blob; diff --git a/boot/Kconfig b/boot/Kconfig index a01e6cb8aafe..c127ba254589 100644 --- a/boot/Kconfig +++ b/boot/Kconfig @@ -1599,6 +1599,16 @@ config SAVE_PREV_BL_INITRAMFS_START_ADDR If no initramfs was provided by previous bootloader, no env variables will be created.

+config USE_PREV_BL_FDT + depends on SAVE_PREV_BL_FDT_ADDR && !OF_BOARD + bool "Use the FDT provided by the previous stage bootloader" + help + When u-boot is chain-loaded from a previous bootloader, enable this option + to use the FDT provided by the previous bootloader instead of any built-in + to u-boot. + + If no FDT was available, u-boot will fall back to its internal FDT. + menu "Configuration editor"

config CEDIT diff --git a/include/init.h b/include/init.h index 4e7fe26c2004..ca78ff9f08c4 100644 --- a/include/init.h +++ b/include/init.h @@ -168,6 +168,17 @@ defined(CONFIG_SAVE_PREV_BL_FDT_ADDR) * Return: 0 if ok; -ENODATA on error */ int save_prev_bl_data(void); + +/** + * get_prev_bl_fdt_addr - When u-boot is chainloaded, get the address + * of the FDT passed by the previous bootloader. + * + * Return: the address of the FDT passed by the previous bootloader + * or 0 if not found. + */ +phys_addr_t get_prev_bl_fdt_addr(void); +#else +#define get_prev_bl_fdt_addr() 0LLU #endif

/** diff --git a/lib/fdtdec.c b/lib/fdtdec.c index 7a6916764835..b82baf08fc2f 100644 --- a/lib/fdtdec.c +++ b/lib/fdtdec.c @@ -1222,7 +1222,7 @@ static int uncompress_blob(const void *src, ulong sz_src, void **dstp) */ static void *fdt_find_separate(void) { - void *fdt_blob = NULL; + void *fdt_blob = NULL, *prevbl_fdt_blob;

if (IS_ENABLED(CONFIG_SANDBOX)) return NULL; @@ -1234,6 +1234,12 @@ static void *fdt_find_separate(void) else fdt_blob = (ulong *)__bss_end; #else + if (IS_ENABLED(CONFIG_USE_PREV_BL_FDT)) { + prevbl_fdt_blob = (void *)get_prev_bl_fdt_addr(); + if (prevbl_fdt_blob) + return prevbl_fdt_blob; + } + /* FDT is at end of image */ fdt_blob = (ulong *)_end;