diff options
| -rw-r--r-- | src/lib/imd_cbmem.c | 30 |
1 files changed, 18 insertions, 12 deletions
diff --git a/src/lib/imd_cbmem.c b/src/lib/imd_cbmem.c index 4fb78cef96..ba00c2e9db 100644 --- a/src/lib/imd_cbmem.c +++ b/src/lib/imd_cbmem.c @@ -24,24 +24,30 @@ #include <arch/early_variables.h> /* - * We need special handling on x86 before ramstage because we cannot use global - * variables (we're executing in-place from flash so we don't have a writable - * data segment, and we cannot use CAR_GLOBAL here since that mechanism itself - * is dependent on CBMEM). Therefore, we have to always try to partially recover - * CBMEM from cbmem_top() whenever we try to access it. In other environments - * we're not so constrained and just keep the backing imd struct in a global. - * This also means that we can easily tell whether CBMEM has explicitly been - * initialized or recovered yet on those platforms, and don't need to put the - * burden on board or chipset code to tell us by returning NULL from cbmem_top() - * before that point. + * We need special handling on x86 where CAR global migration is employed. One + * cannot use true globals in that circumstance because CAR is where the globals + * are backed -- creating a circular dependency. For non CAR platforms globals + * are free to be used as well as any stages that are purely executing out of + * RAM. For CAR platforms that don't migrate globals the as-linked globals can + * be used, but they need special decoration using CAR_GLOBAL. That ensures + * proper object placement in conjunction with the linker. + * + * For the CAR global migration platforms we have to always try to partially + * recover CBMEM from cbmem_top() whenever we try to access it. In other + * environments we're not so constrained and just keep the backing imd struct + * in a global. This also means that we can easily tell whether CBMEM has + * explicitly been initialized or recovered yet on those platforms, and don't + * need to put the burden on board or chipset code to tell us by returning + * NULL from cbmem_top() before that point. */ #define CAN_USE_GLOBALS \ - (!IS_ENABLED(CONFIG_ARCH_X86) || ENV_RAMSTAGE || ENV_POSTCAR) + (!IS_ENABLED(CONFIG_ARCH_X86) || ENV_RAMSTAGE || ENV_POSTCAR || \ + IS_ENABLED(CONFIG_NO_CAR_GLOBAL_MIGRATION)) static inline struct imd *cbmem_get_imd(void) { if (CAN_USE_GLOBALS) { - static struct imd imd_cbmem; + static struct imd imd_cbmem CAR_GLOBAL; return &imd_cbmem; } return NULL; |