arm: Correct comments in crt0.S for the recent SPL improvements
The current comments need a bit of tweaking since we now support stack
and global_data relocation in SPL. Also add a reference to the README.
For AArch64 this is not implemented, so leave a TODO for this.
Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Tim Harvey <tharvey@gateworks.com>
diff --git a/arch/arm/lib/crt0_64.S b/arch/arm/lib/crt0_64.S
index 98a906e..8b34e04 100644
--- a/arch/arm/lib/crt0_64.S
+++ b/arch/arm/lib/crt0_64.S
@@ -27,7 +27,8 @@
* the GD ('global data') structure, both located in some readily
* available RAM (SRAM, locked cache...). In this context, VARIABLE
* global data, initialized or not (BSS), are UNAVAILABLE; only
- * CONSTANT initialized data are available.
+ * CONSTANT initialized data are available. GD should be zeroed
+ * before board_init_f() is called.
*
* 2. Call board_init_f(). This function prepares the hardware for
* execution from system RAM (DRAM, DDR...) As system RAM may not
@@ -36,24 +37,31 @@
* data include the relocation destination, the future stack, and
* the future GD location.
*
- * (the following applies only to non-SPL builds)
- *
* 3. Set up intermediate environment where the stack and GD are the
* ones allocated by board_init_f() in system RAM, but BSS and
* initialized non-const data are still not available.
*
- * 4. Call relocate_code(). This function relocates U-Boot from its
- * current location into the relocation destination computed by
- * board_init_f().
+ * 4a.For U-Boot proper (not SPL), call relocate_code(). This function
+ * relocates U-Boot from its current location into the relocation
+ * destination computed by board_init_f().
+ *
+ * 4b.For SPL, board_init_f() just returns (to crt0). There is no
+ * code relocation in SPL.
*
* 5. Set up final environment for calling board_init_r(). This
* environment has BSS (initialized to 0), initialized non-const
* data (initialized to their intended value), and stack in system
- * RAM. GD has retained values set by board_init_f(). Some CPUs
- * have some work left to do at this point regarding memory, so
- * call c_runtime_cpu_setup.
+ * RAM (for SPL moving the stack and GD into RAM is optional - see
+ * CONFIG_SPL_STACK_R). GD has retained values set by board_init_f().
+ *
+ * TODO: For SPL, implement stack relocation on AArch64.
*
- * 6. Branch to board_init_r().
+ * 6. For U-Boot proper (not SPL), some CPUs have some work left to do
+ * at this point regarding memory, so call c_runtime_cpu_setup.
+ *
+ * 7. Branch to board_init_r().
+ *
+ * For more information see 'Board Initialisation Flow in README.
*/
ENTRY(_main)
@@ -106,6 +114,8 @@
*/
bl c_runtime_cpu_setup /* still call old routine */
+/* TODO: For SPL, call spl_relocate_stack_gd() to alloc stack relocation */
+
/*
* Clear BSS section
*/