armv8: spl: Call board_init_r from crt0_64 in SPL

As part of the startup process for boards using the SPL, the
meaning of board_init_f changed such that it should return normally
rather than calling board_init_r directly. (see
db910353a126d84fe8dff7a694ea792f50fcfb6a )
This was fixed in 32-bit arm, but broke when SPL was added to
64 bit arm. This fixes crt0_64 so that it calls board_init_r
during the SPL and removes the direct call from board_init_f
from the arm SPL example.

Signed-off-by: Jeremy Hunt <Jeremy.Hunt@DEShawResearch.com>

Acked-by: Simon Glass <sjg@chromium.org>

arch/arm/lib/crt0_64.S

@@ -108,6 +108,7 @@ relocation_return:
  * Set up final (full) environment
  */
 	bl	c_runtime_cpu_setup		/* still call old routine */
+#endif /* !CONFIG_SPL_BUILD */
 
 /* TODO: For SPL, call spl_relocate_stack_gd() to alloc stack relocation */
 
@@ -130,6 +131,4 @@ clear_loop:
 
 	/* NOTREACHED - board_init_r() does not return */
 
-#endif /* !CONFIG_SPL_BUILD */
-
 ENDPROC(_main)

arch/arm/lib/spl.c

@@ -25,22 +25,20 @@ gd_t gdata __attribute__ ((section(".data")));
 #endif
 
 /*
- * In the context of SPL, board_init_f must ensure that any clocks/etc for
- * DDR are enabled, ensure that the stack pointer is valid, clear the BSS
- * and call board_init_r.  We provide this version by default but mark it
- * as __weak to allow for platforms to do this in their own way if needed.
+ * In the context of SPL, board_init_f() prepares the hardware for execution
+ * from system RAM (DRAM, DDR...). As system RAM may not be available yet,
+ * board_init_f() must use the current GD to store any data which must be
+ * passed on to later stages. These data include the relocation destination,
+ * the future stack, and the future GD location. BSS is cleared after this
+ * function (and therefore must be accessible).
+ *
+ * We provide this version by default but mark it as __weak to allow for
+ * platforms to do this in their own way if needed. Please see the top
+ * level U-Boot README "Board Initialization Flow" section for info on what
+ * to put in this function.
  */
 void __weak board_init_f(ulong dummy)
 {
-	/* Clear the BSS. */
-	memset(__bss_start, 0, __bss_end - __bss_start);
-
-#ifndef CONFIG_SPL_DM
-	/* TODO: Remove settings of the global data pointer here */
-	gd = &gdata;
-#endif
-
-	board_init_r(NULL, 0);
 }
 
 /*