[U-Boot] [RFC PATCH 2/2] x86: fsp: Move FspInitEntry call to board_init_f()

[Bin Meng]

The call to FspInitEntry is done in arch/x86/lib/fsp/fsp_car.S so far.
It worked pretty well but looks not that good. Apart from doing too
much work than just enabling CAR, it cannot read the configuration
data from device tree at that time. Now we want to move it a little
bit later as part of init_sequence_f[] being called by board_init_f().
This way it looks and works better in the U-Boot initialization path.

Due to FSP's design, after calling FspInitEntry it will not return to
its caller, instead it jumps to a continuation function which is given
by bootloader with a new stack in system memory. The original stack in
the CAR is gone, but its content is perserved by FSP and described by
a bootloader temporary memory HOB. Technically we can recover anything
we had before in the previous stack, but that is way too complicated.
To make life much easier, in the FSP continuation routine we just
simply call fsp_init_done() and jump back to car_init_ret() to redo
the whole board_init_f() initialization, but this time with a non-zero
HOB list pointer saved in U-Boot's global data so that we can bypass
the FspInitEntry for the second time.

Signed-off-by: Bin Meng <bmeng.cn at gmail.com>

---

 arch/x86/cpu/start.S              |  6 +++++-
 arch/x86/include/asm/u-boot-x86.h |  4 ++++
 arch/x86/lib/fsp/fsp_car.S        | 26 +++++---------------------
 arch/x86/lib/fsp/fsp_common.c     |  8 ++++++++
 common/board_f.c                  |  3 +++
 5 files changed, 25 insertions(+), 22 deletions(-)

diff --git a/arch/x86/cpu/start.S b/arch/x86/cpu/start.S
index 2e5f9da..00e585e 100644
--- a/arch/x86/cpu/start.S
+++ b/arch/x86/cpu/start.S
@@ -116,12 +116,16 @@ car_init_ret:
 	rep	stosb
 
 #ifdef CONFIG_HAVE_FSP
+	test	%esi, %esi
+	jz	skip_hob
+
 	/* Store HOB list */
 	movl	%esp, %edx
 	addl	$GD_HOB_LIST, %edx
 	movl	%esi, (%edx)
-#endif
 
+skip_hob:
+#endif
 	/* Setup first parameter to setup_gdt, pointer to global_data */
 	movl	%esp, %eax
 
diff --git a/arch/x86/include/asm/u-boot-x86.h b/arch/x86/include/asm/u-boot-x86.h
index faa5182..9ee4104 100644
--- a/arch/x86/include/asm/u-boot-x86.h
+++ b/arch/x86/include/asm/u-boot-x86.h
@@ -54,6 +54,10 @@ u32 isa_map_rom(u32 bus_addr, int size);
 /* arch/x86/lib/... */
 int video_bios_init(void);
 
+#ifdef CONFIG_HAVE_FSP
+int x86_fsp_init(void);
+#endif
+
 void	board_init_f_r_trampoline(ulong) __attribute__ ((noreturn));
 void	board_init_f_r(void) __attribute__ ((noreturn));
 
diff --git a/arch/x86/lib/fsp/fsp_car.S b/arch/x86/lib/fsp/fsp_car.S
index 5e09568..afbf3f9 100644
--- a/arch/x86/lib/fsp/fsp_car.S
+++ b/arch/x86/lib/fsp/fsp_car.S
@@ -56,28 +56,10 @@ temp_ram_init_ret:
 
 	/* stack grows down from top of CAR */
 	movl	%edx, %esp
+	subl	$4, %esp
 
-	/*
-	 * TODO:
-	 *
-	 * According to FSP architecture spec, the fsp_init() will not return
-	 * to its caller, instead it requires the bootloader to provide a
-	 * so-called continuation function to pass into the FSP as a parameter
-	 * of fsp_init, and fsp_init() will call that continuation function
-	 * directly.
-	 *
-	 * The call to fsp_init() may need to be moved out of the car_init()
-	 * to cpu_init_f() with the help of some inline assembly codes.
-	 * Note there is another issue that fsp_init() will setup another stack
-	 * using the fsp_init parameter stack_top after DRAM is initialized,
-	 * which means any data on the previous stack (on the CAR) gets lost
-	 * (ie: U-Boot global_data). FSP is supposed to support such scenario,
-	 * however it does not work. This should be revisited in the future.
-	 */
-	movl	$CONFIG_FSP_TEMP_RAM_ADDR, %eax
-	xorl	%edx, %edx
-	xorl	%ecx, %ecx
-	call	fsp_init
+	xor	%esi, %esi
+	jmp	car_init_done
 
 .global fsp_init_done
 fsp_init_done:
@@ -86,6 +68,8 @@ fsp_init_done:
 	 * Save eax to esi temporarily.
 	 */
 	movl	%eax, %esi
+
+car_init_done:
 	/*
 	 * Re-initialize the ebp (BIST) to zero, as we already reach here
 	 * which means we passed BIST testing before.
diff --git a/arch/x86/lib/fsp/fsp_common.c b/arch/x86/lib/fsp/fsp_common.c
index 001494d..5b25632 100644
--- a/arch/x86/lib/fsp/fsp_common.c
+++ b/arch/x86/lib/fsp/fsp_common.c
@@ -46,3 +46,11 @@ void board_final_cleanup(void)
 
 	return;
 }
+
+int x86_fsp_init(void)
+{
+	if (!gd->arch.hob_list)
+		fsp_init(CONFIG_FSP_TEMP_RAM_ADDR, BOOT_FULL_CONFIG, NULL);
+
+	return 0;
+}
diff --git a/common/board_f.c b/common/board_f.c
index fbbad1b..21be26f 100644
--- a/common/board_f.c
+++ b/common/board_f.c
@@ -753,6 +753,9 @@ static init_fnc_t init_sequence_f[] = {
 #ifdef CONFIG_OF_CONTROL
 	fdtdec_setup,
 #endif
+#if defined(CONFIG_X86) && defined(CONFIG_HAVE_FSP)
+	x86_fsp_init,
+#endif
 #ifdef CONFIG_TRACE
 	trace_early_init,
 #endif
-- 
1.8.2.1