[U-Boot] [PATCH 5/5] RFC: sunxi: WIP FEL support

[Simon Glass <sjg@chromium.org>]

(What does FEL stand for?)

This is an attempt to make sunxi's FEL code fit with the normal U-Boot
boot sequence instead of creating its own.

Most of the FEL special-case code is removed, although I may have gone too
far with my changes to generate a u-boot-sunxi-with-spl.bin file even when
FEL is enabled. This may not be possible since the MMC stack makes SPL
too large for FEL anyway, although it may be possible for other boot
mediums.

This series is available at u-boot-dm, branch sunxi-working.

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

 arch/arm/cpu/armv7/sunxi/Makefile           |  4 +-
 arch/arm/cpu/armv7/sunxi/board.c            | 21 ++++++++
 arch/arm/cpu/armv7/sunxi/config.mk          |  2 -
 arch/arm/cpu/armv7/sunxi/fel_utils.S        | 26 +++++++++
 arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds | 82 -----------------------------
 arch/arm/include/asm/arch-sunxi/sys_proto.h | 10 ++++
 board/sunxi/Kconfig                         | 10 ++++
 include/configs/sunxi-common.h              |  6 +--
 scripts/Makefile.spl                        |  2 -
 9 files changed, 70 insertions(+), 93 deletions(-)
 create mode 100644 arch/arm/cpu/armv7/sunxi/fel_utils.S
 delete mode 100644 arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds

diff --git a/arch/arm/cpu/armv7/sunxi/Makefile b/arch/arm/cpu/armv7/sunxi/Makefile
index 48db744..c1b975a 100644
--- a/arch/arm/cpu/armv7/sunxi/Makefile
+++ b/arch/arm/cpu/armv7/sunxi/Makefile
@@ -38,7 +38,5 @@ obj-$(CONFIG_MACH_SUN5I)	+= dram_sun4i.o
 obj-$(CONFIG_MACH_SUN6I)	+= dram_sun6i.o
 obj-$(CONFIG_MACH_SUN7I)	+= dram_sun4i.o
 obj-$(CONFIG_MACH_SUN8I)	+= dram_sun8i.o
-ifdef CONFIG_SPL_FEL
-obj-y	+= start.o
-endif
+obj-y	+= fel_utils.o
 endif
diff --git a/arch/arm/cpu/armv7/sunxi/board.c b/arch/arm/cpu/armv7/sunxi/board.c
index 6e28bcd..b7492ac 100644
--- a/arch/arm/cpu/armv7/sunxi/board.c
+++ b/arch/arm/cpu/armv7/sunxi/board.c
@@ -27,6 +27,13 @@
 
 #include <linux/compiler.h>
 
+struct fel_stash {
+	uint32_t sp;
+	uint32_t lr;
+};
+
+struct fel_stash fel_stash __attribute__((section(".data")));
+
 static int gpio_init(void)
 {
 #if CONFIG_CONS_INDEX == 1 && defined(CONFIG_UART0_PORT_F)
@@ -65,6 +72,12 @@ static int gpio_init(void)
 	return 0;
 }
 
+void spl_board_load_image(void)
+{
+	debug("Returning to FEL sp=%x, lr=%x\n", fel_stash.sp, fel_stash.lr);
+	return_to_fel(fel_stash.sp, fel_stash.lr);
+}
+
 void s_init(void)
 {
 #if defined CONFIG_MACH_SUN6I || defined CONFIG_MACH_SUN8I
@@ -95,6 +108,14 @@ void s_init(void)
  */
 u32 spl_boot_device(void)
 {
+	/*
+	 * Have we been asked to return to the FEL portion of the boot ROM?
+	 * TODO: We need a more robust test here, or bracket this with
+	 * #ifdef CONFIG_SPL_FEL.
+	 */
+	if (fel_stash.lr >= 0xffff0000 && fel_stash.lr < 0xffff4000)
+		return BOOT_DEVICE_BOARD;
+
 	return BOOT_DEVICE_MMC1;
 }
 
diff --git a/arch/arm/cpu/armv7/sunxi/config.mk b/arch/arm/cpu/armv7/sunxi/config.mk
index 00f5ffc..76ffec9 100644
--- a/arch/arm/cpu/armv7/sunxi/config.mk
+++ b/arch/arm/cpu/armv7/sunxi/config.mk
@@ -1,8 +1,6 @@
 # Build a combined spl + u-boot image
 ifdef CONFIG_SPL
 ifndef CONFIG_SPL_BUILD
-ifndef CONFIG_SPL_FEL
 ALL-y += u-boot-sunxi-with-spl.bin
 endif
 endif
-endif
diff --git a/arch/arm/cpu/armv7/sunxi/fel_utils.S b/arch/arm/cpu/armv7/sunxi/fel_utils.S
new file mode 100644
index 0000000..42739df
--- /dev/null
+++ b/arch/arm/cpu/armv7/sunxi/fel_utils.S
@@ -0,0 +1,26 @@
+/*
+ * Utility functions for FEL mode.
+ *
+ * Copyright (c) 2015 Google, Inc
+ *
+ * SPDX-License-Identifier:	GPL-2.0+
+ */
+
+#include <asm-offsets.h>
+#include <config.h>
+#include <asm/system.h>
+#include <linux/linkage.h>
+
+ENTRY(save_boot_params)
+	ldr	r0, =fel_stash
+	str	sp, [r0, #0]
+	str	r4, [r0, #4]	/* Store lr */
+	mov	r0, #RESET_SKIP_VBVAR | RESET_SKIP_CP15
+	bx	lr
+ENDPROC(save_boot_params)
+
+ENTRY(return_to_fel)
+	mov	sp, r0
+	mov	lr, r1
+	bx	lr
+ENDPROC(return_to_fel)
diff --git a/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds b/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds
deleted file mode 100644
index 928b7c1..0000000
--- a/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds
+++ /dev/null
@@ -1,82 +0,0 @@
-/*
- * (C) Copyright 2013
- * Henrik Nordstrom <henrik@henriknordstrom.net>
- *
- * SPDX-License-Identifier:	GPL-2.0+
- */
-OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
-OUTPUT_ARCH(arm)
-ENTRY(s_init)
-SECTIONS
-{
-	. = 0x00002000;
-
-	. = ALIGN(4);
-	.text :
-	{
-		*(.text.s_init)
-		*(.text*)
-	}
-
-	. = ALIGN(4);
-	.rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) }
-
-	. = ALIGN(4);
-	.data : {
-		*(.data*)
-	}
-
-	. = ALIGN(4);
-	.u_boot_list : {
-		KEEP(*(SORT(.u_boot_list*)));
-	}
-
-	. = ALIGN(4);
-	. = .;
-
-	. = ALIGN(4);
-	.rel.dyn : {
-		__rel_dyn_start = .;
-		*(.rel*)
-		__rel_dyn_end = .;
-	}
-
-	.dynsym : {
-		__dynsym_start = .;
-		*(.dynsym)
-	}
-
-	. = ALIGN(4);
-	.note.gnu.build-id :
-	{
-		*(.note.gnu.build-id)
-	}
-	_end = .;
-
-	. = ALIGN(4096);
-	.mmutable : {
-		*(.mmutable)
-	}
-
-	.bss_start __rel_dyn_start (OVERLAY) : {
-		KEEP(*(.__bss_start));
-		__bss_base = .;
-	}
-
-	.bss __bss_base (OVERLAY) : {
-		*(.bss*)
-		. = ALIGN(4);
-		__bss_limit = .;
-	}
-
-	.bss_end __bss_limit (OVERLAY) : {
-		KEEP(*(.__bss_end));
-	}
-
-	/DISCARD/ : { *(.dynstr*) }
-	/DISCARD/ : { *(.dynamic*) }
-	/DISCARD/ : { *(.plt*) }
-	/DISCARD/ : { *(.interp*) }
-	/DISCARD/ : { *(.gnu*) }
-	/DISCARD/ : { *(.note*) }
-}
diff --git a/arch/arm/include/asm/arch-sunxi/sys_proto.h b/arch/arm/include/asm/arch-sunxi/sys_proto.h
index c3e636e..60a5bd8 100644
--- a/arch/arm/include/asm/arch-sunxi/sys_proto.h
+++ b/arch/arm/include/asm/arch-sunxi/sys_proto.h
@@ -13,4 +13,14 @@
 
 void sdelay(unsigned long);
 
+/* return_to_fel() - Return to BROM from SPL
+ *
+ * This returns back into the BROM after U-Boot SPL has performed its initial
+ * init. It uses the provided lr and sp to do so.
+ *
+ * @lr:		BROM link register value (return address)
+ * @sp:		BROM stack pointer
+ */
+void return_to_fel(uint32_t lr, uint32_t sp);
+
 #endif
diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
index 4a21589..c50cffe 100644
--- a/board/sunxi/Kconfig
+++ b/board/sunxi/Kconfig
@@ -149,6 +149,16 @@ config SPL_FEL
 	bool "SPL/FEL mode support"
 	depends on SPL
 	default n
+	help
+	  This enables support for <insert_full_name_here> (FEL) mode. This
+	  allows U-Boot to be loaded to the board over USB by the on-chip
+	  boot rom. U-Boot should be sent in two parts: SPL first, with
+	  'fel write 0x2000 u-boot-spl.bin; fel exe 0x2000' then U-Boot with
+	  'fel write 0x4a000000 u-boot.bin; fel exe 0x4a000000'. This option
+	  shrinks the amount of SRAM available to SPL, so only enable it if
+	  you need FEL (why? what do we lose?). Note that enabling this option
+	  only allows FEL to be used; it is still possible to boot U-Boot from
+	  boot media. U-Boot SPL detects when it is being loaded using FEL.
 
 config UART0_PORT_F
 	bool "UART0 on MicroSD breakout board"
diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h
index 6cfd7e1..3becb4f 100644
--- a/include/configs/sunxi-common.h
+++ b/include/configs/sunxi-common.h
@@ -18,10 +18,8 @@
  */
 #define CONFIG_SUNXI		/* sunxi family */
 #ifdef CONFIG_SPL_BUILD
-#ifndef CONFIG_SPL_FEL
 #define CONFIG_SYS_THUMB_BUILD	/* Thumbs mode to save space in SPL */
 #endif
-#endif
 
 #include <asm/arch/cpu.h>	/* get chip and board defs */
 
@@ -146,10 +144,10 @@
 #define CONFIG_SPL_SERIAL_SUPPORT
 #define CONFIG_SPL_LIBGENERIC_SUPPORT
 
+#define CONFIG_SPL_BOARD_LOAD_IMAGE
+
 #ifdef CONFIG_SPL_FEL
 
-#define CONFIG_SPL_LDSCRIPT "arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds"
-#define CONFIG_SPL_START_S_PATH "arch/arm/cpu/armv7/sunxi"
 #define CONFIG_SPL_TEXT_BASE		0x2000
 #define CONFIG_SPL_MAX_SIZE		0x4000		/* 16 KiB */
 
diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
index ecf3037..5a1962b 100644
--- a/scripts/Makefile.spl
+++ b/scripts/Makefile.spl
@@ -153,10 +153,8 @@ ALL-y	+= $(obj)/$(BOARD)-spl.bin
 endif
 
 ifdef CONFIG_SUNXI
-ifndef CONFIG_SPL_FEL
 ALL-y	+= $(obj)/sunxi-spl.bin
 endif
-endif
 
 ifeq ($(CONFIG_SYS_SOC),"at91")
 ALL-y	+= boot.bin
-- 
2.2.0.rc0.207.ga3a616c