MIPS: make inclusion of ROM exception vectors configurable

This adds a compile time option to include code for static
exception vectors. Static exception vectors are only needed,
when the U-Boot entry point is equal to the CPU reset exception
vector address. For instance this is the case when U-Boot is
used as ROM in Qemu or booted from parallel NOR flash. When
U-Boot is booted from RAM (e.g. loaded there by SPL), the
exception vectors need to be setup dynamically, which is done
in follow-up commits.

Signed-off-by: Daniel Schwierzeck <daniel.schwierzeck@gmail.com>

arch/mips/Kconfig

@@ -20,6 +20,7 @@ config TARGET_QEMU_MIPS
 	select SUPPORTS_CPU_MIPS32_R2
 	select SUPPORTS_CPU_MIPS64_R1
 	select SUPPORTS_CPU_MIPS64_R2
+	select ROM_EXCEPTION_VECTORS
 
 config TARGET_MALTA
 	bool "Support malta"
@@ -40,6 +41,7 @@ config TARGET_MALTA
 	select SUPPORTS_CPU_MIPS64_R6
 	select SWAP_IO_SPACE
 	select MIPS_L1_CACHE_SHIFT_6
+	select ROM_EXCEPTION_VECTORS
 
 config TARGET_VCT
 	bool "Support vct"
@@ -47,6 +49,7 @@ config TARGET_VCT
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select SYS_MIPS_CACHE_INIT_RAM_LOAD
+	select ROM_EXCEPTION_VECTORS
 
 config TARGET_DBAU1X00
 	bool "Support dbau1x00"
@@ -55,6 +58,7 @@ config TARGET_DBAU1X00
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select SYS_MIPS_CACHE_INIT_RAM_LOAD
+	select ROM_EXCEPTION_VECTORS
 	select MIPS_TUNE_4KC
 
 config TARGET_PB1X00
@@ -63,6 +67,7 @@ config TARGET_PB1X00
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select SYS_MIPS_CACHE_INIT_RAM_LOAD
+	select ROM_EXCEPTION_VECTORS
 	select MIPS_TUNE_4KC
 
 config ARCH_ATH79
@@ -91,6 +96,7 @@ config TARGET_BOSTON
 	select SUPPORTS_CPU_MIPS64_R1
 	select SUPPORTS_CPU_MIPS64_R2
 	select SUPPORTS_CPU_MIPS64_R6
+	select ROM_EXCEPTION_VECTORS
 
 config TARGET_XILFPGA
 	bool "Support Imagination Xilfpga"
@@ -103,6 +109,7 @@ config TARGET_XILFPGA
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
 	select MIPS_L1_CACHE_SHIFT_4
+	select ROM_EXCEPTION_VECTORS
 	help
 	  This supports IMGTEC MIPSfpga platform
 
@@ -192,6 +199,20 @@ config CPU_MIPS64_R6
 
 endchoice
 
+menu "General setup"
+
+config ROM_EXCEPTION_VECTORS
+	bool "Build U-Boot image with exception vectors"
+	help
+	  Enable this to include exception vectors in the U-Boot image. This is
+	  required if the U-Boot entry point is equal to the address of the
+	  CPU reset exception vector (e.g. U-Boot as ROM loader in Qemu,
+	  U-Boot booted from parallel NOR flash).
+	  Disable this, if the U-Boot image is booted from DRAM (e.g. by SPL).
+	  In that case the image size will be reduced by 0x500 bytes.
+
+endmenu
+
 menu "OS boot interface"
 
 config MIPS_BOOT_CMDLINE_LEGACY

arch/mips/cpu/start.S

@@ -57,7 +57,6 @@ ENTRY(_start)
 	b	reset
 	 nop
 
-	.org 0x10
 #if defined(CONFIG_SYS_XWAY_EBU_BOOTCFG)
 	/*
 	 * Almost all Lantiq XWAY SoC devices have an external bus unit (EBU) to
@@ -66,16 +65,20 @@ ENTRY(_start)
 	 * initial configuration for that EBU in order to access the flash
 	 * device with correct parameters. This config option is board-specific.
 	 */
+	.org 0x10
 	.word CONFIG_SYS_XWAY_EBU_BOOTCFG
 	.word 0x0
-#elif defined(CONFIG_MALTA)
+#endif
+#if defined(CONFIG_MALTA)
 	/*
 	 * Linux expects the Board ID here.
 	 */
+	.org 0x10
 	.word 0x00000420	# 0x420 (Malta Board with CoreLV)
 	.word 0x00000000
 #endif
 
+#if defined(CONFIG_ROM_EXCEPTION_VECTORS)
 	.org 0x200
 	/* TLB refill, 32 bit task */
 1:	b	1b
@@ -106,7 +109,9 @@ ENTRY(_start)
 1:	b	1b
 	 nop
 
-	.align 4
+	.org 0x500
+#endif
+
 reset:
 #if __mips_isa_rev >= 6
 	mfc0	t0, CP0_CONFIG, 5

arch/mips/mach-ath79/Kconfig

@@ -9,6 +9,7 @@ config SOC_AR933X
 	select SUPPORTS_BIG_ENDIAN
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
+	select ROM_EXCEPTION_VECTORS
 	select MIPS_TUNE_24KC
 	help
 	  This supports QCA/Atheros ar933x family SOCs.
@@ -27,6 +28,7 @@ config SOC_QCA953X
 	select SUPPORTS_BIG_ENDIAN
 	select SUPPORTS_CPU_MIPS32_R1
 	select SUPPORTS_CPU_MIPS32_R2
+	select ROM_EXCEPTION_VECTORS
 	select MIPS_TUNE_24KC
 	help
 	  This supports QCA/Atheros qca953x family SOCs.

arch/mips/mach-pic32/Kconfig

@@ -14,6 +14,7 @@ config SOC_PIC32MZDA
 	select SUPPORTS_CPU_MIPS32_R2
 	select MIPS_L1_CACHE_SHIFT_4
 	select SYS_MIPS_CACHE_INIT_RAM_LOAD
+	select ROM_EXCEPTION_VECTORS
 	help
 	  This supports Microchip PIC32MZ[DA] family of microcontrollers.