]>
Commit | Line | Data |
---|---|---|
6a11cf48 DS |
1 | Generic SPL framework |
2 | ===================== | |
3 | ||
4 | Overview | |
5 | -------- | |
6 | ||
7 | To unify all existing implementations for a secondary program loader (SPL) | |
8 | and to allow simply adding of new implementations this generic SPL framework | |
9 | has been created. With this framework almost all source files for a board | |
10 | can be reused. No code duplication or symlinking is necessary anymore. | |
11 | ||
12 | ||
13 | How it works | |
14 | ------------ | |
15 | ||
4379ac61 | 16 | There is a new directory $(srctree)/spl which contains only a Makefile. |
6a11cf48 DS |
17 | The object files are built separately for SPL and placed in this directory. |
18 | The final binaries which are generated are u-boot-spl, u-boot-spl.bin and | |
19 | u-boot-spl.map. | |
20 | ||
21 | During the SPL build a variable named CONFIG_SPL_BUILD is exported | |
22 | in the make environment and also appended to CPPFLAGS with -DCONFIG_SPL_BUILD. | |
23 | Source files can therefore be compiled for SPL with different settings. | |
24 | ARM-based boards have previously used the option CONFIG_PRELOADER for it. | |
25 | ||
26 | For example: | |
27 | ||
28 | ifeq ($(CONFIG_SPL_BUILD),y) | |
29 | COBJS-y += board_spl.o | |
30 | else | |
31 | COBJS-y += board.o | |
32 | endif | |
33 | ||
34 | COBJS-$(CONFIG_SPL_BUILD) += foo.o | |
35 | ||
36 | #ifdef CONFIG_SPL_BUILD | |
04e5ae79 | 37 | foo(); |
6a11cf48 DS |
38 | #endif |
39 | ||
40 | ||
41 | The building of SPL images can be with: | |
42 | ||
43 | #define CONFIG_SPL | |
44 | ||
fd3d28e7 PM |
45 | Because SPL images normally have a different text base, one has to be |
46 | configured by defining CONFIG_SPL_TEXT_BASE. The linker script has to be | |
6a11cf48 DS |
47 | defined with CONFIG_SPL_LDSCRIPT. |
48 | ||
49 | To support generic U-Boot libraries and drivers in the SPL binary one can | |
50 | optionally define CONFIG_SPL_XXX_SUPPORT. Currently following options | |
51 | are supported: | |
52 | ||
53 | CONFIG_SPL_LIBCOMMON_SUPPORT (common/libcommon.o) | |
54 | CONFIG_SPL_LIBDISK_SUPPORT (disk/libdisk.o) | |
55 | CONFIG_SPL_I2C_SUPPORT (drivers/i2c/libi2c.o) | |
56 | CONFIG_SPL_GPIO_SUPPORT (drivers/gpio/libgpio.o) | |
57 | CONFIG_SPL_MMC_SUPPORT (drivers/mmc/libmmc.o) | |
58 | CONFIG_SPL_SERIAL_SUPPORT (drivers/serial/libserial.o) | |
59 | CONFIG_SPL_SPI_FLASH_SUPPORT (drivers/mtd/spi/libspi_flash.o) | |
60 | CONFIG_SPL_SPI_SUPPORT (drivers/spi/libspi.o) | |
61 | CONFIG_SPL_FAT_SUPPORT (fs/fat/libfat.o) | |
62 | CONFIG_SPL_LIBGENERIC_SUPPORT (lib/libgeneric.o) | |
682b3a81 | 63 | CONFIG_SPL_POWER_SUPPORT (drivers/power/libpower.o) |
12c2f1ee | 64 | CONFIG_SPL_NAND_SUPPORT (drivers/mtd/nand/libnand.o) |
6609916e | 65 | CONFIG_SPL_DRIVERS_MISC_SUPPORT (drivers/misc) |
3a0d60c5 | 66 | CONFIG_SPL_DMA_SUPPORT (drivers/dma/libdma.o) |
18e8ff18 | 67 | CONFIG_SPL_POST_MEM_SUPPORT (post/drivers/memory.o) |
435199f3 | 68 | CONFIG_SPL_NAND_LOAD (drivers/mtd/nand/nand_spl_load.o) |
32b11273 | 69 | CONFIG_SPL_SPI_LOAD (drivers/mtd/spi/spi_spl_load.o) |
c57b953d | 70 | CONFIG_SPL_RAM_DEVICE (common/spl/spl.c) |
a09f9649 | 71 | CONFIG_SPL_WATCHDOG_SUPPORT (drivers/watchdog/libwatchdog.o) |
d22650af AM |
72 | |
73 | Normally CPU is assumed to be the same between the SPL and normal | |
74 | u-boot build. However it is possible to specify a different CPU for | |
75 | the SPL build for cases where the SPL is expected to run on a | |
76 | different CPU model from the main u-boot. This is done by specifying | |
77 | an SPL CPU in boards.cfg as follows: | |
78 | ||
79 | normal_cpu:spl_cpu | |
80 | ||
a544eadd | 81 | This case CPU will be set to "normal_cpu" during the main u-boot |
d22650af | 82 | build and "spl_cpu" during the SPL build. |
f8e754d5 TR |
83 | |
84 | ||
85 | Debugging | |
86 | --------- | |
87 | ||
88 | When building SPL with DEBUG set you may also need to set CONFIG_PANIC_HANG | |
89 | as in most cases do_reset is not defined within SPL. | |
c3567d80 TR |
90 | |
91 | ||
92 | Estimating stack usage | |
93 | ---------------------- | |
94 | ||
95 | With gcc 4.6 (and later) and the use of GNU cflow it is possible to estimate | |
96 | stack usage at various points in run sequence of SPL. The -fstack-usage option | |
97 | to gcc will produce '.su' files (such as arch/arm/cpu/armv7/syslib.su) that | |
98 | will give stack usage information and cflow can construct program flow. | |
99 | ||
100 | Must have gcc 4.6 or later, which supports -fstack-usage | |
101 | ||
102 | 1) Build normally | |
103 | 2) Perform the following shell command to generate a list of C files used in | |
104 | SPL: | |
105 | $ find spl -name '*.su' | sed -e 's:^spl/::' -e 's:[.]su$:.c:' > used-spl.list | |
106 | 3) Execute cflow: | |
107 | $ cflow --main=board_init_r `cat used-spl.list` 2>&1 | $PAGER | |
108 | ||
109 | cflow will spit out a number of warnings as it does not parse | |
110 | the config files and picks functions based on #ifdef. Parsing the '.i' | |
111 | files instead introduces another set of headaches. These warnings are | |
112 | not usually important to understanding the flow, however. |