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author | Sean Anderson <sean.anderson@seco.com> | 2022-03-22 16:59:19 -0400 |
---|---|---|
committer | Tom Rini <trini@konsulko.com> | 2022-04-01 15:03:13 -0400 |
commit | 8e1c9fe243a31a0b0a40a80cc20fc3c06246d675 (patch) | |
tree | 5b76008074fe6615f96c318e9fe656c65e4c65e5 | |
parent | 12a05b3bcd85ff4aa930e7a1fb8795d5a6bfdf81 (diff) | |
download | u-boot-8e1c9fe243a31a0b0a40a80cc20fc3c06246d675.zip u-boot-8e1c9fe243a31a0b0a40a80cc20fc3c06246d675.tar.gz u-boot-8e1c9fe243a31a0b0a40a80cc20fc3c06246d675.tar.bz2 |
spl: Add semihosting boot method
This adds a boot method for loading the next stage from the host. It is
mostly modeled off of spl_load_image_ext. I am not really sure why/how
spl_load_image_fat uses three different methods to load the image, but
the simple case seems to work OK for now.
To control the presence of this boot method, we add a config symbol.
While we're at it, we update the original semihosting config symbol.
I think semihosting has some advantages of other forms of JTAG boot.
Common other ways to boot from JTAG include:
- Implementing DDR initialization through JTAG (typically with dozens of
lines of TCL) and then loading U-Boot. The DDR initialization
typically uses hard-coded register writes, and is not easily adapted
to different boards. BOOT_DEVICE_SMH allows booting with SPL,
leveraging U-Boot's existing DDR initialization code. This is the
method used by NXP's CodeWarrior IDE on Layerscape processors (see
AN12270).
- Loading a bootloader into SDRAM, waiting for it to initialize DDR, and
then loading U-Boot. This is tricky, because the debugger must stop the
boot after the bootloader has completed its work. Trying to load
U-Boot too early can cause failure to boot. This is the method used by
Xilinx with its Zynq(MP) processors.
- Loading SPL with BOOT_DEVICE_RAM and breaking before SPL loads the
image to load U-Boot at the appropriate place. This can be a bit
tricky, because the load address is dependent on the header size. An
elf with symbols must also be used in order to stop at the appropriate
point. BOOT_DEVICE_SMH can be viewed as an extension of this process,
where SPL automatically stops and tells the host where to place the
image.
Signed-off-by: Sean Anderson <sean.anderson@seco.com>
-rw-r--r-- | arch/arm/Kconfig | 26 | ||||
-rw-r--r-- | arch/arm/include/asm/spl.h | 1 | ||||
-rw-r--r-- | arch/arm/lib/Makefile | 2 | ||||
-rw-r--r-- | common/spl/Makefile | 1 | ||||
-rw-r--r-- | common/spl/spl_semihosting.c | 71 |
5 files changed, 96 insertions, 5 deletions
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig index 1f2b849..b2e2873 100644 --- a/arch/arm/Kconfig +++ b/arch/arm/Kconfig @@ -403,11 +403,29 @@ config ARM_SMCCC firmware (for example, PSCI) according to SMCCC. config SEMIHOSTING - bool "support boot from semihosting" + bool "Support ARM semihosting" help - In emulated environments, semihosting is a way for - the hosted environment to call out to the emulator to - retrieve files from the host machine. + Semihosting is a method for a target to communicate with a host + debugger. It uses special instructions which the debugger will trap + on and interpret. This allows U-Boot to read/write files, print to + the console, and execute arbitrary commands on the host system. + + Enabling this option will add support for reading and writing files + on the host system. If you don't have a debugger attached then trying + to do this will likely cause U-Boot to hang. Say 'n' if you are unsure. + +config SPL_SEMIHOSTING + bool "Support ARM semihosting in SPL" + depends on SPL + help + Semihosting is a method for a target to communicate with a host + debugger. It uses special instructions which the debugger will trap + on and interpret. This allows U-Boot to read/write files, print to + the console, and execute arbitrary commands on the host system. + + Enabling this option will add support for reading and writing files + on the host system. If you don't have a debugger attached then trying + to do this will likely cause U-Boot to hang. Say 'n' if you are unsure. config SYS_THUMB_BUILD bool "Build U-Boot using the Thumb instruction set" diff --git a/arch/arm/include/asm/spl.h b/arch/arm/include/asm/spl.h index e568af2..b5790bd 100644 --- a/arch/arm/include/asm/spl.h +++ b/arch/arm/include/asm/spl.h @@ -30,6 +30,7 @@ enum { BOOT_DEVICE_DFU, BOOT_DEVICE_XIP, BOOT_DEVICE_BOOTROM, + BOOT_DEVICE_SMH, BOOT_DEVICE_NONE }; #endif diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile index c48e1f6..594fc12 100644 --- a/arch/arm/lib/Makefile +++ b/arch/arm/lib/Makefile @@ -46,7 +46,7 @@ else obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMSET) += memset.o obj-$(CONFIG_$(SPL_TPL_)USE_ARCH_MEMCPY) += memcpy.o endif -obj-$(CONFIG_SEMIHOSTING) += semihosting.o +obj-$(CONFIG_$(SPL_TPL_)SEMIHOSTING) += semihosting.o obj-y += bdinfo.o obj-y += sections.o diff --git a/common/spl/Makefile b/common/spl/Makefile index db8fd36..e71e7be 100644 --- a/common/spl/Makefile +++ b/common/spl/Makefile @@ -28,6 +28,7 @@ obj-$(CONFIG_$(SPL_TPL_)USB_STORAGE) += spl_usb.o obj-$(CONFIG_$(SPL_TPL_)FS_FAT) += spl_fat.o obj-$(CONFIG_$(SPL_TPL_)FS_EXT4) += spl_ext.o obj-$(CONFIG_$(SPL_TPL_)SATA) += spl_sata.o +obj-$(CONFIG_$(SPL_TPL_)SEMIHOSTING) += spl_semihosting.o obj-$(CONFIG_$(SPL_TPL_)DFU) += spl_dfu.o obj-$(CONFIG_$(SPL_TPL_)SPI_LOAD) += spl_spi.o obj-$(CONFIG_$(SPL_TPL_)RAM_SUPPORT) += spl_ram.o diff --git a/common/spl/spl_semihosting.c b/common/spl/spl_semihosting.c new file mode 100644 index 0000000..df6aeb2 --- /dev/null +++ b/common/spl/spl_semihosting.c @@ -0,0 +1,71 @@ +// SPDX-License-Identifier: GPL-2.0+ +/* + * Copyright (C) 2022 Sean Anderson <sean.anderson@seco.com> + */ + +#include <common.h> +#include <image.h> +#include <log.h> +#include <semihosting.h> +#include <spl.h> + +static int smh_read_full(long fd, void *memp, size_t len) +{ + long read; + + read = smh_read(fd, memp, len); + if (read < 0) + return read; + if (read != len) + return -EIO; + return 0; +} + +static int spl_smh_load_image(struct spl_image_info *spl_image, + struct spl_boot_device *bootdev) +{ + const char *filename = CONFIG_SPL_FS_LOAD_PAYLOAD_NAME; + int ret; + long fd, len; + struct image_header *header = + spl_get_load_buffer(-sizeof(*header), sizeof(*header)); + + fd = smh_open(filename, MODE_READ | MODE_BINARY); + if (fd < 0) { + log_debug("could not open %s: %ld\n", filename, fd); + return fd; + } + + ret = smh_flen(fd); + if (ret < 0) { + log_debug("could not get length of image: %d\n", ret); + goto out; + } + len = ret; + + ret = smh_read_full(fd, header, sizeof(struct image_header)); + if (ret) { + log_debug("could not read image header: %d\n", ret); + goto out; + } + + ret = spl_parse_image_header(spl_image, bootdev, header); + if (ret) { + log_debug("failed to parse image header: %d\n", ret); + goto out; + } + + ret = smh_seek(fd, 0); + if (ret) { + log_debug("could not seek to start of image: %d\n", ret); + goto out; + } + + ret = smh_read_full(fd, (void *)spl_image->load_addr, len); + if (ret) + log_debug("could not read %s: %d\n", filename, ret); +out: + smh_close(fd); + return ret; +} +SPL_LOAD_IMAGE_METHOD("SEMIHOSTING", 0, BOOT_DEVICE_SMH, spl_smh_load_image); |