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8e1c9fe243
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>
72 lines
1.5 KiB
C
72 lines
1.5 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright (C) 2022 Sean Anderson <sean.anderson@seco.com>
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*/
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#include <common.h>
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#include <image.h>
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#include <log.h>
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#include <semihosting.h>
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#include <spl.h>
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static int smh_read_full(long fd, void *memp, size_t len)
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{
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long read;
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read = smh_read(fd, memp, len);
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if (read < 0)
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return read;
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if (read != len)
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return -EIO;
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return 0;
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}
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static int spl_smh_load_image(struct spl_image_info *spl_image,
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struct spl_boot_device *bootdev)
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{
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const char *filename = CONFIG_SPL_FS_LOAD_PAYLOAD_NAME;
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int ret;
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long fd, len;
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struct image_header *header =
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spl_get_load_buffer(-sizeof(*header), sizeof(*header));
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fd = smh_open(filename, MODE_READ | MODE_BINARY);
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if (fd < 0) {
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log_debug("could not open %s: %ld\n", filename, fd);
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return fd;
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}
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ret = smh_flen(fd);
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if (ret < 0) {
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log_debug("could not get length of image: %d\n", ret);
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goto out;
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}
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len = ret;
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ret = smh_read_full(fd, header, sizeof(struct image_header));
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if (ret) {
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log_debug("could not read image header: %d\n", ret);
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goto out;
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}
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ret = spl_parse_image_header(spl_image, bootdev, header);
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if (ret) {
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log_debug("failed to parse image header: %d\n", ret);
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goto out;
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}
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ret = smh_seek(fd, 0);
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if (ret) {
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log_debug("could not seek to start of image: %d\n", ret);
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goto out;
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}
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ret = smh_read_full(fd, (void *)spl_image->load_addr, len);
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if (ret)
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log_debug("could not read %s: %d\n", filename, ret);
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out:
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smh_close(fd);
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return ret;
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}
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SPL_LOAD_IMAGE_METHOD("SEMIHOSTING", 0, BOOT_DEVICE_SMH, spl_smh_load_image);
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