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boot: pxe_utils: skip fdt setup in case legacy kernel is booted

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Currently, if boot with extlinux.conf and do not set the fdt
U-Boot will provide its own device tree. This behavior is
beneficial if the U-Boot device tree is in sync with Linux,
but it totally halts the booting of pre-dtb kernels (3.4 for
example) since it uses ATAGs. To fix this, pass `-` in the
fdt extlinux field as a signal that no tree should be used.

Suggested-by: Jonas Schwöbel <jonasschwoebel@yahoo.de>
Tested-by: Jethro Bull <jethrob@hotmail.com>
Signed-off-by: Svyatoslav Ryhel <clamor95@gmail.com>
This commit is contained in:
Svyatoslav Ryhel 2024-01-25 22:16:54 +02:00 • committed by Tom Rini
parent 172e32add3
commit c95e948870
2 changed files with 28 additions and 5 deletions
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21
boot/pxe_utils.c
View file

@ -634,7 +634,12 @@ static int label_boot(struct pxe_context *ctx, struct pxe_label *label)
char *fdtfilefree = NULL;
if (label->fdt) {
if (IS_ENABLED(CONFIG_SUPPORT_PASSING_ATAGS)) {
if (strcmp("-", label->fdt))
fdtfile = label->fdt;
} else {
fdtfile = label->fdt;
}
} else if (label->fdtdir) {
char *f1, *f2, *f3, *f4, *slash;
@ -731,14 +736,26 @@ static int label_boot(struct pxe_context *ctx, struct pxe_label *label)
zboot_argc = 5;
}
if (!bootm_argv[3])
if (!bootm_argv[3]) {
if (IS_ENABLED(CONFIG_SUPPORT_PASSING_ATAGS)) {
if (strcmp("-", label->fdt))
bootm_argv[3] = env_get("fdt_addr");
} else {
bootm_argv[3] = env_get("fdt_addr");
}
}
kernel_addr_r = genimg_get_kernel_addr(kernel_addr);
buf = map_sysmem(kernel_addr_r, 0);
if (!bootm_argv[3] && genimg_get_format(buf) != IMAGE_FORMAT_FIT)
if (!bootm_argv[3] && genimg_get_format(buf) != IMAGE_FORMAT_FIT) {
if (IS_ENABLED(CONFIG_SUPPORT_PASSING_ATAGS)) {
if (strcmp("-", label->fdt))
bootm_argv[3] = env_get("fdtcontroladdr");
} else {
bootm_argv[3] = env_get("fdtcontroladdr");
}
}
if (bootm_argv[3]) {
if (!bootm_argv[2])

6
doc/develop/distro.rst
View file

@ -81,6 +81,12 @@ as specified at `Boot Loader Specification`_:
* Does not document the fdtdir option, which automatically selects the DTB to
pass to the kernel.
* If no fdt/fdtdir is provided, the U-Boot will pass its own currently used
device tree.
* If ``-`` is passed as fdt argument and ``CONFIG_SUPPORT_PASSING_ATAGS`` is
enabled, then no device tree will be used (legacy booting / pre-dtb kernel).
See also doc/README.pxe under 'pxe file format'.
One example extlinux.conf generated by the Fedora installer is::