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 --- boot/pxe_utils.c | 27 ++++++++++++++++++++++----- doc/develop/distro.rst | 6 ++++++ 2 files changed, 28 insertions(+), 5 deletions(-)

diff --git a/boot/pxe_utils.c b/boot/pxe_utils.c index 83bc167785..9620562675 100644 --- a/boot/pxe_utils.c +++ b/boot/pxe_utils.c @@ -634,7 +634,12 @@ static int label_boot(struct pxe_context *ctx, struct pxe_label *label) char *fdtfilefree = NULL;

if (label->fdt) { - fdtfile = 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]) - bootm_argv[3] = env_get("fdt_addr"); + 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) - bootm_argv[3] = env_get("fdtcontroladdr"); + 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]) diff --git a/doc/develop/distro.rst b/doc/develop/distro.rst index 8016acad09..9e715b23eb 100644 --- a/doc/develop/distro.rst +++ b/doc/develop/distro.rst @@ -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::