On 11/29/2015 11:40 AM, Marco Schuster wrote: > On Raspberry Pi, the primary bootloader start.elf uses the options in > config.txt, as well as options hidden in the firmware itself, to tell > the Linux kernel e.g. framebuffer sizes, memory regions, MAC addresses > and more.
Was this patch sent using "git send-email"? I assume not, since it is corrupted due to wrapping. I suspect ./scripts/checkpatch.pl also wasn't run, since it would complain about over-long lines, and multiple other formatting errors. > Normally, u-boot would not be able to pass through these options to > the Linux kernel. This patch adds pass-through support via an > additional env variable "bootargs_orig" which is loaded with the > original cmdline obtained from ATAG or the FDT. > > In addition, this allows the user to configure DT overlays the "Pi > way" by enabling them in config.txt, as this patch passes through the > full FDT if it has been passed one by u-boot. > > Note that, as stated in the comment block, for FDT passthrough to > work, the u-boot.img must be run through a perl script by the > Raspberry Pi Foundation, which appends a trailer to the image telling > start.elf to supply a FDT instead of an ATAG struct. This feature sounds fine. However, it should be optional. It likely only makes sense when booting a downstream Pi Foundation kernel, and not when booting an upstream/mainline kernel with matching DT using the standardized DT bindings. As such, I think this feature should be optional (e.g. perhaps en-/dis-abled by an environment variable at run-time) so that the user gets to choose whether to use the feature. > diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c > index 6451d1d..d8d0fbb 100644 > --- a/board/raspberrypi/rpi/rpi.c > +++ b/board/raspberrypi/rpi/rpi.c > @@ -259,6 +259,72 @@ int misc_init_r(void) > #ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG > set_board_info(); > #endif > + > + /* > + * The RPi start.elf passes important system configuration > + * like memory sizes and LED GPIO assignments to the kernel > + * via kernel command line. > + * > + * Therefore we have to parse the passed ATAG or FDT to get the s/have to/may/ > + * commandline and pass it through to script-land via the env > + * variable "bootargs_orig" so it can be passed on. > + * > + * By default, start.elf assumes a non-DT capable kernel and > + * passes the commandline via ATAG; this requires u-boot to > + * load the FDT from /boot and pass it on. This works if no > + * overlays have been passed through, but once overlays are in > + * the mix, stuff gets complicated to do in u-boot. Ideally, DT overlays would be either implemented in U-Boot, or deferred until the kernel boots and user-space can load overlays. I suspect the latter is more inline with the usage model expected by upstream/mainline, although I haven't checked to see. > + * > + * To force start.elf to pass a processed, ready-to-go DT, > + * you have to use the mkknlimg tool on the u-boot image: > + * ./mkknlimg --dtok u-boot.bin /boot/u-boot.bin > + * > + * mkknlimg can be obtained from > https://github.com/raspberrypi/tools/blob/master/mkimage/knlinfo > + * > + * User scripts can check for successful bootargs retrieval > + * in the env variable pi_bootmode, which is either fdt, atag > + * or unknown in case of an error. > + * > + * The location 0x100 is hard-coded in start.elf, and it is > + * the same as in the default bootscripts, so you only have > + * to omit the fatload command loading the raw FDT to get > + * going. "omit the fatload command" from where? Personally I've been using extlinux.conf on my Pi for a while, so there is no "fatload" anywhere that I'm aware of. > + */ > + > + void* ptr = (char*) 0x100; > + struct tag_header* atag_ptr = ptr; > + setenv("pi_bootmode","unknown"); > + > + if(atag_ptr->tag != ATAG_CORE) { > + if(atag_ptr->size == be32_to_cpu(FDT_MAGIC)) { > + set_working_fdt_addr((ulong) ptr); Doesn't that set the address of the DT that U-Boot uses to configure itself, not the DT that U-Boot will pass to the kernel? The two are certainly separate concepts. This code should set $fdt_addr/$fdt_addr_r if the DT is detected, so that scripts can affect whether this DT is used. > + int nodeoffset = fdt_path_offset(working_fdt, > "/chosen"); > + int len; > + const void* nodep = fdt_getprop(working_fdt, > nodeoffset, "bootargs", &len); > + if(len==0) { > + printf("WARNING: Could not determine > bootargs from FDT!\n"); > + } else { > + printf("Set bootargs_orig from FDT\n"); debug() seems more appropriate than printf(), except for errors. > + setenv("bootargs_orig", (char*) nodep); > + setenv("pi_bootmode","fdt"); > + } > + } else { > + printf("Warning: start.elf did not pass ATAG > or FDT parameters\n"); > + } > + } else { > + while(atag_ptr->tag != ATAG_NONE) { > + printf("at %p, have %x (len > %x)\n",atag_ptr,atag_ptr->tag, atag_ptr->size); > + if(atag_ptr->tag == ATAG_CMDLINE) { > + char* old_cmdline = ptr + 8; > + printf("Set bootargs_orig from ATAG\n"); > + setenv("bootargs_orig", old_cmdline); > + setenv("pi_bootmode", "atag"); > + } > + ptr = ptr + (atag_ptr->size * 4); > + atag_ptr=ptr; > + } > + } > + > return 0; > } _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
