On Mon, 9 Dec 2024 at 19:55, Simon Glass <[email protected]> wrote: > The fdt_addr variable is used in extlinux as a fallback devicetree if > none is provided by the boot command. >
And what about where extlinux isn't used? > The existing mechanism uses the devicetree provided to U-Boot, but in > its original, unrelocated position. For the rpi_4 I am using, this is > at 2b35ef00 which is not a convenient place in memory, if the ramdisk > is large. > > U-Boot already deals with this sort of problem by relocating the FDT > to a safe address. > > So use the control-FDT address instead. > Please re-word the above, it doesn't make sense to me, "the rpi_4 I am using" .... what about the other millions of RPis out there? > Remove the existing comment, which is confusing, since the FDT is not > actually passed unmodified to the kernel: U-Boot adds various things > using its FDT-fixup mechanism. > Don't remove it, re-word it so it's up to date. > Note that board_get_usable_ram_top() reduces the RAM top for boards with > less RAM. This behaviour is left unchanged as there is no other > mechanism for U-Boot to handle this. > The below looks irrelevant to the patch at hand, it looks like it should be in the cover letter. > In version 2, it incorporates some changes to fdt_addr, etc. suggested > by Tom, as well as adding myself as a maintainer. > > Signed-off-by: Simon Glass <[email protected]> > --- > > (no changes since v2) > > Changes in v2: > - Drop patch to allow expanding the devicetree during relocation > > board/raspberrypi/rpi/rpi.c | 20 ++++++++------------ > 1 file changed, 8 insertions(+), 12 deletions(-) > > diff --git a/board/raspberrypi/rpi/rpi.c b/board/raspberrypi/rpi/rpi.c > index 9122f33d88d..8f6ab1b1b9b 100644 > --- a/board/raspberrypi/rpi/rpi.c > +++ b/board/raspberrypi/rpi/rpi.c > @@ -3,6 +3,8 @@ > * (C) Copyright 2012-2016 Stephen Warren > */ > > +#define LOG_CATEGORY LOGC_BOARD > + > #include <config.h> > #include <dm.h> > #include <env.h> > @@ -325,19 +327,10 @@ static void set_fdtfile(void) > env_set("fdtfile", fdtfile); > } > > -/* > - * If the firmware provided a valid FDT at boot time, let's expose it in > - * ${fdt_addr} so it may be passed unmodified to the kernel. > - */ > +/* Allow U-Boot to use its control FDT with extlinux if one is not > provided */ > static void set_fdt_addr(void) > { > - if (env_get("fdt_addr")) > - return; > - > - if (fdt_magic(fw_dtb_pointer) != FDT_MAGIC) > - return; > - > - env_set_hex("fdt_addr", fw_dtb_pointer); > + env_set_hex("fdt_addr", (ulong)gd->fdt_blob); > } > > /* > @@ -572,7 +565,10 @@ int ft_board_setup(void *blob, struct bd_info *bd) > { > int node; > > - update_fdt_from_fw(blob, (void *)fw_dtb_pointer); > + if (blob == gd->fdt_blob) > + log_debug("Same FDT: nothing to do\n"); > + else > + update_fdt_from_fw(blob, (void *)gd->fdt_blob); > > node = fdt_node_offset_by_compatible(blob, -1, > "simple-framebuffer"); > if (node < 0) > -- > 2.34.1 > >
