On 9/3/20 2:14 PM, Dennis Gilmore wrote:
> On Thu, Sep 3, 2020 at 2:15 PM Stephen Warren <swar...@wwwdotorg.org> wrote:
>>
>> On 9/3/20 10:40 AM, Dennis Gilmore wrote:
>>> When testing builds provided in https://github.com/openwrt/openwrt/pull/3360
>>> I discovered that fdtfile was not set and as a result the firmware was not
>>> functional. So I am documenting what is needed.
>>>
>>> Signed-off-by: Dennis Gilmore <den...@ausil.us>
>>>
>>> Cc: Atish Patra <atish.pa...@wdc.com>
>>> Cc: Lukas Auer <lukas.a...@aisec.fraunhofer.de>
>>> Cc: Tom Rini <tr...@konsulko.com>
>>> Cc: Masahiro Yamada <yamada.masah...@socionext.com>
>>> Cc: Vagrant Cascadian <vagr...@debian.org>
>>> Cc: Stephen Warren <swar...@nvidia.com>
>>> Cc: Karsten Merker <mer...@debian.org>
>>> ---
>>> doc/README.distro | 8 ++++++++
>>> 1 file changed, 8 insertions(+)
>>>
>>> diff --git a/doc/README.distro b/doc/README.distro
>>> index 5076bebd18..3eb70aeb14 100644
>>> --- a/doc/README.distro
>>> +++ b/doc/README.distro
>>> @@ -224,6 +224,14 @@ fdt_addr_r:
>>>
>>> A size of 1MB for the FDT/DTB seems reasonable.
>>>
>>> +fdtfile:
>>> +
>>> + Mandatory. the name of the DTB file for the specific board for instance
>>> + the espressobin v5 board the value is
>>> "marvell/armada-3720-espressobin.dtb"
>>> + while on a clearfog pro it is "armada-388-clearfog-pro.dtb" in the case
>>> of
>>> + a board providing its firmware based DTB this value can be used to
>>> override
>>> + the DTB with a different DTB.
>>
>> IIRC this variable isn't mandatory; if the DT filename follows expected
>> ${soc}-${board}.dtb naming, then U-Boot has a default value that will
>> work without the user or U-Boot author having to manually set this variable.
>>
>> So it's certainly mandatory that U-Boot know this value at runtime, but
>> perhaps the text should be expanded to indicate that sometimes U-Boot
>> can provide the value itself, but sometimes the variable needs to be set?
>
> in include/config_distro_bootcmd.h we have the following
> /*
> * On 32bit ARM systems there is a reasonable number of systems that follow
> * the $soc-$board$boardver.dtb name scheme for their device trees. Use that
> * scheme if we don't have an explicit fdtfile variable.
> */
> #define BOOTENV_EFI_SET_FDTFILE_FALLBACK \
> "if test -z \"${fdtfile}\" -a -n \"${soc}\"; then " \
> "setenv efi_fdtfile ${soc}-${board}${boardver}.dtb; " \
> "fi; "
> #else
> #define BOOTENV_EFI_SET_FDTFILE_FALLBACK
> #endif
>
> that schema is not true on AArch64 and the method only works with efi
> booting. I will update the text to list out the conditions you could
> get away with not setting the variable
I was thinking more of cmd/pxe_utils.c:label_boot(), which covers the
extlinux.conf rather then EFI case. This certainly applies to both 32-
and 64-bit Tegra systems at least.
Specifically:
> f1 = env_get("fdtfile");
> if (f1) {
> f2 = "";
> f3 = "";
> f4 = "";
> } else {
> /*
> * For complex cases where this code doesn't
> * generate the correct filename, the board
> * code should set $fdtfile during early boot,
> * or the boot scripts should set $fdtfile
> * before invoking "pxe" or "sysboot".
> */
> f1 = env_get("soc");
> f2 = "-";
> f3 = env_get("board");
> f4 = ".dtb";
> }
