[U-Boot] [PATCH] distro: load FDT from any partition on boot device

[Rob Clark]

On Thu, Oct 5, 2017 at 8:39 AM, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 04.10.17 22:16, Rob Clark wrote:
>>
>> In the EFI_LOADER boot path, we were only checking the FAT partition
>> containing the EFI payload for dtb files.  But this is somewhat of a
>> fiction.  In reality there will be one small (V)FAT partition containing
>> grub (or whatever the payload may be), and a second boot partition
>> containing kernel/initrd/fdt (typically ext4).  It is this second
>> partition where we should be looking for a FDT to load.
>>
>> So instead scan all the partitions of the disk containing the EFI
>> payload.  This matches where grub looks for kernel/initrd (barring
>> custom grub.cfg, in which case the user can use grub's 'devicetree'
>> command to load the correct FDT).
>>
>> The other option is somehow passing the ${fdtfile} to grub so that it
>> can load the FDT based on selected kernel version location (which grub
>> knows) and SoC/board specific ${fdtfile} (which grub does not know).
>>
>> Signed-off-by: Rob Clark <robdclark at gmail.com>
>> ---
>>   include/config_distro_bootcmd.h | 34 +++++++++++++++++++++++-----------
>>   1 file changed, 23 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/config_distro_bootcmd.h
>> b/include/config_distro_bootcmd.h
>> index e232a62996..58b2fe3371 100644
>> --- a/include/config_distro_bootcmd.h
>> +++ b/include/config_distro_bootcmd.h
>> @@ -126,25 +126,37 @@
>>                 "fi\0"
>> \
>>         \
>>         "load_efi_dtb="
>> \
>> -               "load ${devtype} ${devnum}:${distro_bootpart} "
>> \
>> -                       "${fdt_addr_r} ${prefix}${efi_fdtfile}\0"
>> \
>> +               "load ${devtype} ${devnum}:${dtb_devp} "
>> \
>> +                       "${fdt_addr_r} ${prefix}${efi_fdtfile} && "
>> \
>> +               "run boot_efi_binary\0"
>> \
>>         \
>>         "efi_dtb_prefixes=/ /dtb/ /dtb/current/\0"
>> \
>> -       "scan_dev_for_efi="
>> \
>> +       "scan_dev_for_dtb="
>> \
>>                 "setenv efi_fdtfile ${fdtfile}; "
>> \
>>                 BOOTENV_EFI_SET_FDTFILE_FALLBACK
>> \
>> -               "for prefix in ${efi_dtb_prefixes}; do "
>> \
>> -                       "if test -e ${devtype} "
>> \
>> -                                       "${devnum}:${distro_bootpart} "
>> \
>> -                                       "${prefix}${efi_fdtfile}; then "
>> \
>> -                               "run load_efi_dtb; "
>> \
>> -                       "fi;"
>> \
>> -               "done;"
>> \
>> +               "part list ${devtype} ${devnum} dtb_devplist; "
>> \
>
>
> part list spawns 128 error messages for me on a USB stick with an iso dd'ed
> onto it. I'm not sure we want to do that twice during boot.

I'm not sure how to avoid doing two 'part list's since one we want to
find *all* the partitions, not just the -bootable ones..

I'd suggest you might be better off fixing the root problem here ;-)

>> +               "env exists dtb_devplist || setenv dtb_devplist "
>> \
>> +                       "${distro_bootpart}; "
>> \
>> +               "for dtb_devp in ${dtb_devplist}; do "
>> \
>> +                       "for prefix in ${efi_dtb_prefixes}; do "
>> \
>> +                               "if test -e ${devtype} "
>> \
>> +                                               "${devnum}:${dtb_devp} "
>> \
>> +
>> "${prefix}${efi_fdtfile};"\
>> +                                               " then "
>> \
>> +                                       "echo Found DTB ${devtype} "
>> \
>> +                                               "${devnum}:${dtb_devp} "
>> \
>> +
>> "${prefix}${efi_fdtfile};"\
>> +                                       "run load_efi_dtb; "
>> \
>> +                               "fi;"
>> \
>> +                       "done; "
>> \
>> +               "done; "
>> \
>> +               "run boot_efi_binary\0"
>> \
>
>
> This will run the EFI binary twice if we find a DT on disk. Or really
> nr_dtb_parts_found + 1 times :).

only if the EFI binary returns, which isn't usually going to be the
case for distro boot

That said, if grub scripting supported "break", this would make this much easier

> We also don't want to loop through 50 other partitions if the 1st one
> already contained a dtb. Instead the loop really should end after the first
> successful boot attempt on that device.
>
> (other distro targets should still get boot attempts, you may want to exit
> grub from dhcp to enter grub on scsi).
>
> Furthermore I remember that Andreas worked in that area too before, let's
> make sure to CC him.

If someone has a better patch, then I'm fine to go with that.  I just
needed something to get fedora booting

BR,
-R