[U-Boot] [RFC] disk: part_dos: Fix part_test_dos() regression

[Rob Clark]

On Tue, Oct 3, 2017 at 6:47 AM, Rob Clark <robdclark at gmail.com> wrote:
> personally I think we should try to figure out what is wrong on imx6
> rather than blindly reverting.. without this change MBR partitioned
> disks might not generate unique device-paths for EFI boot.
>
> If you can't get any debug logs from SPL build, perhaps you can try an
> old SPL image but main u-boot image with the logs I suggested?  I
> guess the same issue should happen with the main u-boot image.
>
> BR,
> -R
>
> On Mon, Oct 2, 2017 at 9:50 PM, Fabio Estevam <festevam at gmail.com> wrote:
>> From: Fabio Estevam <fabio.estevam at nxp.com>
>>
>> Since commit ff98cb90514d ("part: extract MBR signature from partitions")
>> SPL boot on i.MX6 starts to fail:
>>
>> U-Boot SPL 2017.09-00221-g0d6ab32 (Oct 02 2017 - 15:13:19)
>> Trying to boot from MMC1
>> (hangs here)
>>
>> Revert the part_test_dos() changes from this commit, so that
>> SPL boot can be functional again.
>>
>> Tested on a imx6q-cuboxi board.
>>
>> Signed-off-by: Fabio Estevam <fabio.estevam at nxp.com>
>> ---
>>  disk/part_dos.c | 10 ++--------
>>  1 file changed, 2 insertions(+), 8 deletions(-)
>>
>> diff --git a/disk/part_dos.c b/disk/part_dos.c
>> index 1a36be0..213a8d8 100644
>> --- a/disk/part_dos.c
>> +++ b/disk/part_dos.c
>> @@ -89,20 +89,14 @@ static int test_block_type(unsigned char *buffer)
>>
>>  static int part_test_dos(struct blk_desc *dev_desc)
>>  {
>> -       ALLOC_CACHE_ALIGN_BUFFER(legacy_mbr, mbr, dev_desc->blksz);
>> +       ALLOC_CACHE_ALIGN_BUFFER(unsigned char, mbr, dev_desc->blksz);

btw, if I had to take a guess, I'd say that perhaps blksz is smaller
than 'legacy_mbr', so maybe rather than allocating blksize, it should
be DIV_ROUND_UP(sizeof(legacy_mbr), dev_desc->blksz).. or I guess that
could be simplified to not use division if blksz is a power of two

BR,
-R


>>
>>         if (blk_dread(dev_desc, 0, 1, (ulong *)mbr) != 1)
>>                 return -1;
>>
>> -       if (test_block_type((unsigned char *)mbr) != DOS_MBR)
>> +       if (test_block_type(mbr) != DOS_MBR)
>>                 return -1;
>>
>> -       if (dev_desc->sig_type == SIG_TYPE_NONE &&
>> -           mbr->unique_mbr_signature != 0) {
>> -               dev_desc->sig_type = SIG_TYPE_MBR;
>> -               dev_desc->mbr_sig = mbr->unique_mbr_signature;
>> -       }
>> -
>>         return 0;
>>  }
>>
>> --
>> 2.7.4
>>