[PATCH v2 0/2] Fix boot failure due to misaligned DMA buffer

[Nam Cao]

Hi,

We observed the following sporadic boot failure while booting from MMC
device:

=> boot
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
CACHE: Misaligned operation at range [9efa25f8, 9efa27f8]
** Booting bootflow 'mmc at 2194000.bootdev.part_1' with extlinux
Ignoring unknown command: �D���D��
Boot failed (err=-14)

The reason is because while allocating buffer to read a file from MMC,
alignment of 1 byte is used. Thus, the buffer doesn't work for performing
DMA, and garbage data is read.

While looking at this issue, I also noticed that if no alignment specified
(align=0) then fs_read_alloc() is documented to use the default. But the
default is no alignment. Therefore, other users of fs_read_alloc() which
specify align=0 may be broken as well.

The first patch changes extlinux_read_bootflow() to use proper buffer
alignment for DMA.

The second patch changes the default alignment of fs_read_alloc() to be
DMA-suitable, to fix other potential bugs.

Nam Cao (2):
  boot: extlinux: Fix unaligned buffer for reading data from file system
  fs: Use ARCH_DMA_MINALIGN as default alignment for fs_read_alloc()

 boot/bootmeth_extlinux.c | 3 ++-
 fs/fs.c                  | 4 ++++
 include/fs.h             | 2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

-- 
2.39.5