ARC: U-boot: check arguments paranoidly
Handle U-boot arguments paranoidly:
* don't allow to pass unknown tag.
* try to use external device tree blob only if corresponding tag
(TAG_DTB) is set.
* don't check uboot_tag if kernel build with no ARC_UBOOT_SUPPORT.
NOTE:
If U-boot args are invalid we skip them and try to use embedded device
tree blob. We can't panic on invalid U-boot args as we really pass
invalid args due to bug in U-boot code.
This happens if we don't provide external DTB to U-boot and
don't set 'bootargs' U-boot environment variable (which is default
case at least for HSDK board) In that case we will pass
{r0 = 1 (bootargs in r2); r1 = 0; r2 = 0;} to linux which is invalid.
While I'm at it refactor U-boot arguments handling code.
Cc: stable at vger.kernel.org
Tested-by: Corentin LABBE <clabbe at baylibre.com>
Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev at synopsys.com>
Signed-off-by: Vineet Gupta <vgupta at synopsys.com>
UnifiedSplitRaw
