Hi Tushar, > Here is my assessment of the current situation. Thanks for digging into this and the detailed diagnosis. > *Bug in the u-boot* > Current u-boot for Arndale-octa board has defined NR_BANKS as 12 and the > core uses a global structure (gd->bd) to maintain the start and size of > individual banks. Depending on the revision of SoC used on the board, > the board file [1] updates the start/size for either 8 or 12 banks. In > case of current revision of Arndale-Octa boards, the board file always > updates start/size for 8 banks, leaving the start/size data for > remaining 4 banks uninitialized. > > But the u-boot core[2] updates the value of all the 12 banks, thus > potentially updating invalid data for last 4 banks. > > The issue can be fixed by resetting the start/size for unused memory > banks to 0/0.[3] > > *Before migration to memblock* > The path for adding DRAM banks was done through [4]. For Exynos systems, > NR_BANKS was defined as 8. The initial check for rejecting any banks > beyond NR_BANKS was good enough for fixing this issue. The bootlog[5] > (with some debug messages) shows the invalid data, both in u-boot and > kernel. Please grep for "NR_BANKS too low, ignoring memory" in the bootlog. > > *After migration to memblock* > Now that the memory banks are added through [6], all the memory banks > are getting updated unconditionally resulting in the panic. > > IMO, the bug is in u-boot and we should fix that. I agree that the u-boot bug needs to be fixed, and FWIW, I updated my u-boot and haven't seen the boot failure yet after several boots with next-20140625. That being said, since it's not always feasible/practical to update u-boot, and when it comes down to it, this is still a kernel regression, we should also fix the kernel to sanity check the values coming from u-boot, like it was doing before. Could you (or Laura) come up with a way to recreate the sanity check that was detecting this problem before and ignoring those banks? Thanks, Kevin -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
 |