I had been running Kernel 4.6-rc2 on the Radxa Rock2 without any issues, and decided to update to recently-released Kernel 4.6-rc4..
Brief details of changes from -rc3 are here: http://lkml.iu.edu/hypermail/linux/kernel/1604.2/00610.html
The boot failed, and I then compiled/installed 4.6-rc3 to see if that would have been OK, and it was..
I then noticed something odd in the failed boot process… It appeared that the MMC device references had swapped around in -rc4:
RC3 – and earlier (boot OK):
........... mmc0: new high speed SDXC card at address e624 mmcblk1: mmc0:e624 SL64G 59.5 GiB mmcblk1: p1 ...........
RC4 (boot failed):
........... mmc0: new high speed SDXC card at address e624 mmcblk0: mmc0:e624 SL64G 59.5 GiB mmcblk0: p1 ...........
So… a simple change to the u-boot kernel boot command – changing root=/dev/mmcblk1p1 to root=/dev/mmcblk0p1 – fixed the problem, and 4.6-rc4 booted OK..
Fedora 23 (Twenty Three) Kernel 4.6.0-rc4 on an armv7l (ttyS2) ............... ]# uname -a Linux rgrock2 4.6.0-rc4 #1 SMP Wed Apr 20 18:44:57 EDT 2016 armv7l armv7l armv7l GNU/Linux
All that was needed then, was to change /etc/fstab accordingly.. (Yes – I still use the ‘traditional’ format!)
Initial investigation suggested that this might be the kernel patch responsible: http://lkml.iu.edu/hypermail/linux/kernel/1604.0/04340.html
On the Rock2, this means that the on-board eMMC is now /dev/mmcblk1, and the SDcard is /dev/mmcblk0… It will be interesting to see if this change affects any of my other ARM devices…..
Robert Gadsdon. April 20, 2016.