BeagleBone patchset for mainline Linux kernel

After my last post Build fbtft drivers for Linux 4.4 on BeagleBone Black, I was curious watch patches are need to run mainline Linux kernel on BeagleBone Black.  Here’s what I’ve found so far:

Mainline Linux kernel

• “Mainline” refers to Linus Torvald’s linux.git repo hosted on kernel.org:
• Kernel version currently in development is Linux 4.4
• Linux 4.4 is now in the release candidate phase
• Most recent release candidate is: Linux 4.4-rc3

Robert C. Nelson’s bb-kernel repo

• bb-kernel repo is maintained by the most excellent Robert C. Nelson:

“This git repo contains just scripts/patches to build a specific kernel for some ARM devices. The kernel source will be downloaded when you run any of the build scripts”

• Most recent branch is: am33x-v4.4
• Most recent tag: 4.4-rc3-bone0
• build_kernel.sh will clone Linus Torvald’s linux.git repo into ignore/linux-src dir
• The repo in ignore/linux-src will then be cloned into KERNEL dir
• BeagleBone patchset will then be applied to that KERNEL repo

Patchset for BeagleBone:

• Robert maintains a BeagleBone patchset for the mainline Linux kernel
• 102 patches applied when I run the build script
• patch.sh script calls:
  • reverts () function to apply 1 patch
  • ti () function to apply 24 patches for cpu_freq and 3 patches for iodelay
  • pru ()function to apply 2 patches
  • bbb_overlays () function to apply 44 patches
  • beaglebone () function to apply 31 patches
  • quieter () function to apply 1 patch

BeagleBone Cape Manager (bone_capemgr):

• [PATCH 1/5] misc: Beaglebone capemanager by Pantelis Antoniou
• Recent Google+ discussion about mainline and the current bone_capemgr patchset
• eLinux wiki: capemgr
  • in-kernel mechanism for dynamically loading Device Tree fragments from userspace.
  • completely implemented in the kernel with no userspace component
  • implementation is currently located in the BeagleBone kernel patch set at Linux 3.8 and Linux 4.1.
• Device Tree Overlays from bb.org-overlays repo
• slots: /sys/devices/platform/bone_capemgr/slots
• enable/disable cmdline:
  • bone_capemgr.enable_partno=
  • bone_capemgr.disable_partno=

Workaround: Disable DMA for SPI driver:

• bbb: add spi pio mode
  • https://github.com/RobertCNelson/bb-kernel/commit/cef1661f6d27847b7a1f37ab6db2aec397e6388c
• config: CONFIG_SPI_DEBUG is actually useful
  • https://github.com/RobertCNelson/bb-kernel/commit/3596145f3ee2b0ddc7e1832257b1deea4db7afa2
• config: spidev to module
  • https://github.com/RobertCNelson/bb-kernel/commit/37a51d3db7c9ee4a500493ba9a189685dfcfaf7e

Related GitHub Gists:

• bb-kernel am33x-v4.4: patches just bbb_overlays & beaglebone
  • https://gist.github.com/pdp7/f314ba20db5eb2e91d65
• BeagleBone Black am33x-v4.4 with fbtft drivers
  • https://gist.github.com/pdp7/37b3c355ea18e13cfc79