KernelDriverProgrammingCourse2015/OutlineDay1

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Revision as of 17:27, 25 July 2015 by Hans de Goede (talk | contribs) (Kernel Driver Programming Course Day 1)
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Kernel Driver Programming Course Day 1

  1. Intro
    1. Welcome
    2. I'm going to dump a lot of information on you, don't worry you do not need to remember it all :)
    3. Quickly explain of different Axx models
    4. A10 Datasheet Block diagram (page 12), give a quick overview of the A10
  2. A10 SoC dtsi file (example)
    1. sun4i-a10.dtsi
    2. For a list of addresses see the A10 user manual, section 3.2 "Memory mapping", and 11.2 "Interrupt Source"
    3. For clock tree info see: A10 Datasheet Clock tree diagram (pages 51 - 54)
  3. dts file example for a simple board
    1. sun4i-a10-mini-xplus.dts
    2. fex file for the mini-x board
  4. Hands on 1: Build and install u-boot and a dts file and boot the board
    1. Everyone gets a board, a usb to serial convertor and a sdcard
    2. Build and install u-boot:
      1. Figure out the config to use for your board, do:
        cd u-boot
        grep -l SUNXI configs/*_defconfig
      2. Build u-boot for your board, do:
        make -j4 CROSS_COMPILE=arm-linux-gnu- $foo_defconfig
        make -j4 CROSS_COMPILE=arm-linux-gnu-
      3. Insert the provided sdcard into your laptop
      4. Figure out which blockdev it has been given, do:
        dmesg | tail
      5. Install u-boot by dd-ing it to the whole device (not a partition) blockdev, e.g.:
        sudo dd if=u-boot-sunxi-with-spl.bin of=/dev/sdc bs=1024 seek=8
    3. Boot the board:
      1. Plug a usb to serial convertor into your laptop
      2. Figure out which ttyUSB# it has been given, do:
        dmesg | tail
      3. Start screen on the ttyUSB# in question, e.g.:
        screen /dev/ttyUSB0 115200
      4. Power up the board, and check that it boots properly in the screen session
    4. Build and install your own dts file:
      1. Edit the dts file for your board:
        cd linux
        $editor arch/arm/boot/dts/sun?i-a??-$board.dts
      2. At the top of the file you will see e.g. "model = "PineRiver Mini X-Plus"; This is a free format string, change the model string to something else, e.g. "Hans' test board" and then save the file
      3. Now build a dtb file from the dts file:
        make -j4 ARCH=arm CROSS_COMPILE=arm-linux-gnu- dtbs
      4. Then install the dtb file, insert the sdcard into your laptop, mount the first partition of it, and copy arch/arm/boot/dts/sun?i-a*-*.dtb to the dtb directory, e.g.:
        sudo cp -pr arch/arm/boot/dts/sun?i-*.dtb /run/media/hans/__boot/dtb/
      5. Boot the board again, login and do:
        cat /sys/firmware/devicetree/base/model
        to verify that your modified dtb file is being used
  5. Adding support for the musb otg controller to a sunxi dts file
    1. See the commit enabling it on the A20 OLinuxino Lime as an example of the necessary changes
    2. See the A20 OLinuxino Lime schematic as an example how to figure out which gpios to use for vbus_det / id_det. Or alternatively look at the usbc0 section of the fex file for the board.
    3. Some boards are special and use the pmic instead of a gpio for vbus-det, see e.g. the bananapi fex file. For an example of how to deal with this in the dts file see the commit enabling the otg controller on the bananapi.
    4. Quick demo of how to test otg on a sunxi board
  6. Hands on 2: Enable the otg controller on the board you've
    1. Modify the dts file for your board in the same way as done in the provided examples
    2. Build and install the dts file as before
    3. Test the otg controller as demoed