On 9/6/19 4:29 pm, Vijay Kumar Banerjee wrote: > On Sun, Jun 9, 2019 at 6:22 AM Chris Johns <chr...@rtems.org > <mailto:chr...@rtems.org>> wrote: > On 8/6/19 5:58 pm, Christian Mauderer wrote: > > ----- Ursprüngliche Mail ----- > >> Von: "Oyake, Amalaye (386M)" <amalaye.oy...@jpl.nasa.gov > <mailto:amalaye.oy...@jpl.nasa.gov>> > >> An: "Chris Johns" <chr...@rtems.org <mailto:chr...@rtems.org>>, "Vijay > Kumar Banerjee" <vijaykumar9...@gmail.com > <mailto:vijaykumar9...@gmail.com>>, "Christian Mauderer" > >> <christian.maude...@embedded-brains.de > <mailto:christian.maude...@embedded-brains.de>> > >> CC: "RTEMS Users" <users@rtems.org <mailto:users@rtems.org>> > >> Gesendet: Samstag, 8. Juni 2019 04:57:02 > >> Betreff: Re: [EXTERNAL] Re: BeagleBone Black Networking (wifi and/or > wired) > > > >> Device Tree overays are a method used to update the Device Tree. Given > a > device > >> tree that describes all the devices, let's say you add a new SPI > device, you > >> can update the device tree with a (blob) device tree overlay. > >> > >> I should ask (without Googling), What is the Device Tree Overlay > mechanism in > >> RTEMS? > > > > > > Hello Amalaye, > > > > as far as I know, the device tree overlay mechanism in RTEMS is not > implemented. There is the prototype of fdt_overlay_apply() in libfdt.h but > there is no implementation. So there are two methods: > > > > 1. Applying the overlay on a build machine. Vijay did that during his > tests. > > How do you do this? > > I used `fdtoverlay` from libfdt on linux host.
Could cpukit/dtc/libfd in RTEMS be updated to support this code? I see freebsd's kernel has the code. > > > 2. Use the U-Boot mechanism to apply overlays before booting RTEMS. That > should most likely work too. But I didn't test it yet. > > OK > > >> On 6/7/19, 6:17 PM, "users on behalf of Chris Johns" > <users-boun...@rtems.org <mailto:users-boun...@rtems.org> on > >> behalf of chr...@rtems.org <mailto:chr...@rtems.org>> wrote: > >> > >> On 8/6/19 1:53 am, Vijay Kumar Banerjee wrote: > >> > > >> > I would like to add that in two projects of this year( I2C and > PRU-ICSS drivers) > >> > we > >> > are using our own device tree overlays that make our drivers work. > Where to add > >> > the device > >> > tree related stuff seems like an important question. > >> > >> What are device tree overlays? > > > > Like Oyake already said: They are some small pices of device trees that > are just added to the base tree in it's binary form. Linux (and most > likely > FreeBSD too) supports that even after boot. If you add an overlay it > re-parses the device tree, updates GPIO settings and loads new drivers. > The > alternative is to let the boot loader apply them during boot. > > What is needed to do this? Maybe I can add it to rtems-boot-image as a > way to > handle this at the u-boot version. > > I have also tried to automate it by adding it in uEnv.txt as a script, it > worked > nicely to apply > the overlay on the blob, I haven't tested it with any app though, but the > overlay applied > successfully. Here's what the test uEnv.txt looks like. > ``` > setenv bootdelay 5 > uenvcmd=run overlay_cmd boot > overlay_cmd=fatload mmc 0 0x80800000 rtems-app.img; fatload mmc 0 0x88000000 > am335x-boneblack.dtb; fatload mmc 0 0x88100000 am335x-rtems.dtbo; fdt addr > 0x88000000; fdt resize 0x1000; fdt apply 0x88100000; > boot=bootm 0x80800000 - 0x88000000; > ``` > > You can add something like this to the uEnv.txt in SD card image. In the above > script > the am335x-boneblack.dtb is the one from linux and am335x-rtems.dtbo is > generated > with dtc from the overlay written by me. Ah I see. I think this could be added to rtems-boot-image. There is something attractive about building the fdt at run time on the board from the needed pieces. Chris _______________________________________________ users mailing list users@rtems.org http://lists.rtems.org/mailman/listinfo/users
