Re: Using a custom device tree file

[Rainer Dorsch <ml@bokomoko.de>]

Hi Vagrant,

I want to use a modified dts file for a Hummingboard, I do enable spidev for 
the spi interfaces:

What I did so far is I created a new file:

rd@master:/mnt/disk/scratch/rd$ diff -u ./debian/kernel/linux-source-4.14/
arch/arm/boot/dts/imx6q-hummingboard.dts ./debian/kernel/linux-source-4.14/
arch/arm/boot/dts/imx6q-hummingboard-spi.dts
--- ./debian/kernel/linux-source-4.14/arch/arm/boot/dts/imx6q-hummingboard.dts  
2018-01-10 09:31:23.000000000 +0100
+++ ./debian/kernel/linux-source-4.14/arch/arm/boot/dts/imx6q-hummingboard-
spi.dts      2018-02-18 21:29:20.870755691 +0100
@@ -45,7 +45,7 @@
 #include "imx6qdl-hummingboard.dtsi"
 
 / {
-       model = "SolidRun HummingBoard Dual/Quad";
+       model = "SolidRun HummingBoard Dual/Quad spidev enabled";
        compatible = "solidrun,hummingboard/q", "fsl,imx6q";
 };
 
@@ -56,3 +56,36 @@
        fsl,transmit-atten-16ths = <9>;
        fsl,receive-eq-mdB = <3000>;
 };
+
+&ecspi2 {
+       fsl,spi-num-chipselects = <2>;
+       cs-gpios = <&gpio2 26 1>, <&gpio2 27 1>;
+       pinctrl-names = "default";
+       pinctrl-0 = <&pinctrl_hummingboard_spi>;
+       status = "okay";
+       spidev@0x00 {
+               compatible = "spidev";
+               spi-max-frequency = <5000000>;
+               reg = <0>;
+       };
+       spidev@0x01 {
+               compatible = "spidev";
+               spi-max-frequency = <5000000>;
+               reg = <1>;
+       };
+};
+
+
+&iomuxc {
+       hummingboard {
+               pinctrl_hummingboard_spi: hummingboard_spi {
+                       fsl,pins = <
+                               MX6QDL_PAD_EIM_OE__ECSPI2_MISO   0x100b1
+                               MX6QDL_PAD_EIM_CS1__ECSPI2_MOSI  0x100b1
+                               MX6QDL_PAD_EIM_CS0__ECSPI2_SCLK  0x100b1
+                               MX6QDL_PAD_EIM_RW__GPIO2_IO26    0x80000000
+                               MX6QDL_PAD_EIM_LBA__GPIO2_IO27   0x80000000
+                       >;
+               };
+       };
+};
rd@master:/mnt/disk/scratch/rd$

and build a new dtb and copied it to 

# cp arch/arm/boot/dts/imx6dl-hummingboard-spi.dtb /boot/dtbs/4.14.0-3-armmp/

and copied it to imx6q-hummingboard.dtb (i.e. overwrote the old supplied dtb 
after making a copy of it).

Introducing a new model name was probably not a good idea, since it breaks the 
upgrade, so I try to go back to the unmodified model name. Then after each 
kernel upgrade I need to go through the manual procedure of rebuilding a new 
modified dtb file.... do you see a better way to keep spidev enabled?

Thanks
Rainer

On Donnerstag, 8. März 2018 02:04:02 CEST Vagrant Cascadian wrote:
> On 2018-02-19, Rainer Dorsch wrote:
> > Am Samstag, 17. Februar 2018, 16:22:06 CET schrieb Vagrant Cascadian:
> >> > Can anybody tell, if it is possible to configure from u-boot shell to
> >> > loada
> >> > custom device treefile?
> >> 
> >> To manually change it for a one-off boot:
> >>   # disable the built-in setting of fdtfile
> >>   setenv findfdt
> >>   # manually set fdtfile
> >>   setenv fdtfile /path/to/your/custom.dtb
> > 
> > Where is findfdt defined?
> 
> In the built-in u-boot environment on some boards. Typically with u-boot
> variants that can support multiple similar boards; a single mx6cuboxi
> u-boot binary supports several cubox-i and hummingboard variants.
> 
> It's typically run from bootcmd, so "printenv bootcmd" from the u-boot
> prompt might show something like "run findfdt ; run distro_bootcmd".
> 
> >>From looking into the bootscr fdtfile needs only the filename:
> > if test -n "${fdtfile}"; then
> > 
> >    setenv fdtpath dtbs/${fk_kvers}/${fdtfile}
> > 
> > else
> > 
> >    setenv fdtpath dtb-${fk_kvers}
> > 
> > fi
> > 
> > Correct?
> 
> Ah, yes, full path wouldn't work in this case- you'd have to have it in
> one of the above locations the boot scripts look for.
> 
> 
> live well,
>   vagrant


-- 
Rainer Dorsch
http://bokomoko.de/