How to add custom dts entries

[Bernd Walter]

On Sun, Nov 04, 2018 at 07:53:38PM +0100, Bernd Walter wrote:
> On Sun, Nov 04, 2018 at 07:49:39PM +0100, Bernd Walter wrote:
> > On Sun, Nov 04, 2018 at 07:32:47PM +0100, Bernd Walter wrote:
> > > On Sat, Nov 03, 2018 at 03:25:38PM -0600, Ian Lepore wrote:
> > > > Add a status = "okay" to the spi node in your patch/overlay.
> > > 
> > > Makes sense.
> > > 
> > > So the spigen overlay works fine, once I set fdt_overlays in loader.conf
> > > to use the overlay file.
> > > 
> > > spi0: <BCM2708/2835 SPI controller> mem 0x7e204000-0x7e204fff irq 25 on simplebus0
> > > spibus0: <OFW SPI bus> on spi0
> > > spibus0: <unknown card> at cs 1 mode 0
> > > spibus0: <unknown card> at cs 0 mode 0
> > > spibus0: <unknown card> at cs 0 mode 0
> > > spibus0: <unknown card> at cs 1 mode 0
> > > 
> > > With my own overlay I do this to install it:
> > > dtc -I dts -O dtb -o rpi-apa102-matrix.dtbo rpi-apa102-matrix.dts
> > > cp rpi-apa102-matrix.dtbo /boot/dtb/overlays
> > > 
> > > [77]cicely1> cat rpi-apa102-matrix.dts
> > > /dts-v1/;
> > > /plugin/;
> > > 
> > > / {
> > >         compatible = "brcm,bcm2835";
> > > };
> > > 
> > > /* &spi0 { */
> > > &{/soc/spi at 7e204000} {
> > >         status = "okay";
> > > 
> > >         apa102led0 {
> > >                 compatible = "led,apa102";
> > >                 reg = <0>;
> > >                 spi-max-frequency = <20000000>;
> > >                 status = "okay";
> > >         };
> > > };
> > > 
> > > &onewire {
> > >         compatible = "w1-gpio";
> > >         gpios = <&gpio 4 1>;
> > > };
> > > 
> > > Still puzzled with the format.
> > > With &spi0 it didn't work, neither with the current format, which is
> > > copied from the spigen.dts.
> > > Neither spi0 attaches, nor the onewire bus.
> > > 
> > > Some other, mostly beaglebone related examples use a more complex
> > > setup with overlay_ entries and everything inside the compatible block.
> > > 
> > > Can I have a device.hints please ;-)
> > > 
> > > ofwdump shows:
> > > ...
> > >     Node 0x20fc: spi at 7e204000
> > >       compatible:
> > >         62 72 63 6d 2c 62 63 6d 32 38 33 35 2d 73 70 69 00 
> > >         'brcm,bcm2835-spi'
> > > ...
> > >       status:
> > >         64 69 73 61 62 6c 65 64 00 
> > >         'disabled'
> > > ...
> > > 
> > > Havn't checked ofwdump with the spigen overlay.
> > 
> > Interesting.
> > When I use &spi0 and leave out the &onewire block, it attaches something.
> > spi0: <BCM2708/2835 SPI controller> mem 0x7e204000-0x7e204fff irq 25 on simplebus0
> > spibus0: <OFW SPI bus> on spi0
> > spibus0: <unknown card> at cs 0 mode 0
> > spibus0: <unknown card> at cs 0 mode 0
> > spibus0: <unknown card> at cs 1 mode 0
> > 
> > And also my driver attaches just fine:
> > apa102led0: <APA102> at cs 0 mode 0 on spibus0
> > 
> > And ofwdump shows the spi0 es enabled:
> >     Node 0x20fc: spi at 7e204000
> >       compatible:
> >         62 72 63 6d 2c 62 63 6d 32 38 33 35 2d 73 70 69 00 
> >         'brcm,bcm2835-spi'
> > ...
> >       status:
> >         6f 6b 61 79 00 
> >         'okay'
> > ...
> > 
> > I'm not on the real hardware, so no LED connected to test the driver.
> > It would probably also attach with the &{/soc/spi at 7e204000}.
> > But why does the &onewire entry make such a difference?
> > Is the whole file revoked because of an error?
> > I have no console connected, so I don't see loader messages.
> > 
> > Also it is a bit puzzling about the "unknown card" entries.
> 
> Ah ok.
> Those 4 with the spigen driver are 2 devices defined by the generic DTS,
> plus 2 devices from the spigen overlay - the spigen module wasn't laoded.
> Same for my overlay, 2 generic, plus my LED definition.
>       spi0 pnpinfo name=spi at 7e204000 compat=brcm,bcm2835-spi
>         spibus0
>           apa102led0 pnpinfo name=apa102led0 compat=led,apa102 at bus=0 cs=0
>           unknown pnpinfo name=spidev at 0 compat=spidev at bus=0 cs=0
>           unknown pnpinfo name=spidev at 1 compat=spidev at bus=0 cs=1
> 
> Makes sense.

Ok, no surprise that &onewire can't work if it isn't defined yet.

owc0: <FDT GPIO attached one-wire bus> at pin 4 on gpiobus0
ow0: <1 Wire Bus> on owc0
ow0: Reset discovered bus wired wrong.
gpioc0: <GPIO controller> on gpio0
uart0: <PrimeCell UART (PL011)> mem 0x7e201000-0x7e201fff irq 23 on simplebus0
uart0: console (115200,n,8,1)
spi0: <BCM2708/2835 SPI controller> mem 0x7e204000-0x7e204fff irq 25 on simplebus0
spibus0: <OFW SPI bus> on spi0
apa102led0: <APA102> at cs 0 mode 0 on spibus0
spibus0: <unknown card> at cs 0 mode 0
spibus0: <unknown card> at cs 1 mode 0

With the following dts:
[96]cicely1> cat rpi-apa102-matrix.dts
/dts-v1/;
/plugin/;

&spi0 {
        status = "okay";

        apa102led0 {
                compatible = "led,apa102";
                reg = <0>;
                spi-max-frequency = <20000000>;
                status = "okay";
        };
};

/ {
        fragment at 0 {
                target-path = "/";
                __overlay__ {
                        onewire {
                                compatible = "w1-gpio";
                                gpios = <&gpio 4 1>;
                        };
                };
        };
};

I tried the same without the fragment and overlay blocks, but it didn't
work.
Why does it work for the spi0?

Have to put the SD card into the real system to see if the spi and the onewire
works.
So far everything looks fine, although I don't exactly know why.
I understand that I would have to setup the CS pin for normal spi use.

-- 
B.Walter <bernd at bwct.de> http://www.bwct.de
Modbus/TCP Ethernet I/O Baugruppen, ARM basierte FreeBSD Rechner uvm.