Re: [Xen-users] Help on passthrough serial device to BareMetal DOMU

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxx>]

On Tue, 30 Jul 2019, Julien Grall wrote:
> (+ Stefano)
> 
> Hi,
> 
> On 26/07/2019 16:35, Sarah Newman wrote:
> > On 7/26/19 7:27 AM, Jan Cordes wrote:
> > > Hello everybody,
> > > 
> > > we are fairly new to XEN and have a few questions regarding our XEN
> > > setup on Xilinx ZCU102 Board. We want to pass through the UART1 device
> > > to a bare metal guest. The way Xilinx proposed in their documentation to
> > > XEN BareMetal Guests is to add the following via an .dtsi file to the
> > > device tree:
> > > 
> > > &&uart1 {
> > >     xen,passthrough = <0x1>;
> > > };

Yes, this is the only change required to the host device tree (with only
one '&'). You can also add "xen,passthrough = <0x1>;" by hand under the
uart node that you want to assign to the baremetal guest:

        serial@ff010000 {
            u-boot,dm-pre-reloc;
            compatible = "cdns,uart-r1p12", "xlnx,xuartps";
            status = "okay";
            interrupt-parent = <0x4>;
            interrupts = <0x0 0x16 0x4>;
            reg = <0x0 0xff010000 0x0 0x1000>;
            clock-names = "uart_clk", "pclk";
            power-domains = <0x26 0x22>;
            clocks = <0x3 0x39 0x3 0x1f>;
            pinctrl-names = "default";
            pinctrl-0 = <0x38>;
            cts-override;
            device_type = "serial";
            port-number = <0x1>;
            xen,passthrough = <0x1>;
        };

and recompile the device tree with:

dtc -I dts -O dtb mpsoc.dts > mpsoc.dtb


> > > Unfortunately, this does not work for us, we don't get any output on our
> > > serial console.
> > > 
> > > We are using the config file which was provided by xilinx:
> > > 
> > > 
> > > #Guest name
> > >    name = "hello_world"
> > > # Kernel image to boot
> > >    kernel = "xapp_hello_world_el1.bin"
> > > # Kernel command line options - Allocate 8MB
> > >    memory = 8
> > > # Number of VCPUS
> > >    vcpus = 1
> > > # Pin to CPU 0
> > >    cpus = [1]
> > >    irqs = [ 54 ]
> > >    iomem = [ "0xff010,1" ]
> > > 
> > > Maybe someone can give a few tips, which steps are necessary to pass a
> > > device to a bare metal DOMU, or point out where we missed something.

This is correct.

My guess is that the device tree change above wasn't applied correctly
somehow?

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