Using QEMU how to redirect serial /dev/ttyS2 output of guest machine to host machine.

[Abhishek Singh Dagur]

Thanks, I'll check it out.

On Fri, Mar 17, 2023 at 10:54 PM Cédric Le Goater <clg at kaod.org> wrote:

> On 3/17/23 17:06, Alex Bennée wrote:
> >
> > Abhishek Singh Dagur <abhishek at drut.io> writes:
> >
> > (cc aspeed maintainers)
> >
> >> Hi all,
> >>
> >> We are using obmc-phosphor-image on an ast2500 board which is trying to
> communicate with other devices
> >> over serial port /dev/ttyS2.
> >> As we are trying to emulate the machine on qemu we need to redirect the
> request to the host machine so
> >> that it can handle this request and return appropriately.
> >> We tried using QEMU options like -serial ,-chardev but still not the
> >> concrete way we get to do it.
> >
> > Yeah I'm afraid its non-obvious, certainly for built in serial ports.
> > Try something like:
> >
> >    ./qemu-system-aarch64 -M ast2500-evb \
> >      -serial null -serial null -serial chardev:myserial \
> >      -chardev file,id=myserial,path=output.txt \
> >      $MORE_OPTIONS
> >
> > You have to add a -serial for each serial port up to the one you care
> > about and then set the chardev for it.
> >
> > If you where adding a device to the system then you can explicitly set
> > the target chardev for it with something like:
> >
> >    -device isa-serial,iobase=nnn,irq=nnn,chardev=ID
> >
> >> It will be very helpful if you can provide us some guidance on this.
> >
> > Another quirk for the aspeed boards seems to be the default uart can be
> > an arbitrary one depending on the board model:
> >
> > 334:    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0));
> > 336:        if (uart == amc->uart_default) {
> > 1112:    amc->uart_default = ASPEED_DEV_UART5;
> > 1407:    amc->uart_default = ASPEED_DEV_UART1;
> >
> > as a result ASPEED_DEV_UART5 will always be the first serial port
> > (serial_hd(0)). I don't know how Linux numbers them but worth being
> > aware of.
>
> Yes. UART5 is the general default but it depends on the board definition
> and the fuji was the first to require an exception. See commit 5d63d0c76c
> ("hw/arm/aspeed: Allow machine to set UART default")
>
> Then, it became more complex with commit d2b3eaefb4 ("aspeed: Refactor
> UART init for multi-SoC machines"). That's another topic.
>
> Abhishek,
>
> I am afraid, you will need to add a new board to fit what's in the DT.
>
> Or, here is a little patch adding a machine option to set the default uart.
> It was never merged because it is a bit of hack, give it a try and we
> will discuss. Use :
>
>    -M ast2500-evb,uart-default=uart2
>
>
> Thanks,
>
> C.
>
>  From 0d0700ae772fa5236914e96af1be5afcf0d4a994 Mon Sep 17 00:00:00 2001
> From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= <clg at kaod.org>
> Date: Fri, 17 Mar 2023 18:21:54 +0100
> Subject: [PATCH] aspeed: Add a "uart-default" machine option
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
>
> Signed-off-by: Cédric Le Goater <clg at kaod.org>
> ---
>   hw/arm/aspeed.c | 31 +++++++++++++++++++++++++++++--
>   1 file changed, 29 insertions(+), 2 deletions(-)
>
> diff --git a/hw/arm/aspeed.c b/hw/arm/aspeed.c
> index 806bb10707..e0335cf167 100644
> --- a/hw/arm/aspeed.c
> +++ b/hw/arm/aspeed.c
> @@ -45,6 +45,7 @@ struct AspeedMachineState {
>       bool mmio_exec;
>       char *fmc_model;
>       char *spi_model;
> +    uint32_t uart_default;
>       uint32_t hw_strap1;
>   };
>
> @@ -337,10 +338,11 @@ static void
> connect_serial_hds_to_uarts(AspeedMachineState *bmc)
>       AspeedMachineClass *amc = ASPEED_MACHINE_GET_CLASS(bmc);
>       AspeedSoCState *s = &bmc->soc;
>       AspeedSoCClass *sc = ASPEED_SOC_GET_CLASS(s);
> +    int uart_default = bmc->uart_default ? bmc->uart_default :
> amc->uart_default;
>
> -    aspeed_soc_uart_set_chr(s, amc->uart_default, serial_hd(0));
> +    aspeed_soc_uart_set_chr(s, uart_default, serial_hd(0));
>       for (int i = 1, uart = ASPEED_DEV_UART1; i < sc->uarts_num; i++,
> uart++) {
> -        if (uart == amc->uart_default) {
> +        if (uart == uart_default) {
>               continue;
>           }
>           aspeed_soc_uart_set_chr(s, uart, serial_hd(i));
> @@ -1145,6 +1147,25 @@ static void aspeed_set_spi_model(Object *obj, const
> char *value, Error **errp)
>       bmc->spi_model = g_strdup(value);
>   }
>
> +const QEnumLookup UartDefault_lookup = {
> +    .array =
> +        (const char *const[]) {
> +            [0] = "none",
> +            [1] = "uart1",
> +            [2] = "uart2",
> +            [3] = "uart3",
> +            [4] = "uart4",
> +            [5] = "uart5",
> +        },
> +    .size = 6
> +};
> +
> +static void aspeed_set_uart_default(Object *obj, int val, Error **err)
> +{
> +    AspeedMachineState *bmc = ASPEED_MACHINE(obj);
> +    bmc->uart_default = val + 1;
> +}
> +
>   static void aspeed_machine_class_props_init(ObjectClass *oc)
>   {
>       object_class_property_add_bool(oc, "execute-in-place",
> @@ -1153,6 +1174,12 @@ static void
> aspeed_machine_class_props_init(ObjectClass *oc)
>       object_class_property_set_description(oc, "execute-in-place",
>                              "boot directly from CE0 flash device");
>
> +    object_class_property_add_enum(oc, "uart-default", "UartDefault",
> +                                   &UartDefault_lookup, NULL,
> +                                   aspeed_set_uart_default);
> +    object_class_property_set_description(oc, "uart-default",
> +                           "Change the default UART of the board");
> +
>       object_class_property_add_str(oc, "fmc-model", aspeed_get_fmc_model,
>                                      aspeed_set_fmc_model);
>       object_class_property_set_description(oc, "fmc-model",
> --
> 2.39.2
>
>
>
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