Re: [Xen-devel] [RFC 18/29] xen/arm: add generic UART to get the device in the device tree

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-04-29 at 00:02 +0100, Julien Grall wrote:
> This generic UART will find the right UART via xen command line
> with com1=myserial.
> 
> "myserial" is the alias of the UART in the device tree. Xen will retrieve
> the information via the device tree and call the initialization function for
> this specific UART thanks to the device API.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> ---
>  xen/arch/arm/setup.c        |    3 +-
>  xen/drivers/char/Makefile   |    1 +
>  xen/drivers/char/arm-uart.c |   76 
> +++++++++++++++++++++++++++++++++++++++++++
>  xen/include/xen/serial.h    |    8 +++++
>  4 files changed, 87 insertions(+), 1 deletion(-)
>  create mode 100644 xen/drivers/char/arm-uart.c
> 
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 51f4bba..e5d8724 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -434,8 +434,9 @@ void __init start_xen(unsigned long boot_phys_offset,
>  #ifdef EARLY_UART_ADDRESS
>      /* TODO Need to get device tree or command line for UART address */
>      pl011_init(0, FIXMAP_ADDR(FIXMAP_CONSOLE));
> -    console_init_preirq();
>  #endif
> +    arm_uart_init();
> +    console_init_preirq();
>  
>      /* FIXME: Do something smarter */
>      dt_switch_to_printk();
> diff --git a/xen/drivers/char/Makefile b/xen/drivers/char/Makefile
> index ab2246d..e68a54a 100644
> --- a/xen/drivers/char/Makefile
> +++ b/xen/drivers/char/Makefile
> @@ -2,4 +2,5 @@ obj-y += console.o
>  obj-$(HAS_NS16550) += ns16550.o
>  obj-$(HAS_PL011) += pl011.o
>  obj-$(HAS_EHCI) += ehci-dbgp.o
> +obj-$(CONFIG_ARM) += arm-uart.o
>  obj-y += serial.o
> diff --git a/xen/drivers/char/arm-uart.c b/xen/drivers/char/arm-uart.c
> new file mode 100644
> index 0000000..e242ae2
> --- /dev/null
> +++ b/xen/drivers/char/arm-uart.c
> @@ -0,0 +1,76 @@
> +/*
> + * xen/drivers/char/arm-uart.c
> + *
> + * Generic ARM uart retrieved via the device tree
> + *
> + * Julien Grall <julien.grall@xxxxxxxxxx>
> + * Copyright (c) 2013 Linaro Limited.
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + */
> +
> +#include <asm/device.h>
> +#include <asm/early_printk.h>
> +#include <asm/types.h>
> +#include <xen/console.h>
> +#include <xen/device_tree.h>
> +#include <xen/mm.h>
> +#include <xen/serial.h>
> +
> +/*
> + * Configure serial port with string: devname
> + * Where devname is the alias of the device in the device tree
> + */
> +static char __initdata opt_com1[30] = "";
> +string_param("com1", opt_com1);

com1 is a bit of an x86-ism. Can we use e.g. uart0 or does common code
constrain us here?

Better would be to arrange things such that console=myserial does the
lookup. Then myserial=<foo> sets options for that device.

I think you would need to add a call to dt_console_init to
console_init_preirq(), in the "Where should console output go?" loop.

Ian.


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