[PATCH 4/4] serial: serial_xen: add DEBUG_UART support

[Peng Fan]

> Subject: [PATCH 4/4] serial: serial_xen: add DEBUG_UART support
> 
> By using a hypervisor call, we can implement DEBUG_UART on xen.
> This will allow us to see messages even earlier than serial_init().
> 
> Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
> ---
>  drivers/serial/Kconfig      | 14 +++++++++++---
>  drivers/serial/serial_xen.c | 20 ++++++++++++++++++++
>  2 files changed, 31 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig index
> e344677f91f6..536cf0641773 100644
> --- a/drivers/serial/Kconfig
> +++ b/drivers/serial/Kconfig
> @@ -401,11 +401,19 @@ config DEBUG_UART_MTK
>  	  driver will be available until the real driver model serial is
>  	  running.
> 
> +config DEBUG_UART_XEN
> +	bool "XEN Hypervisor Console"
> +	depends on XEN_SERIAL
> +	help
> +	  Select this to enable a debug UART using the serial_xen driver. You
> +	  will not have to provide any parameters to make this work. The driver
> +          will be available until the real driver-model serial is running.

Please add one more line that it needs XEN debug enabled. without xen debug,
you will not able to see any outputs.

Regards,
Peng.

> +
>  endchoice
> 
>  config DEBUG_UART_BASE
>  	hex "Base address of UART"
> -	depends on DEBUG_UART
> +	depends on DEBUG_UART && !DEBUG_UART_XEN
>  	default 0 if DEBUG_UART_SANDBOX
>  	help
>  	  This is the base address of your UART for memory-mapped UARTs.
> @@ -415,7 +423,7 @@ config DEBUG_UART_BASE
> 
>  config DEBUG_UART_CLOCK
>  	int "UART input clock"
> -	depends on DEBUG_UART
> +	depends on DEBUG_UART && !DEBUG_UART_XEN
>  	default 0 if DEBUG_UART_SANDBOX
>  	help
>  	  The UART input clock determines the speed of the internal UART @@
> -427,7 +435,7 @@ config DEBUG_UART_CLOCK
> 
>  config DEBUG_UART_SHIFT
>  	int "UART register shift"
> -	depends on DEBUG_UART
> +	depends on DEBUG_UART && !DEBUG_UART_XEN
>  	default 0 if DEBUG_UART
>  	help
>  	  Some UARTs (notably ns16550) support different register layouts diff
> --git a/drivers/serial/serial_xen.c b/drivers/serial/serial_xen.c index
> ed191829f059..34c90ece40fc 100644
> --- a/drivers/serial/serial_xen.c
> +++ b/drivers/serial/serial_xen.c
> @@ -5,6 +5,7 @@
>   */
>  #include <common.h>
>  #include <cpu_func.h>
> +#include <debug_uart.h>
>  #include <dm.h>
>  #include <serial.h>
>  #include <watchdog.h>
> @@ -15,11 +16,14 @@
>  #include <xen/events.h>
> 
>  #include <xen/interface/sched.h>
> +#include <xen/interface/xen.h>
>  #include <xen/interface/hvm/hvm_op.h>
>  #include <xen/interface/hvm/params.h>
>  #include <xen/interface/io/console.h>
>  #include <xen/interface/io/ring.h>
> 
> +#include <asm/xen/hypercall.h>
> +
>  DECLARE_GLOBAL_DATA_PTR;
> 
>  u32 console_evtchn;
> @@ -178,3 +182,19 @@ U_BOOT_DRIVER(serial_xen) = {
>  	.flags			= DM_FLAG_PRE_RELOC,
>  };
> 
> +#if defined(CONFIG_DEBUG_UART_XEN)
> +static inline void _debug_uart_init(void) {}
> +
> +static inline void _debug_uart_putc(int c) { #if CONFIG_IS_ENABLED(ARM)
> +	xen_debug_putc(c);
> +#else
> +	/* the type cast should work on LE only */
> +	HYPERVISOR_console_io(CONSOLEIO_write, 1, (char *)&ch); #endif }
> +
> +DEBUG_UART_FUNCS
> +
> +#endif
> --
> 2.28.0