Re: [Xen-devel] [PATCH V2 2/2] xen: arm: implement early prink for 8250 uart

[Chen Baozi <baozich@xxxxxxxxx>]

On Tue, 2013-07-02 at 21:11 +0800, Bamvor Jian Zhang wrote:

> implement early printk for 8250 uart which is used by lots of arm SOC, such as
> Allwinner A31(sun6i) and OMAP5432.
> 
> Signed-off-by: Bamvor Jian Zhang <bjzhang@xxxxxxxx>
> ---
>  docs/misc/arm/early-printk.txt    |  1 +
>  xen/arch/arm/Rules.mk             |  5 ++++
>  xen/arch/arm/arm32/debug-8250.inc | 48 
> +++++++++++++++++++++++++++++++++++++++
>  3 files changed, 54 insertions(+)
>  create mode 100644 xen/arch/arm/arm32/debug-8250.inc
> 
> diff --git a/docs/misc/arm/early-printk.txt b/docs/misc/arm/early-printk.txt
> index fbc3208..eaa66a1 100644
> --- a/docs/misc/arm/early-printk.txt
> +++ b/docs/misc/arm/early-printk.txt
> @@ -13,6 +13,7 @@ where mach is the name of the machine:
>    - exynos5250: printk with the second UART
>    - midway: printk with the pl011 on Calxeda Midway processors
>    - fastmodel: printk on ARM Fastmodel software emulators
> +  - sun6i: printk with 8250 on Allwinner A31 processors
Could this be better to add:

    - omap5432: printk with 8250 compatible UART on OMAP5432 processors

>  
>  The base address and baud rate is hardcoded in xen/arch/arm/Rules.mk,
>  see there when adding support for new machines.
> diff --git a/xen/arch/arm/Rules.mk b/xen/arch/arm/Rules.mk
> index 422ed04..51e823d 100644
> --- a/xen/arch/arm/Rules.mk
> +++ b/xen/arch/arm/Rules.mk
> @@ -64,6 +64,11 @@ EARLY_PRINTK_INC := pl011
>  EARLY_PRINTK_BAUD := 115200
>  EARLY_UART_BASE_ADDRESS := 0xfff36000
>  endif
> +ifeq ($(CONFIG_EARLY_PRINTK), sun6i)
> +# uart configured at 115200 by bootloader
> +EARLY_PRINTK_INC := 8250
> +EARLY_UART_BASE_ADDRESS := 0x01c28000
> +endif

EARLY_UART_BASE_ADDRESS on OMAP5432 is 0x48020000, so I think we'd better to 
add another case to support it? For example:

+ifeq ($(CONFIG_EARLY_PRINTK), omap5432)
+# uart configured at 115200 by bootloader
+EARLY_PRINTK_INC := 8250
+EARLY_UART_BASE_ADDRESS := 0x48020000
+endif


>  
>  ifneq ($(EARLY_PRINTK_INC),)
>  EARLY_PRINTK := y
> diff --git a/xen/arch/arm/arm32/debug-8250.inc 
> b/xen/arch/arm/arm32/debug-8250.inc
> new file mode 100644
> index 0000000..c11357d
> --- /dev/null
> +++ b/xen/arch/arm/arm32/debug-8250.inc
> @@ -0,0 +1,48 @@
> +/*
> + * xen/arch/arm/arm32/debug-8250.inc
> + *
> + * 8250 specific debug code
> + *
> + * Bamvor Jian Zhang <bjzhang@xxxxxxxx>
> + * Copyright (c) 2013 SUSE
> + *
> + * 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.
> + */
> +
> +
> +#define UART_TX           (0x00<<2)    /* Out: Transmit buffer */
> +#define UART_LSR          (0x05<<2)    /* In:  Line Status Register */
> +
> +#define UART_LSR_THRE     0x20         /* Xmit holding register empty */
> +
> +/* 8250 UART wait UART to be ready to transmit
> + * rb: register which contains the UART base address
> + * rc: scratch register */
> +.macro early_uart_ready rb, rc
> +1:
> +        ldr   \rc, [\rb, #UART_LSR]    /* <- UART_LSR (Line Status Register) 
> */
> +        tst   \rc, #UART_LSR_THRE      /* Check BUSY bit */
> +        beq   1b                       /* Wait for the UART to be ready */
> +.endm
> +
> +/* 8250 UART transmit character
> + * rb: register which contains the UART base address
> + * rt: register which contains the character to transmit */
> +.macro early_uart_transmit rb, rt
> +        str   \rt, [\rb, #UART_TX]     /* -> UART_TX */
> +.endm
> +
> +/*
> + * Local variables:
> + * mode: ASM
> + * indent-tabs-mode: nil
> + * End:
> + */
> -- 
> 1.8.1.4

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