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

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

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

Is the shift 2 on Baozi's platform too? Perhaps this could be a #define
provided in the same style as EARLY_UART_BASE_ADDRESS or via some other
means?

The definitions themselves duplicate those in
xen/drivers/char/ns16550.c, perhaps we could refactor those into a
suitable header?

> +
> +#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:
> + */



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