[PATCH] debug-8250: add a 32 bit mode

[Jamie Iles]

On Mon, Nov 22, 2010 at 02:51:42PM +0000, Jamie Iles wrote:
> Some platforms such as picoChip picoXCell devices can only do 32 bit
> accesses to APB peripherals. If the platform defines
> DEBUG_8250_ACCESS_32 before including debug-8250.S in debug-macros.S
> then use 32-bit accesses for senduart, busyuart and waituart. If not
> defined, use 8-bit accesses.
> 
> Signed-off-by: Jamie Iles <jamie at jamieiles.com>

Any opinions on this patch? I'm not entirely happy with the way I've 
done it, but the alternatives are:

	1. Create a new debug-8250-32bit.S with ldr/str
	2. Move this into the platform

(1) involves duplicating the code and extra maintenance (although 
debug-8250 hasn't been touched much) and (2) could be useful to other 
platforms in the future.

I'm happy to rework in any form though.

Jamie

> ---
> 
> Note: for the TTY support we also need
> [8250: add a UPIO_DWAPB32 for 32 bit accesses (v2)] at
> http://marc.info/?l=linux-serial&m=129043658715199&w=2
> 
>  arch/arm/include/asm/hardware/debug-8250.S |   21 ++++++++++++++++++---
>  1 files changed, 18 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/include/asm/hardware/debug-8250.S b/arch/arm/include/asm/hardware/debug-8250.S
> index 22c6892..71f0839 100644
> --- a/arch/arm/include/asm/hardware/debug-8250.S
> +++ b/arch/arm/include/asm/hardware/debug-8250.S
> @@ -9,12 +9,26 @@
>   */
>  #include <linux/serial_reg.h>
>  
> +/*
> + * Some platforms may only be able to perform 32-bit accesses to peripherals
> + * on an APB bus. If this is the case, define DEBUG_8250_ACCESS_32 before
> + * including this file.
> + */
> +#ifdef DEBUG_8250_ACCESS_32
> +# define ldr_uart    ldr
> +# define str_uart    str
> +#else /* DEBUG_8250_ACCESS_32 */
> +# define ldr_uart    ldrb
> +# define str_uart    strb
> +#endif /* DEBUG_8250_ACCESS_32 */
> +
>  		.macro	senduart,rd,rx
> -		strb	\rd, [\rx, #UART_TX << UART_SHIFT]
> +                and     \rd, \rd, #0xff
> +		str_uart    \rd, [\rx, #UART_TX << UART_SHIFT]
>  		.endm
>  
>  		.macro	busyuart,rd,rx
> -1002:		ldrb	\rd, [\rx, #UART_LSR << UART_SHIFT]
> +1002:		ldr_uart    \rd, [\rx, #UART_LSR << UART_SHIFT]
>  		and	\rd, \rd, #UART_LSR_TEMT | UART_LSR_THRE
>  		teq	\rd, #UART_LSR_TEMT | UART_LSR_THRE
>  		bne	1002b
> @@ -22,7 +36,8 @@
>  
>  		.macro	waituart,rd,rx
>  #ifdef FLOW_CONTROL
> -1001:		ldrb	\rd, [\rx, #UART_MSR << UART_SHIFT]
> +1001:		ldr_uart    \rd, [\rx, #UART_MSR << UART_SHIFT]
> +                and     \rd, \rd, 0xff
>  		tst	\rd, #UART_MSR_CTS
>  		beq	1001b
>  #endif
> -- 
> 1.7.2.3
>