[PATCH] MIPS: DEBUG_LL_UART_DIVISOR is 0, use a0 instead

[Ahmad Fatoum]

Hello Du,

On 9/25/20 6:42 PM, Du Huanpeng wrote:
> Hi, How about this, I send this for review, if it is ok,
> I will send a patch later.
> 
> I add a argument to the macro, and set a default parameter.
> 
> +.macro	debug_ll_ns16550_init divisor=DEBUG_LL_UART_DIVISOR

Sounds great! Much less error prone IMO.

> 
> 
> +	/* three forms for ``call'' the macro */
> pass a register name
> +	debug_ll_ns16550_init v0
> 
> pass a immediate number
> +	debug_ll_ns16550_init 888
> 
> use this macro as usual before
> +	debug_ll_ns16550_init
> 
> ----8<-----
> 
> diff --git a/arch/mips/boards/loongson-ls1b/lowlevel.S b/arch/mips/boards/loongson-ls1b/lowlevel.S
> index af6ad54e1..7120d80ef 100644
> --- a/arch/mips/boards/loongson-ls1b/lowlevel.S
> +++ b/arch/mips/boards/loongson-ls1b/lowlevel.S
> @@ -28,8 +28,14 @@ ENTRY_FUNCTION(BOARD_PBL_START)
>  
>  	pbl_loongson1_uart_enable
>  	pbl_loongson1_calc_prescale 115200
> -	move	a0, v0
> +
> +	/* three forms for ``call'' the macro */
> +	debug_ll_ns16550_init v0
> +	debug_ll_ns16550_init 888
> +	debug_ll_ns16550_init
> +
>  	debug_ll_ns16550_init
> +
>  	debug_ll_ns16550_outnl
>  	debug_ll_outc '.'
>  	debug_ll_ns16550_outnl
> diff --git a/arch/mips/include/asm/debug_ll_ns16550.h b/arch/mips/include/asm/debug_ll_ns16550.h
> index a33587a15..44f3d5976 100644
> --- a/arch/mips/include/asm/debug_ll_ns16550.h
> +++ b/arch/mips/include/asm/debug_ll_ns16550.h
> @@ -58,17 +58,14 @@ static inline void PUTC_LL(char ch)
>   * Macros for use in assembly language code
>   */
>  
> -.macro	debug_ll_ns16550_init
> +.macro	debug_ll_ns16550_init divisor=DEBUG_LL_UART_DIVISOR
>  #ifdef CONFIG_DEBUG_LL
>  	la	t0, DEBUG_LL_UART_ADDR
>  
>  	li	t1, UART_LCR_DLAB		/* DLAB on */
>  	sb	t1, UART_LCR(t0)		/* Write it out */
>  
> -	li	t1, DEBUG_LL_UART_DIVISOR
> -#if DEBUG_LL_UART_DIVISOR == 0
> -	move	t1, a0
> -#endif
> +	add	t1, zero, \divisor
>  	sb	t1, UART_DLL(t0)		/* write low order byte */
>  	srl	t1, t1, 8
>  	sb	t1, UART_DLM(t0)		/* write high order byte */
> 

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