[PATCH] serial/lpuart: Do not enable UART FIFO

[Sascha Hauer]

On Thu, Apr 12, 2018 at 02:41:43PM -0700, Andrey Smirnov wrote:
> Using FIFO in LPUART results in subtle serial input draining issues
> which are quite difficult to reproduce and troubleshoot. Since the
> change offered only moderate performance gain revert the code to
> operate in no-FIFO mode to avoid FIFO-related problems alltogether.
> 
> Signed-off-by: Andrey Smirnov <andrew.smirnov at gmail.com>

Applied, thanks

Sascha

> ---
>  drivers/serial/serial_lpuart.c |  4 +---
>  include/serial/lpuart.h        | 21 +++++----------------
>  2 files changed, 6 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/serial/serial_lpuart.c b/drivers/serial/serial_lpuart.c
> index 52fb6d39c..8f87f7b9c 100644
> --- a/drivers/serial/serial_lpuart.c
> +++ b/drivers/serial/serial_lpuart.c
> @@ -170,9 +170,7 @@ static int lpuart_serial_probe(struct device_d *dev)
>  
>  	cdev->linux_console_name = "ttyLP";
>  
> -	lpuart_setup_with_fifo(lpuart->base,
> -			       clk_get_rate(lpuart->clk),
> -			       15);
> +	lpuart_setup(lpuart->base, clk_get_rate(lpuart->clk));
>  
>  	ret = console_register(cdev);
>  	if (!ret) {
> diff --git a/include/serial/lpuart.h b/include/serial/lpuart.h
> index 917f644a5..a920291de 100644
> --- a/include/serial/lpuart.h
> +++ b/include/serial/lpuart.h
> @@ -238,22 +238,17 @@ static inline void lpuart_setbrg(void __iomem *base,
>  	writeb(bfra, base + UARTCR4);
>  }
>  
> -static inline void lpuart_setup_with_fifo(void __iomem *base,
> -					  unsigned int refclock,
> -					  unsigned int twfifo)
> +static inline void lpuart_setup(void __iomem *base,
> +				unsigned int refclock)
>  {
>  	/* Disable UART */
>  	writeb(0, base + UARTCR2);
>  	writeb(0, base + UARTMODEM);
>  	writeb(0, base + UARTCR1);
>  
> -	if (twfifo) {
> -		writeb(UARTPFIFO_TXFE | UARTPFIFO_RXFE, base + UARTPFIFO);
> -		writeb((u8)twfifo, base + UARTTWFIFO);
> -	} else {
> -		writeb(0, base + UARTPFIFO);
> -		writeb(0, base + UARTTWFIFO);
> -	}
> +	writeb(0, base + UARTPFIFO);
> +	writeb(0, base + UARTTWFIFO);
> +
>  	writeb(1, base + UARTRWFIFO);
>  	writeb(UARTCFIFO_RXFLUSH | UARTCFIFO_TXFLUSH, base + UARTCFIFO);
>  
> @@ -262,12 +257,6 @@ static inline void lpuart_setup_with_fifo(void __iomem *base,
>  	writeb(UARTCR2_TE | UARTCR2_RE, base + UARTCR2);
>  }
>  
> -static inline void lpuart_setup(void __iomem *base,
> -				unsigned int refclock)
> -{
> -	lpuart_setup_with_fifo(base, refclock, 0x00);
> -}
> -
>  static inline void lpuart_putc(void __iomem *base, int c)
>  {
>  	if (!(readb(base + UARTCR2) & UARTCR2_TE))
> -- 
> 2.14.3
> 
> 
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> 

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