Re: [PATCH] serial: Use -EAGAIN in getc and putc

[Stefan Roese <sr@denx.de>]

On 12/4/22 13:36, Pali Rohár wrote:
> U-Boot serial code already handles -EAGAIN value from getc and putc
> callbacks. So change drivers code to return -EAGAIN when HW is busy instead
> of doing its own busy loop and waiting until HW is ready.
> 
> Signed-off-by: Pali Rohár <pali@kernel.org>

Reviewed-by: Stefan Roese <sr@denx.de>

Thanks,
Stefan

> ---
>   drivers/serial/serial_arc.c         | 8 ++++----
>   drivers/serial/serial_lpuart.c      | 8 ++++----
>   drivers/serial/serial_mvebu_a3700.c | 8 ++++----
>   3 files changed, 12 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/serial/serial_arc.c b/drivers/serial/serial_arc.c
> index b2d95bdbe18d..c2fc8a901e25 100644
> --- a/drivers/serial/serial_arc.c
> +++ b/drivers/serial/serial_arc.c
> @@ -53,8 +53,8 @@ static int arc_serial_putc(struct udevice *dev, const char c)
>   	struct arc_serial_plat *plat = dev_get_plat(dev);
>   	struct arc_serial_regs *const regs = plat->reg;
>   
> -	while (!(readb(&regs->status) & UART_TXEMPTY))
> -		;
> +	if (!(readb(&regs->status) & UART_TXEMPTY))
> +		return -EAGAIN;
>   
>   	writeb(c, &regs->data);
>   
> @@ -83,8 +83,8 @@ static int arc_serial_getc(struct udevice *dev)
>   	struct arc_serial_plat *plat = dev_get_plat(dev);
>   	struct arc_serial_regs *const regs = plat->reg;
>   
> -	while (!arc_serial_tstc(regs))
> -		;
> +	if (!arc_serial_tstc(regs))
> +		return -EAGAIN;
>   
>   	/* Check for overflow errors */
>   	if (readb(&regs->status) & UART_OVERFLOW_ERR)
> diff --git a/drivers/serial/serial_lpuart.c b/drivers/serial/serial_lpuart.c
> index ff576da516d4..d7259d531b55 100644
> --- a/drivers/serial/serial_lpuart.c
> +++ b/drivers/serial/serial_lpuart.c
> @@ -168,8 +168,8 @@ static void _lpuart_serial_setbrg(struct udevice *dev,
>   static int _lpuart_serial_getc(struct lpuart_serial_plat *plat)
>   {
>   	struct lpuart_fsl *base = plat->reg;
> -	while (!(__raw_readb(&base->us1) & (US1_RDRF | US1_OR)))
> -		schedule();
> +	if (!(__raw_readb(&base->us1) & (US1_RDRF | US1_OR)))
> +		return -EAGAIN;
>   
>   	barrier();
>   
> @@ -181,8 +181,8 @@ static void _lpuart_serial_putc(struct lpuart_serial_plat *plat,
>   {
>   	struct lpuart_fsl *base = plat->reg;
>   
> -	while (!(__raw_readb(&base->us1) & US1_TDRE))
> -		schedule();
> +	if (!(__raw_readb(&base->us1) & US1_TDRE))
> +		return -EAGAIN;
>   
>   	__raw_writeb(c, &base->ud);
>   }
> diff --git a/drivers/serial/serial_mvebu_a3700.c b/drivers/serial/serial_mvebu_a3700.c
> index 0fcd7e88acee..b2017c645565 100644
> --- a/drivers/serial/serial_mvebu_a3700.c
> +++ b/drivers/serial/serial_mvebu_a3700.c
> @@ -40,8 +40,8 @@ static int mvebu_serial_putc(struct udevice *dev, const char ch)
>   	struct mvebu_plat *plat = dev_get_plat(dev);
>   	void __iomem *base = plat->base;
>   
> -	while (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
> -		;
> +	if (readl(base + UART_STATUS_REG) & UART_STATUS_TXFIFO_FULL)
> +		return -EAGAIN;
>   
>   	writel(ch, base + UART_TX_REG);
>   
> @@ -53,8 +53,8 @@ static int mvebu_serial_getc(struct udevice *dev)
>   	struct mvebu_plat *plat = dev_get_plat(dev);
>   	void __iomem *base = plat->base;
>   
> -	while (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
> -		;
> +	if (!(readl(base + UART_STATUS_REG) & UART_STATUS_RX_RDY))
> +		return -EAGAIN;
>   
>   	return readl(base + UART_RX_REG) & 0xff;
>   }

Viele Grüße,
Stefan Roese

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