[PATCH 1/8] serial: imx: factor-out common code to imx_uart_soft_reset()

[Ilpo Järvinen]

On Fri, 13 Jan 2023, Sergey Organov wrote:

> We perform soft reset in 2 places, slightly differently for no sufficient
> reasons, so move more generic variant to a function, and re-use the code.
> 
> Out of 2 repeat counters, 10 and 100, select 10, as the code works at
> interrupts disabled, and in practice the reset happens immediately.
> 
> Signed-off-by: Sergey Organov <sorganov at gmail.com>
> ---
>  drivers/tty/serial/imx.c | 73 ++++++++++++++++++++--------------------
>  1 file changed, 37 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
> index 757825edb0cd..bf222d8568a9 100644
> --- a/drivers/tty/serial/imx.c
> +++ b/drivers/tty/serial/imx.c
> @@ -397,6 +397,39 @@ static void start_hrtimer_ms(struct hrtimer *hrt, unsigned long msec)
>         hrtimer_start(hrt, ms_to_ktime(msec), HRTIMER_MODE_REL);
>  }
>  
> +/* called with port.lock taken and irqs off */
> +static void imx_uart_soft_reset(struct imx_port *sport)
> +{
> +	int i = 10;
> +	u32 ucr2, ubir, ubmr, uts;
> +
> +	/*
> +	 * According to the Reference Manual description of the UART SRST bit:
> +	 *
> +	 * "Reset the transmit and receive state machines,
> +	 * all FIFOs and register USR1, USR2, UBIR, UBMR, UBRC, URXD, UTXD
> +	 * and UTS[6-3]".
> +	 *
> +	 * We don't need to restore the old values from USR1, USR2, URXD and
> +	 * UTXD. UBRC is read only, so only save/restore the other three
> +	 * registers.
> +	 */
> +	ubir = imx_uart_readl(sport, UBIR);
> +	ubmr = imx_uart_readl(sport, UBMR);
> +	uts = imx_uart_readl(sport, IMX21_UTS);
> +
> +	ucr2 = imx_uart_readl(sport, UCR2);
> +	imx_uart_writel(sport, ucr2 & ~UCR2_SRST, UCR2);
> +
> +	while (!(imx_uart_readl(sport, UCR2) & UCR2_SRST) && (--i > 0))
> +		udelay(1);

This could use read_poll_timeout_atomic().

-- 
 i.


> +	/* Restore the registers */
> +	imx_uart_writel(sport, ubir, UBIR);
> +	imx_uart_writel(sport, ubmr, UBMR);
> +	imx_uart_writel(sport, uts, IMX21_UTS);
> +}
> +
>  /* called with port.lock taken and irqs off */
>  static void imx_uart_start_rx(struct uart_port *port)
>  {
> @@ -1398,7 +1431,7 @@ static void imx_uart_disable_dma(struct imx_port *sport)
>  static int imx_uart_startup(struct uart_port *port)
>  {
>  	struct imx_port *sport = (struct imx_port *)port;
> -	int retval, i;
> +	int retval;
>  	unsigned long flags;
>  	int dma_is_inited = 0;
>  	u32 ucr1, ucr2, ucr3, ucr4, uts;
> @@ -1430,15 +1463,9 @@ static int imx_uart_startup(struct uart_port *port)
>  		dma_is_inited = 1;
>  
>  	spin_lock_irqsave(&sport->port.lock, flags);
> +
>  	/* Reset fifo's and state machines */
> -	i = 100;
> -
> -	ucr2 = imx_uart_readl(sport, UCR2);
> -	ucr2 &= ~UCR2_SRST;
> -	imx_uart_writel(sport, ucr2, UCR2);
> -
> -	while (!(imx_uart_readl(sport, UCR2) & UCR2_SRST) && (--i > 0))
> -		udelay(1);
> +	imx_uart_soft_reset(sport);
>  
>  	/*
>  	 * Finally, clear and enable interrupts
> @@ -1593,8 +1620,6 @@ static void imx_uart_flush_buffer(struct uart_port *port)
>  {
>  	struct imx_port *sport = (struct imx_port *)port;
>  	struct scatterlist *sgl = &sport->tx_sgl[0];
> -	u32 ucr2;
> -	int i = 100, ubir, ubmr, uts;
>  
>  	if (!sport->dma_chan_tx)
>  		return;
> @@ -1612,32 +1637,8 @@ static void imx_uart_flush_buffer(struct uart_port *port)
>  		sport->dma_is_txing = 0;
>  	}
>  
> -	/*
> -	 * According to the Reference Manual description of the UART SRST bit:
> -	 *
> -	 * "Reset the transmit and receive state machines,
> -	 * all FIFOs and register USR1, USR2, UBIR, UBMR, UBRC, URXD, UTXD
> -	 * and UTS[6-3]".
> -	 *
> -	 * We don't need to restore the old values from USR1, USR2, URXD and
> -	 * UTXD. UBRC is read only, so only save/restore the other three
> -	 * registers.
> -	 */
> -	ubir = imx_uart_readl(sport, UBIR);
> -	ubmr = imx_uart_readl(sport, UBMR);
> -	uts = imx_uart_readl(sport, IMX21_UTS);
> +	imx_uart_soft_reset(sport);
>  
> -	ucr2 = imx_uart_readl(sport, UCR2);
> -	ucr2 &= ~UCR2_SRST;
> -	imx_uart_writel(sport, ucr2, UCR2);
> -
> -	while (!(imx_uart_readl(sport, UCR2) & UCR2_SRST) && (--i > 0))
> -		udelay(1);
> -
> -	/* Restore the registers */
> -	imx_uart_writel(sport, ubir, UBIR);
> -	imx_uart_writel(sport, ubmr, UBMR);
> -	imx_uart_writel(sport, uts, IMX21_UTS);
>  }
>  
>  static void
>