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@xxxxxxxxx>
> ---
> 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
>
