[PATCH] serial: zynq: Change fifor behavior in debug mode

[Michal Simek]

pá 25. 3. 2022 v 11:50 odesílatel Michal Simek <michal.simek at xilinx.com> napsal:
>
> Serial IP has output buffer which status is indicated by two bits. If fifo
> if empty or full. Default configuration is that chars are pushed to fifo
> till it is full. Time to time it is visible that chars are scambled and
> logs are not visible. Not sure what it is exactly happening but all the
> time it helps to change driver behavior to write only one char at a time.
> That's why enable this mode when debug uart is enabled not to see scrambled
> chars in debug by default.
>
> Signed-off-by: Michal Simek <michal.simek at xilinx.com>
> ---
>
>  drivers/serial/serial_zynq.c | 10 ++++++++--
>  1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/serial/serial_zynq.c b/drivers/serial/serial_zynq.c
> index fd999368ab70..6bb003dc1558 100644
> --- a/drivers/serial/serial_zynq.c
> +++ b/drivers/serial/serial_zynq.c
> @@ -21,6 +21,7 @@
>
>  #define ZYNQ_UART_SR_TXACTIVE  BIT(11) /* TX active */
>  #define ZYNQ_UART_SR_TXFULL    BIT(4) /* TX FIFO full */
> +#define ZYNQ_UART_SR_TXEMPTY   BIT(3) /* TX FIFO empty */
>  #define ZYNQ_UART_SR_RXEMPTY   BIT(1) /* RX FIFO empty */
>
>  #define ZYNQ_UART_CR_TX_EN     BIT(4) /* TX enabled */
> @@ -107,8 +108,13 @@ static void _uart_zynq_serial_init(struct uart_zynq *regs)
>
>  static int _uart_zynq_serial_putc(struct uart_zynq *regs, const char c)
>  {
> -       if (readl(&regs->channel_sts) & ZYNQ_UART_SR_TXFULL)
> -               return -EAGAIN;
> +       if (CONFIG_IS_ENABLED(DEBUG_UART_ZYNQ)) {
> +               if (!(readl(&regs->channel_sts) & ZYNQ_UART_SR_TXEMPTY))
> +                       return -EAGAIN;
> +       } else {
> +               if (readl(&regs->channel_sts) & ZYNQ_UART_SR_TXFULL)
> +                       return -EAGAIN;
> +       }
>
>         writel(c, &regs->tx_rx_fifo);
>
> --
> 2.35.1
>

Applied with subject s/fifor/fifo/ fixed
M


-- 
Michal Simek, Ing. (M.Eng), OpenPGP -> KeyID: FE3D1F91
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel - Xilinx Microblaze
Maintainer of Linux kernel - Xilinx Zynq ARM and ZynqMP ARM64 SoCs
U-Boot custodian - Xilinx Microblaze/Zynq/ZynqMP/Versal SoCs