linux-kernel - Re: [PATCH v2] serial: sprd: Add polling IO support

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Message-ID: <CAMz4kuJzYa_4TsvgdWo4nZ9ReroEf9+LCqQh4DD5jO8jfSnf3w@mail.gmail.com>
Date:   Thu, 19 Sep 2019 11:21:07 +0800
From:   Baolin Wang <baolin.wang@...aro.org>
To:     Lanqing Liu <liuhhome@...il.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>, Jiri Slaby <jslaby@...e.com>,
        刘岚清 (Lanqing Liu) 
        <lanqing.liu@...soc.com>, linux-serial@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        Orson Zhai <orsonzhai@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>
Subject: Re: [PATCH v2] serial: sprd: Add polling IO support

Hi,

On Thu, 19 Sep 2019 at 11:10, Lanqing Liu <liuhhome@...il.com> wrote:
>
> In order to access the UART without the interrupts, the kernel uses
> the basic polling methods for IO with the device. With these methods
> implemented, it is now possible to enable kgdb during early boot over serial.
>
> Signed-off-by: Lanqing Liu <liuhhome@...il.com>
> ---
> Change from v1:
>  - Add poll_init() support.

Looks good to me and the KGDB can work well on my board, so feel free
to add my tags:
Reviewed-by: Baolin Wang <baolin.wang@...aro.org>
Tested-by: Baolin Wang <baolin.wang@...aro.org>

> ---
>  drivers/tty/serial/sprd_serial.c | 33 +++++++++++++++++++++++++++++++++
>  1 file changed, 33 insertions(+)
>
> diff --git a/drivers/tty/serial/sprd_serial.c b/drivers/tty/serial/sprd_serial.c
> index 73d71a4..d833160 100644
> --- a/drivers/tty/serial/sprd_serial.c
> +++ b/drivers/tty/serial/sprd_serial.c
> @@ -911,6 +911,34 @@ static void sprd_pm(struct uart_port *port, unsigned int state,
>         }
>  }
>
> +#ifdef CONFIG_CONSOLE_POLL
> +static int sprd_poll_init(struct uart_port *port)
> +{
> +       if (port->state->pm_state != UART_PM_STATE_ON) {
> +               sprd_pm(port, UART_PM_STATE_ON, 0);
> +               port->state->pm_state = UART_PM_STATE_ON;
> +       }
> +
> +       return 0;
> +}
> +
> +static int sprd_poll_get_char(struct uart_port *port)
> +{
> +       while (!(serial_in(port, SPRD_STS1) & SPRD_RX_FIFO_CNT_MASK))
> +               cpu_relax();
> +
> +       return serial_in(port, SPRD_RXD);
> +}
> +
> +static void sprd_poll_put_char(struct uart_port *port, unsigned char ch)
> +{
> +       while (serial_in(port, SPRD_STS1) & SPRD_TX_FIFO_CNT_MASK)
> +               cpu_relax();
> +
> +       serial_out(port, SPRD_TXD, ch);
> +}
> +#endif
> +
>  static const struct uart_ops serial_sprd_ops = {
>         .tx_empty = sprd_tx_empty,
>         .get_mctrl = sprd_get_mctrl,
> @@ -928,6 +956,11 @@ static void sprd_pm(struct uart_port *port, unsigned int state,
>         .config_port = sprd_config_port,
>         .verify_port = sprd_verify_port,
>         .pm = sprd_pm,
> +#ifdef CONFIG_CONSOLE_POLL
> +       .poll_init      = sprd_poll_init,
> +       .poll_get_char  = sprd_poll_get_char,
> +       .poll_put_char  = sprd_poll_put_char,
> +#endif
>  };
>
>  #ifdef CONFIG_SERIAL_SPRD_CONSOLE
> --
> 1.9.1
>


-- 
Baolin Wang
Best Regards