linux-kernel - Re: [PATCH v1 2/3] serial: liteuart: separate RX loop from poll timer

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Message-ID: <CACPK8XdGpGUispRcfgaVyE=18Wwg8GFHH7QJ6bcQLA5XDikSiQ@mail.gmail.com>
Date:   Thu, 10 Nov 2022 01:09:59 +0000
From:   Joel Stanley <joel@....id.au>
To:     Gabriel Somlo <gsomlo@...il.com>
Cc:     linux-kernel@...r.kernel.org, linux-serial@...r.kernel.org,
        gregkh@...uxfoundation.org, jirislaby@...nel.org,
        kgugala@...micro.com, mholenko@...micro.com,
        david.abdurachmanov@...ive.com, florent@...oy-digital.fr
Subject: Re: [PATCH v1 2/3] serial: liteuart: separate RX loop from poll timer

On Mon, 7 Nov 2022 at 17:15, Gabriel Somlo <gsomlo@...il.com> wrote:
>
> Move the character-receive (RX) loop to its own dedicated function,
> and (for now) call that from the poll timer, liteuart_timer().
>
> This is in preparation for adding IRQ support to the receive path.
>
> Signed-off-by: Gabriel Somlo <gsomlo@...il.com>
> ---
>  drivers/tty/serial/liteuart.c | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/tty/serial/liteuart.c b/drivers/tty/serial/liteuart.c
> index 4b9cca249828..90a29ed79bff 100644
> --- a/drivers/tty/serial/liteuart.c
> +++ b/drivers/tty/serial/liteuart.c
> @@ -69,29 +69,34 @@ static struct uart_driver liteuart_driver = {
>  #endif
>  };
>
> -static void liteuart_timer(struct timer_list *t)
> +static void liteuart_rx_chars(struct uart_port *port)
>  {
> -       struct liteuart_port *uart = from_timer(uart, t, timer);
> -       struct uart_port *port = &uart->port;
>         unsigned char __iomem *membase = port->membase;
> -       unsigned int flg = TTY_NORMAL;
> -       int ch;
> -       unsigned long status;
> +       unsigned int status;
> +       unsigned char ch;

u32, u8, void __iomem * would be better kernel types to use here.

You've also changed ch from a signed 32 to an unsigned 8.

>
>         while ((status = !litex_read8(membase + OFF_RXEMPTY)) == 1) {
>                 ch = litex_read8(membase + OFF_RXTX);
>                 port->icount.rx++;
>
>                 /* necessary for RXEMPTY to refresh its value */
> -               litex_write8(membase + OFF_EV_PENDING, EV_TX | EV_RX);
> +               litex_write8(membase + OFF_EV_PENDING, EV_RX);

You're no longer clearing EV_TX, but don't mention why (I understand
why with the context of the other changes, so perhaps add something to
this commit message).


>
>                 /* no overflow bits in status */
>                 if (!(uart_handle_sysrq_char(port, ch)))
> -                       uart_insert_char(port, status, 0, ch, flg);
> -
> -               tty_flip_buffer_push(&port->state->port);
> +                       uart_insert_char(port, status, 0, ch, TTY_NORMAL);
>         }
>
> +       tty_flip_buffer_push(&port->state->port);
> +}
> +
> +static void liteuart_timer(struct timer_list *t)
> +{
> +       struct liteuart_port *uart = from_timer(uart, t, timer);
> +       struct uart_port *port = &uart->port;
> +
> +       liteuart_rx_chars(port);
> +
>         mod_timer(&uart->timer, jiffies + uart_poll_timeout(port));
>  }
>
> --
> 2.37.3
>