linux-kernel - RE: [EXT] [PATCH v1 3/3] tty: serial: lpuart: Add RS485 support for 32-bit uart flavour

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Message-ID: <VI1PR0402MB36007F03DB38FDA44FED3332FF6D0@VI1PR0402MB3600.eurprd04.prod.outlook.com>
Date:   Thu, 17 Oct 2019 05:14:15 +0000
From:   Andy Duan <fugang.duan@....com>
To:     Philippe Schenker <philippe.schenker@...adex.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>
CC:     Max Krummenacher <max.krummenacher@...adex.com>,
        Jiri Slaby <jslaby@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Stefan Agner <stefan@...er.ch>,
        dl-linux-imx <linux-imx@....com>,
        Andrey Smirnov <andrew.smirnov@...il.com>
Subject: RE: [EXT] [PATCH v1 3/3] tty: serial: lpuart: Add RS485 support for
 32-bit uart flavour

From: Philippe Schenker <philippe.schenker@...adex.com> Sent: Wednesday, October 16, 2019 11:19 PM
> This commits adds RS485 support for LPUART hardware that uses 32-bit
> registers. These are typically found in i.MX8 processors.
> 
> Signed-off-by: Philippe Schenker <philippe.schenker@...adex.com>

Reviewed-by: Fugang Duan <fugang.duan@....com>
> 
> ---
> 
>  drivers/tty/serial/fsl_lpuart.c | 65 ++++++++++++++++++++++++++++++++-
>  1 file changed, 63 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/tty/serial/fsl_lpuart.c b/drivers/tty/serial/fsl_lpuart.c index
> 346b4a070ce9..22df5f8f48b6 100644
> --- a/drivers/tty/serial/fsl_lpuart.c
> +++ b/drivers/tty/serial/fsl_lpuart.c
> @@ -1280,6 +1280,57 @@ static int lpuart_config_rs485(struct uart_port
> *port,
>         return 0;
>  }
> 
> +static int lpuart32_config_rs485(struct uart_port *port,
> +                       struct serial_rs485 *rs485) {
> +       struct lpuart_port *sport = container_of(port,
> +                       struct lpuart_port, port);
> +
> +       unsigned long modem = lpuart32_read(&sport->port, UARTMODIR)
> +                               & ~(UARTMODEM_TXRTSPOL |
> UARTMODEM_TXRTSE);
> +       lpuart32_write(&sport->port, modem, UARTMODIR);
> +
> +       /* clear unsupported configurations */
> +       rs485->delay_rts_before_send = 0;
> +       rs485->delay_rts_after_send = 0;
> +       rs485->flags &= ~SER_RS485_RX_DURING_TX;
> +
> +       if (rs485->flags & SER_RS485_ENABLED) {
> +               /* Enable auto RS-485 RTS mode */
> +               modem |= UARTMODEM_TXRTSE;
> +
> +               /*
> +                * RTS needs to be logic HIGH either during transer _or_
> after
> +                * transfer, other variants are not supported by the
> hardware.
> +                */
> +
> +               if (!(rs485->flags & (SER_RS485_RTS_ON_SEND |
> +                               SER_RS485_RTS_AFTER_SEND)))
> +                       rs485->flags |= SER_RS485_RTS_ON_SEND;
> +
> +               if (rs485->flags & SER_RS485_RTS_ON_SEND &&
> +                               rs485->flags &
> SER_RS485_RTS_AFTER_SEND)
> +                       rs485->flags &=
> ~SER_RS485_RTS_AFTER_SEND;
> +
> +               /*
> +                * The hardware defaults to RTS logic HIGH while
> transfer.
> +                * Switch polarity in case RTS shall be logic HIGH
> +                * after transfer.
> +                * Note: UART is assumed to be active high.
> +                */
> +               if (rs485->flags & SER_RS485_RTS_ON_SEND)
> +                       modem &= ~UARTMODEM_TXRTSPOL;
> +               else if (rs485->flags & SER_RS485_RTS_AFTER_SEND)
> +                       modem |= UARTMODEM_TXRTSPOL;
> +       }
> +
> +       /* Store the new configuration */
> +       sport->port.rs485 = *rs485;
> +
> +       lpuart32_write(&sport->port, modem, UARTMODIR);
> +       return 0;
> +}
> +
>  static unsigned int lpuart_get_mctrl(struct uart_port *port)  {
>         unsigned int temp = 0;
> @@ -1878,6 +1929,13 @@ lpuart32_set_termios(struct uart_port *port,
> struct ktermios *termios,
>                 ctrl |= UARTCTRL_M;
>         }
> 
> +       /*
> +        * When auto RS-485 RTS mode is enabled,
> +        * hardware flow control need to be disabled.
> +        */
> +       if (sport->port.rs485.flags & SER_RS485_ENABLED)
> +               termios->c_cflag &= ~CRTSCTS;
> +
>         if (termios->c_cflag & CRTSCTS) {
>                 modem |= (UARTMODIR_RXRTSE |
> UARTMODIR_TXCTSE);
>         } else {
> @@ -2405,7 +2463,10 @@ static int lpuart_probe(struct platform_device
> *pdev)
>                 sport->port.ops = &lpuart_pops;
>         sport->port.flags = UPF_BOOT_AUTOCONF;
> 
> -       sport->port.rs485_config = lpuart_config_rs485;
> +       if (lpuart_is_32(sport))
> +               sport->port.rs485_config = lpuart32_config_rs485;
> +       else
> +               sport->port.rs485_config = lpuart_config_rs485;
> 
>         sport->ipg_clk = devm_clk_get(&pdev->dev, "ipg");
>         if (IS_ERR(sport->ipg_clk)) {
> @@ -2459,7 +2520,7 @@ static int lpuart_probe(struct platform_device
> *pdev)
>             sport->port.rs485.delay_rts_after_send)
>                 dev_err(&pdev->dev, "driver doesn't support RTS
> delays\n");
> 
> -       lpuart_config_rs485(&sport->port, &sport->port.rs485);
> +       sport->port.rs485_config(&sport->port, &sport->port.rs485);
> 
>         sport->dma_tx_chan =
> dma_request_slave_channel(sport->port.dev, "tx");
>         if (!sport->dma_tx_chan)
> --
> 2.23.0