On Fri, Jun 18, 2021 at 04:51:53PM +0200, Lino Sanfilippo wrote:
> Add basic support for RS485: Provide a callback to configure RS485
> settings. Handle the RS485 specific part in the functions
> pl011_rs485_tx_start() and pl011_rs485_tx_stop() which extend the generic
> start/stop callbacks.
> Beside via IOCTL from userspace RS485 can be enabled by means of the
> device tree property "rs485-enabled-at-boot-time".
>
> Signed-off-by: Lino Sanfilippo <LinoSanfilippo@xxxxxx>
> ---
> This patch applies against Gregs tty-testing branch and was tested on a
> Raspberry Pi CM3.
>
> Changes in V2:
> - clamp RTS delays to 100ms as suggested by Jiri Slaby
> - instead of counting bits "by hand" use the new function tty_get_frame_size()
> (also suggested by Jiri)
> - use the term RS485 consistently in the commit message
> - remove one blank line
>
>
> drivers/tty/serial/amba-pl011.c | 152 +++++++++++++++++++++++++++++++-
> 1 file changed, 150 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> index e14f3378b8a0..92c6b08d56fb 100644
> --- a/drivers/tty/serial/amba-pl011.c
> +++ b/drivers/tty/serial/amba-pl011.c
> @@ -265,6 +265,8 @@ struct uart_amba_port {
> unsigned int old_cr; /* state during shutdown */
> unsigned int fixed_baud; /* vendor-set fixed baud rate */
> char type[12];
> + bool rs485_tx_started;
> + unsigned int rs485_tx_drain_interval; /* usecs */
> #ifdef CONFIG_DMA_ENGINE
> /* DMA stuff */
> bool using_tx_dma;
> @@ -275,6 +277,8 @@ struct uart_amba_port {
> #endif
> };
>
> +static unsigned int pl011_tx_empty(struct uart_port *port);
> +
> static unsigned int pl011_reg_to_offset(const struct uart_amba_port *uap,
> unsigned int reg)
> {
> @@ -1282,6 +1286,34 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)
> #define pl011_dma_flush_buffer NULL
> #endif
>
> +static int pl011_rs485_tx_stop(struct uart_amba_port *uap)
> +{
> + struct uart_port *port = &uap->port;
> + u32 cr;
> +
> + /* Wait until hardware tx queue is empty */
> + while (!pl011_tx_empty(port))
> + udelay(uap->rs485_tx_drain_interval);
No way out if the hardware doesn't ever empty? Shouldn't you have an
"upper bound" on this loop somehow?
> +
> + if (port->rs485.delay_rts_after_send)
> + mdelay(port->rs485.delay_rts_after_send);
> +
> + cr = pl011_read(uap, REG_CR);
> +
> + if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
> + cr &= ~UART011_CR_RTS;
> + else
> + cr |= UART011_CR_RTS;
Blank line here please.
> + /* Disable the transmitter and reenable the transceiver */
> + cr &= ~UART011_CR_TXE;
> + cr |= UART011_CR_RXE;
> + pl011_write(cr, uap, REG_CR);
> +
> + uap->rs485_tx_started = false;
> +
> + return 0;
Why does this function return a value if it can not fail and you do not
check the return value of it?
> +}
> +
> static void pl011_stop_tx(struct uart_port *port)
> {
> struct uart_amba_port *uap =
> @@ -1290,6 +1322,9 @@ static void pl011_stop_tx(struct uart_port *port)
> uap->im &= ~UART011_TXIM;
> pl011_write(uap->im, uap, REG_IMSC);
> pl011_dma_tx_stop(uap);
> +
> + if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)
> + pl011_rs485_tx_stop(uap);
So, no check :(
> }
>
> static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq);
> @@ -1380,6 +1415,31 @@ static bool pl011_tx_char(struct uart_amba_port *uap, unsigned char c,
> return true;
> }
>
> +static void pl011_rs485_tx_start(struct uart_amba_port *uap)
> +{
> + struct uart_port *port = &uap->port;
> + u32 cr;
> +
> + /* Enable transmitter */
> + cr = pl011_read(uap, REG_CR);
> + cr |= UART011_CR_TXE;
Blank line please.
> + /* Disable receiver if half-duplex */
> + if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
> + cr &= ~UART011_CR_RXE;
> +
> + if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
> + cr &= ~UART011_CR_RTS;
> + else
> + cr |= UART011_CR_RTS;
> +
> + pl011_write(cr, uap, REG_CR);
> +
> + if (port->rs485.delay_rts_before_send)
> + mdelay(port->rs485.delay_rts_before_send);
> +
> + uap->rs485_tx_started = true;
> +}
> +
> /* Returns true if tx interrupts have to be (kept) enabled */
> static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq)
> {
> @@ -1397,6 +1457,10 @@ static bool pl011_tx_chars(struct uart_amba_port *uap, bool from_irq)
> return false;
> }
>
> + if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&
> + !uap->rs485_tx_started)
> + pl011_rs485_tx_start(uap);
> +
> /* If we are using DMA mode, try to send some characters. */
> if (pl011_dma_tx_irq(uap))
> return true;
> @@ -1542,6 +1606,9 @@ static void pl011_set_mctrl(struct uart_port *port, unsigned int mctrl)
> container_of(port, struct uart_amba_port, port);
> unsigned int cr;
>
> + if (port->rs485.flags & SER_RS485_ENABLED)
> + mctrl &= ~TIOCM_RTS;
> +
> cr = pl011_read(uap, REG_CR);
>
> #define TIOCMBIT(tiocmbit, uartbit) \
> @@ -1763,7 +1830,17 @@ static int pl011_startup(struct uart_port *port)
>
> /* restore RTS and DTR */
> cr = uap->old_cr & (UART011_CR_RTS | UART011_CR_DTR);
> - cr |= UART01x_CR_UARTEN | UART011_CR_RXE | UART011_CR_TXE;
> + cr |= UART01x_CR_UARTEN | UART011_CR_RXE;
> +
> + if (port->rs485.flags & SER_RS485_ENABLED) {
> + if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
> + cr &= ~UART011_CR_RTS;
> + else
> + cr |= UART011_CR_RTS;
> + } else {
> + cr |= UART011_CR_TXE;
> + }
> +
> pl011_write(cr, uap, REG_CR);
>
> spin_unlock_irq(&uap->port.lock);
> @@ -1864,6 +1941,9 @@ static void pl011_shutdown(struct uart_port *port)
>
> pl011_dma_shutdown(uap);
>
> + if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)
> + pl011_rs485_tx_stop(uap);
> +
> free_irq(uap->port.irq, uap);
>
> pl011_disable_uart(uap);
> @@ -1941,6 +2021,7 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
> unsigned int lcr_h, old_cr;
> unsigned long flags;
> unsigned int baud, quot, clkdiv;
> + unsigned int bits;
>
> if (uap->vendor->oversampling)
> clkdiv = 8;
> @@ -1991,18 +2072,29 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
> if (uap->fifosize > 1)
> lcr_h |= UART01x_LCRH_FEN;
>
> + bits = tty_get_frame_size(termios->c_cflag);
> +
> spin_lock_irqsave(&port->lock, flags);
>
> /*
> * Update the per-port timeout.
> */
> uart_update_timeout(port, termios->c_cflag, baud);
Blank line
> + /*
> + * Calculate the approximated time it takes to transmit one character
> + * with the given baud rate. We use this as the poll interval when we
> + * wait for the tx queue to empty.
> + */
> + uap->rs485_tx_drain_interval = (bits * 1000 * 1000) / baud;
>
> pl011_setup_status_masks(port, termios);
>
> if (UART_ENABLE_MS(port, termios->c_cflag))
> pl011_enable_ms(port);
>
> + if (port->rs485.flags & SER_RS485_ENABLED)
> + termios->c_cflag &= ~CRTSCTS;
> +
> /* first, disable everything */
> old_cr = pl011_read(uap, REG_CR);
> pl011_write(0, uap, REG_CR);
> @@ -2124,6 +2216,40 @@ static int pl011_verify_port(struct uart_port *port, struct serial_struct *ser)
> return ret;
> }
>
> +static int pl011_rs485_config(struct uart_port *port,
> + struct serial_rs485 *rs485)
> +{
> + struct uart_amba_port *uap =
> + container_of(port, struct uart_amba_port, port);
> +
> + /* pick sane settings if the user hasn't */
> + if (!!(rs485->flags & SER_RS485_RTS_ON_SEND) ==
Why the !! in an if statement?
> + !!(rs485->flags & SER_RS485_RTS_AFTER_SEND)) {
Same here, why?
> + rs485->flags |= SER_RS485_RTS_ON_SEND;
> + rs485->flags &= ~SER_RS485_RTS_AFTER_SEND;
> + }
> + /* clamp the delays to [0, 100ms] */
> + rs485->delay_rts_before_send = min(rs485->delay_rts_before_send, 100U);
> + rs485->delay_rts_after_send = min(rs485->delay_rts_after_send, 100U);
> + memset(rs485->padding, 0, sizeof(rs485->padding));
> +
> + if (port->rs485.flags & SER_RS485_ENABLED)
> + pl011_rs485_tx_stop(uap);
> +
> + /* Set new configuration */
> + port->rs485 = *rs485;
Blank line please.
> + /* Make sure auto RTS is disabled */
> + if (port->rs485.flags & SER_RS485_ENABLED) {
> + u32 cr = pl011_read(uap, REG_CR);
> +
> + cr &= ~UART011_CR_RTSEN;
> + pl011_write(cr, uap, REG_CR);
> + port->status &= ~UPSTAT_AUTORTS;
> + }
> +
> + return 0;
> +}
> +
thanks,
greg k-h
