From: Jakub Kicinski <kubakici@xxxxx>
Hardware is capable of inverting RTS signal when working
in RS-485 mode. Expose this functionality to user space.
Relay on a matching combination of standard flags
(SER_RS485_RTS_ON_SEND and SER_RS485_RTS_AFTER_SEND) to
detect when user space is requesting inverted RTS mode.
Signed-off-by: Jakub Kicinski <kubakici@xxxxx>
---
Thank you for prompt review. I changed to dev_err and made the message
more explicit. I also added the current flag setting to the message to
make it more obvious which parameters influence the error. Are these
changes steps in a right direction?
v3: - change to error
- add more information to the message
v2: - print a warning instead of returning -EINVAL to avoid
breaking existing apps
---
drivers/tty/serial/sc16is7xx.c | 34 +++++++++++++++++++++++++---------
1 file changed, 25 insertions(+), 9 deletions(-)
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 36b3c266925d..468354ef7baa 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -829,16 +829,32 @@ static void sc16is7xx_set_termios(struct uart_port *port,
}
static int sc16is7xx_config_rs485(struct uart_port *port,
- struct serial_rs485 *rs485)
+ struct serial_rs485 *rs485)
{
- if (port->rs485.flags & SER_RS485_ENABLED)
- sc16is7xx_port_update(port, SC16IS7XX_EFCR_REG,
- SC16IS7XX_EFCR_AUTO_RS485_BIT,
- SC16IS7XX_EFCR_AUTO_RS485_BIT);
- else
- sc16is7xx_port_update(port, SC16IS7XX_EFCR_REG,
- SC16IS7XX_EFCR_AUTO_RS485_BIT,
- 0);
+ const u32 mask = SC16IS7XX_EFCR_AUTO_RS485_BIT |
+ SC16IS7XX_EFCR_RTS_INVERT_BIT;
+ u32 efcr = 0;
+
+ if (rs485->flags & SER_RS485_ENABLED) {
+ bool rts_during_rx, rts_during_tx;
+
+ rts_during_rx = rs485->flags & SER_RS485_RTS_AFTER_SEND;
+ rts_during_tx = rs485->flags & SER_RS485_RTS_ON_SEND;
+
+ efcr |= SC16IS7XX_EFCR_AUTO_RS485_BIT;
+
+ if (!rts_during_rx && rts_during_tx)
+ /* default */;
+ else if (rts_during_rx && !rts_during_tx)
+ efcr |= SC16IS7XX_EFCR_RTS_INVERT_BIT;
+ else
+ dev_err(port->dev,
+ "unsupported RTS signalling on_send:%d after_send:%d - exactly one of RS485 RTS flags should be set\n",
+ rts_during_tx, rts_during_rx);
+ }
+
+ sc16is7xx_port_update(port, SC16IS7XX_EFCR_REG, mask, efcr);
+
port->rs485 = *rs485;
return 0;
--
2.1.0
--
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