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Subject[PATCH 1/4] serial: 8250_dw: add em485 support
Date
Need to use rs485 transceiver so let's use existing em485 485 emulation
layer on top of 8250.

Add rs485_config callback to port.

Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
---
drivers/tty/serial/8250/8250_dw.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)

diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 6fcdb90f616a..45366e6e5411 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -314,6 +314,36 @@ static void dw8250_set_ldisc(struct uart_port *p, struct ktermios *termios)
serial8250_do_set_ldisc(p, termios);
}

+static int dw8250_rs485_config(struct uart_port *p,
+ struct serial_rs485 *rs485)
+{
+ struct uart_8250_port *up = up_to_u8250p(p);
+
+ /* 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);
+
+ p->rs485 = *rs485;
+
+ /*
+ * Both serial8250_em485_init and serial8250_em485_destroy
+ * are idempotent
+ */
+ if (rs485->flags & SER_RS485_ENABLED) {
+ int ret = serial8250_em485_init(up);
+
+ if (ret) {
+ rs485->flags &= ~SER_RS485_ENABLED;
+ p->rs485.flags &= ~SER_RS485_ENABLED;
+ }
+ return ret;
+ }
+
+ serial8250_em485_destroy(up);
+
+ return 0;
+}
+
/*
* dw8250_fallback_dma_filter will prevent the UART from getting just any free
* channel on platforms that have DMA engines, but don't have any channels
@@ -449,6 +479,7 @@ static int dw8250_probe(struct platform_device *pdev)
p->serial_out = dw8250_serial_out;
p->set_ldisc = dw8250_set_ldisc;
p->set_termios = dw8250_set_termios;
+ p->rs485_config = dw8250_rs485_config;

p->membase = devm_ioremap(dev, regs->start, resource_size(regs));
if (!p->membase)
--
2.17.1
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