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linux-raspberrypi: Control RTS pins for Seeed'd RS-485 implementation #1172

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linux-raspberrypi: Control RTS pins for Seeed'd RS-485 implementation #1172

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66 changes: 66 additions & 0 deletions ...nel/linux/linux-raspberrypi/raspberrypicm4-ioboard/0001-Add-serial-RTS-control-gpio.patch
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Original file line number Diff line number Diff line change
@@ -0,0 +1,66 @@
From ec4e5cc6a5e68eb93b4775eb28626cddd0ff7a89 Mon Sep 17 00:00:00 2001
From: qian <[email protected]>
Date: Fri, 16 Aug 2024 06:03:06 +0000
Subject: [PATCH] Add serial RTS control gpio

---
drivers/tty/serial/serial_core.c | 16 ++++++++++++++++
include/linux/serial_core.h | 1 +
2 files changed, 17 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index 45b721abaa2f..8fa249678f52 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -567,6 +567,10 @@ static int uart_write(struct tty_struct *tty,
}

port = uart_port_lock(state, flags);
+ if(port->rts_gpio)
+ {
+ gpiod_set_value(port->rts_gpio, 1);
+ }
circ = &state->xmit;
if (!circ->buf) {
uart_port_unlock(port, flags);
@@ -587,6 +591,11 @@ static int uart_write(struct tty_struct *tty,
}

__uart_start(tty);
+
+ if(port->rts_gpio)
+ {
+ gpiod_set_value(port->rts_gpio, 0);
+ }
uart_port_unlock(port, flags);
return ret;
}
@@ -2991,6 +3000,13 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
*/
uport->flags &= ~UPF_DEAD;

+ uport->rts_gpio = devm_gpiod_get_optional(uport->dev, "rts",
+ GPIOD_OUT_LOW);
+ if (IS_ERR(uport->rts_gpio)) {
+ ret = PTR_ERR(uport->rts_gpio);
+ uport->rts_gpio = NULL;
+ return dev_err_probe(uport->dev, ret, "Cannot get rts-gpios\n");
+ }
out:
mutex_unlock(&port->mutex);
mutex_unlock(&port_mutex);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index d5b6b1550d59..3ba7bf798bff 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -256,6 +256,7 @@ struct uart_port {
struct serial_rs485 rs485;
const struct serial_rs485 *rs485_supported; /* Supported mask for serial_rs485 */
struct gpio_desc *rs485_term_gpio; /* enable RS485 bus termination */
+ struct gpio_desc *rts_gpio; /* enable RS485 RTS */
struct serial_iso7816 iso7816;
void *private_data; /* generic platform data pointer */
};
--
2.25.1

4 changes: 4 additions & 0 deletions layers/meta-balena-raspberrypi/recipes-kernel/linux/linux-raspberrypi_5.15.bbappend
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Original file line number Diff line number Diff line change
Expand Up @@ -38,6 +38,10 @@ SRC_URI:append:raspberrypi3-unipi-neuron = " \
file://0001-pi3neuron-disable-gccplugins.patch \
"

SRC_URI:append:raspberrypicm4-ioboard = " \
file://0001-Add-serial-RTS-control-gpio.patch \
"

BALENA_CONFIGS:append = " fbtft"
BALENA_CONFIGS[fbtft] = " \
CONFIG_STAGING=y \
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