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Message-Id: <20200412180923.30774-3-mani@kernel.org>
Date: Sun, 12 Apr 2020 23:39:23 +0530
From: mani@...nel.org
To: gregkh@...uxfoundation.org, robh+dt@...nel.org,
mcoquelin.stm32@...il.com, alexandre.torgue@...com
Cc: linux-serial@...r.kernel.org, devicetree@...r.kernel.org,
linux-stm32@...md-mailman.stormreply.com,
linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
Manivannan Sadhasivam <mani@...nel.org>
Subject: [PATCH 2/2] tty: serial: Add software flow control support for STM32 USART
From: Manivannan Sadhasivam <mani@...nel.org>
Add software flow control support for STM32 USART controller. This could
be useful when the hardware RTS/CTS pins are not available in the
design.
Signed-off-by: Manivannan Sadhasivam <mani@...nel.org>
---
drivers/tty/serial/stm32-usart.c | 143 +++++++++++++++++++++++++++++--
drivers/tty/serial/stm32-usart.h | 4 +
2 files changed, 141 insertions(+), 6 deletions(-)
diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index 5e93e8d40f59..f8adc108ae19 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -19,6 +19,7 @@
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/of.h>
+#include <linux/of_gpio.h>
#include <linux/of_platform.h>
#include <linux/pinctrl/consumer.h>
#include <linux/platform_device.h>
@@ -94,6 +95,20 @@ static void stm32_config_reg_rs485(u32 *cr1, u32 *cr3, u32 delay_ADE,
*cr1 |= rs485_deat_dedt;
}
+static irqreturn_t stm32_cts_handler(int irq, void *dev_id)
+{
+ struct stm32_port *stm32port = (struct stm32_port *)dev_id;
+ struct uart_port *port = &stm32port->port;
+
+ spin_lock(&port->lock);
+ if (gpio_is_valid(stm32port->cts_gpio) && stm32port->ms_enabled)
+ uart_handle_cts_change(port,
+ !gpio_get_value(stm32port->cts_gpio));
+ spin_unlock(&port->lock);
+
+ return IRQ_HANDLED;
+}
+
static int stm32_config_rs485(struct uart_port *port,
struct serial_rs485 *rs485conf)
{
@@ -506,16 +521,39 @@ static void stm32_set_mctrl(struct uart_port *port, unsigned int mctrl)
struct stm32_port *stm32_port = to_stm32_port(port);
struct stm32_usart_offsets *ofs = &stm32_port->info->ofs;
- if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
- stm32_set_bits(port, ofs->cr3, USART_CR3_RTSE);
- else
- stm32_clr_bits(port, ofs->cr3, USART_CR3_RTSE);
+ if (stm32_port->hw_flow_control) {
+ if ((mctrl & TIOCM_RTS) && (port->status & UPSTAT_AUTORTS))
+ stm32_set_bits(port, ofs->cr3, USART_CR3_RTSE);
+ else
+ stm32_clr_bits(port, ofs->cr3, USART_CR3_RTSE);
+ } else if (stm32_port->sw_flow_control) {
+ if ((mctrl & TIOCM_RTS))
+ gpio_set_value(stm32_port->rts_gpio, 0);
+ else
+ gpio_set_value(stm32_port->rts_gpio, 1);
+ }
}
+/* This routine is used to get signals of: DCD, DSR, RI, and CTS */
static unsigned int stm32_get_mctrl(struct uart_port *port)
{
- /* This routine is used to get signals of: DCD, DSR, RI, and CTS */
+ struct stm32_port *stm32_port = to_stm32_port(port);
+
+ if (!stm32_port->ms_enabled)
+ goto cts_asserted;
+
+ if (stm32_port->sw_flow_control) {
+ if (!gpio_get_value(stm32_port->cts_gpio))
+ goto cts_asserted;
+ else
+ goto cts_deasserted;
+ }
+
+cts_asserted:
return TIOCM_CAR | TIOCM_DSR | TIOCM_CTS;
+
+cts_deasserted:
+ return TIOCM_CAR | TIOCM_DSR;
}
/* Transmit stop */
@@ -582,6 +620,28 @@ static void stm32_break_ctl(struct uart_port *port, int break_state)
{
}
+static void stm32_enable_ms(struct uart_port *port)
+{
+ struct stm32_port *stm32_port = to_stm32_port(port);
+
+ if (!stm32_port->sw_flow_control)
+ return;
+
+ stm32_port->ms_enabled = true;
+ enable_irq(gpio_to_irq(stm32_port->cts_gpio));
+}
+
+static void stm32_disable_ms(struct uart_port *port)
+{
+ struct stm32_port *stm32_port = to_stm32_port(port);
+
+ if (!stm32_port->sw_flow_control)
+ return;
+
+ stm32_port->ms_enabled = false;
+ disable_irq(gpio_to_irq(stm32_port->cts_gpio));
+}
+
static int stm32_startup(struct uart_port *port)
{
struct stm32_port *stm32_port = to_stm32_port(port);
@@ -615,6 +675,19 @@ static int stm32_startup(struct uart_port *port)
val |= USART_CR1_FIFOEN;
stm32_set_bits(port, ofs->cr1, val);
+ stm32_port->ms_enabled = false;
+ if (stm32_port->sw_flow_control) {
+ irq_modify_status(gpio_to_irq(stm32_port->cts_gpio),
+ IRQ_NOREQUEST, IRQ_NOAUTOEN);
+ ret = request_irq(gpio_to_irq(stm32_port->cts_gpio),
+ stm32_cts_handler, IRQF_TRIGGER_FALLING |
+ IRQF_TRIGGER_RISING, "stm32_cts_irq", stm32_port);
+ if (ret != 0) {
+ dev_err(port->dev, "request gpio irq fail\n");
+ return ret;
+ }
+ }
+
return 0;
}
@@ -642,6 +715,14 @@ static void stm32_shutdown(struct uart_port *port)
stm32_clr_bits(port, ofs->cr1, val);
free_irq(port->irq, port);
+
+ if (stm32_port->ms_enabled)
+ stm32_disable_ms(port);
+
+ if (stm32_port->sw_flow_control) {
+ gpio_set_value(stm32_port->rts_gpio, 1);
+ free_irq(gpio_to_irq(stm32_port->cts_gpio), stm32_port);
+ }
}
static unsigned int stm32_get_databits(struct ktermios *termios)
@@ -812,6 +893,14 @@ static void stm32_set_termios(struct uart_port *port, struct ktermios *termios,
if ((termios->c_cflag & CREAD) == 0)
port->ignore_status_mask |= USART_SR_DUMMY_RX;
+ if (UART_ENABLE_MS(port, termios->c_cflag)) {
+ if (!stm32_port->ms_enabled)
+ stm32_enable_ms(port);
+ } else {
+ if (stm32_port->ms_enabled)
+ stm32_disable_ms(port);
+ }
+
if (stm32_port->rx_ch)
cr3 |= USART_CR3_DMAR;
@@ -898,6 +987,7 @@ static const struct uart_ops stm32_uart_ops = {
.throttle = stm32_throttle,
.unthrottle = stm32_unthrottle,
.stop_rx = stm32_stop_rx,
+ .enable_ms = stm32_enable_ms,
.break_ctl = stm32_break_ctl,
.startup = stm32_startup,
.shutdown = stm32_shutdown,
@@ -970,7 +1060,7 @@ static int stm32_init_port(struct stm32_port *stm32port,
static struct stm32_port *stm32_of_get_stm32_port(struct platform_device *pdev)
{
struct device_node *np = pdev->dev.of_node;
- int id;
+ int id, ret;
if (!np)
return NULL;
@@ -990,6 +1080,47 @@ static struct stm32_port *stm32_of_get_stm32_port(struct platform_device *pdev)
stm32_ports[id].cr1_irq = USART_CR1_RXNEIE;
stm32_ports[id].cr3_irq = 0;
stm32_ports[id].last_res = RX_BUF_L;
+
+ stm32_ports[id].sw_flow_control = of_property_read_bool(np,
+ "st,sw-flow-ctrl");
+ if (stm32_ports[id].sw_flow_control) {
+ if (of_find_property(np, "cts-gpios", NULL))
+ stm32_ports[id].cts_gpio =
+ of_get_named_gpio(np, "cts-gpios", 0);
+ else
+ stm32_ports[id].cts_gpio = -1;
+
+ if (of_find_property(np, "rts-gpios", NULL))
+ stm32_ports[id].rts_gpio =
+ of_get_named_gpio(np, "rts-gpios", 0);
+ else
+ stm32_ports[id].rts_gpio = -1;
+
+ if ((!gpio_is_valid(stm32_ports[id].cts_gpio)) ||
+ (!gpio_is_valid(stm32_ports[id].rts_gpio))) {
+ dev_err(&pdev->dev,
+ "SW flow control must have cts and rts gpio");
+ return NULL;
+ }
+
+ ret = devm_gpio_request(&pdev->dev, stm32_ports[id].cts_gpio,
+ "st-cts-gpio");
+ if (ret) {
+ dev_err(&pdev->dev, "Unable request cts gpio");
+ return NULL;
+ }
+
+ gpio_direction_input(stm32_ports[id].cts_gpio);
+ ret = devm_gpio_request(&pdev->dev, stm32_ports[id].rts_gpio,
+ "st-rts-gpio");
+ if (ret) {
+ dev_err(&pdev->dev, "Unable request rts gpio");
+ return NULL;
+ }
+
+ gpio_direction_output(stm32_ports[id].rts_gpio, 1);
+ }
+
return &stm32_ports[id];
}
diff --git a/drivers/tty/serial/stm32-usart.h b/drivers/tty/serial/stm32-usart.h
index a175c1094dc8..87b30f514e15 100644
--- a/drivers/tty/serial/stm32-usart.h
+++ b/drivers/tty/serial/stm32-usart.h
@@ -274,6 +274,10 @@ struct stm32_port {
bool fifoen;
int wakeirq;
int rdr_mask; /* receive data register mask */
+ bool sw_flow_control;
+ unsigned int cts_gpio;
+ unsigned int rts_gpio;
+ bool ms_enabled;
};
static struct stm32_port stm32_ports[STM32_MAX_PORTS];
--
2.17.1
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