This adds support for delay_rts_before_send and delay_rts_after_send
using two timers. This change is in the field already for a few
customers on older kernel versions.
Signed-off-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx>
---
drivers/tty/serial/imx.c | 155 ++++++++++++++++++++++++++++++---------
1 file changed, 119 insertions(+), 36 deletions(-)
diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index dff75dc94731..246a1fd409d4 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -192,6 +192,13 @@ struct imx_uart_data {
enum imx_uart_type devtype;
};
+enum imx_tx_state {
+ OFF,
+ WAIT_AFTER_RTS,
+ SEND,
+ WAIT_AFTER_SEND,
+};
+
struct imx_port {
struct uart_port port;
struct timer_list timer;
@@ -226,6 +233,11 @@ struct imx_port {
unsigned int dma_tx_nents;
unsigned int saved_reg[10];
bool context_saved;
+
+ enum imx_tx_state tx_state;
+ unsigned long tx_state_next_change;
+ struct timer_list trigger_start_tx;
+ struct timer_list trigger_stop_tx;
};
struct imx_port_ucrs {
@@ -432,7 +444,10 @@ static void imx_uart_start_rx(struct uart_port *port)
static void imx_uart_stop_tx(struct uart_port *port)
{
struct imx_port *sport = (struct imx_port *)port;
- u32 ucr1;
+ u32 ucr1, ucr4, usr2;
+
+ if (sport->tx_state == OFF)
+ return;
/*
* We are maybe in the SMP context, so if the DMA TX thread is running
@@ -444,21 +459,46 @@ static void imx_uart_stop_tx(struct uart_port *port)
ucr1 = imx_uart_readl(sport, UCR1);
imx_uart_writel(sport, ucr1 & ~UCR1_TXMPTYEN, UCR1);
- /* in rs485 mode disable transmitter if shifter is empty */
- if (port->rs485.flags & SER_RS485_ENABLED &&
- imx_uart_readl(sport, USR2) & USR2_TXDC) {
- u32 ucr2 = imx_uart_readl(sport, UCR2), ucr4;
- if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
- imx_uart_rts_active(sport, &ucr2);
- else
- imx_uart_rts_inactive(sport, &ucr2);
- imx_uart_writel(sport, ucr2, UCR2);
+ usr2 = imx_uart_readl(sport, USR2);
+ if (!(usr2 & USR2_TXDC)) {
+ /* The shifter is still busy, so retry once TC triggers */
+ return;
+ }
- imx_uart_start_rx(port);
+ ucr4 = imx_uart_readl(sport, UCR4);
+ ucr4 &= ~UCR4_TCEN;
+ imx_uart_writel(sport, ucr4, UCR4);
- ucr4 = imx_uart_readl(sport, UCR4);
- ucr4 &= ~UCR4_TCEN;
- imx_uart_writel(sport, ucr4, UCR4);
+ /* in rs485 mode disable transmitter */
+ if (port->rs485.flags & SER_RS485_ENABLED) {
+ if (sport->tx_state == SEND) {
+ sport->tx_state = WAIT_AFTER_SEND;
+ sport->tx_state_next_change =
+ jiffies + DIV_ROUND_UP(port->rs485.delay_rts_after_send * HZ, 1000);
+ }
+
+ if (sport->tx_state == WAIT_AFTER_RTS ||
+ (sport->tx_state == WAIT_AFTER_SEND &&
+ time_after_eq(jiffies, sport->tx_state_next_change))) {
+ u32 ucr2;
+
+ del_timer(&sport->trigger_start_tx);
+
+ ucr2 = imx_uart_readl(sport, UCR2);
+ if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
+ imx_uart_rts_active(sport, &ucr2);
+ else
+ imx_uart_rts_inactive(sport, &ucr2);
+ writel(ucr2, port->membase + UCR2);
+
+ imx_uart_start_rx(port);
+
+ sport->tx_state = OFF;
+ } else if (sport->tx_state == WAIT_AFTER_SEND) {
+ mod_timer(&sport->trigger_stop_tx, sport->tx_state_next_change);
+ }
+ } else {
+ sport->tx_state = OFF;
}
}
@@ -656,28 +696,53 @@ static void imx_uart_start_tx(struct uart_port *port)
if (!sport->port.x_char && uart_circ_empty(&port->state->xmit))
return;
+ /*
+ * We cannot simply do nothing here if sport->tx_state == SEND already
+ * because UCR1_TXMPTYEN might already have been cleared in
+ * imx_uart_stop_tx(), but tx_state is still SEND.
+ */
+
if (port->rs485.flags & SER_RS485_ENABLED) {
- u32 ucr2;
+ if (sport->tx_state == OFF) {
+ u32 ucr2 = imx_uart_readl(sport, UCR2);
+ if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
+ imx_uart_rts_active(sport, &ucr2);
+ else
+ imx_uart_rts_inactive(sport, &ucr2);
+ imx_uart_writel(sport, ucr2, UCR2);
- ucr2 = imx_uart_readl(sport, UCR2);
- if (port->rs485.flags & SER_RS485_RTS_ON_SEND)
- imx_uart_rts_active(sport, &ucr2);
- else
- imx_uart_rts_inactive(sport, &ucr2);
- imx_uart_writel(sport, ucr2, UCR2);
+ if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
+ imx_uart_stop_rx(port);
- if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
- imx_uart_stop_rx(port);
+ sport->tx_state = WAIT_AFTER_RTS;
+ sport->tx_state_next_change =
+ jiffies + DIV_ROUND_UP(port->rs485.delay_rts_before_send * HZ, 1000);
+ }
- /*
- * Enable transmitter and shifter empty irq only if DMA is off.
- * In the DMA case this is done in the tx-callback.
- */
- if (!sport->dma_is_enabled) {
- u32 ucr4 = imx_uart_readl(sport, UCR4);
- ucr4 |= UCR4_TCEN;
- imx_uart_writel(sport, ucr4, UCR4);
+ if (sport->tx_state == WAIT_AFTER_SEND ||
+ (sport->tx_state == WAIT_AFTER_RTS &&
+ time_after_eq(jiffies, sport->tx_state_next_change))) {
+
+ del_timer(&sport->trigger_stop_tx);
+ /*
+ * Enable transmitter and shifter empty irq only if DMA
+ * is off. In the DMA case this is done in the
+ * tx-callback.
+ */
+ if (!sport->dma_is_enabled) {
+ u32 ucr4 = imx_uart_readl(sport, UCR4);
+ ucr4 |= UCR4_TCEN;
+ imx_uart_writel(sport, ucr4, UCR4);
+ }
+
+ sport->tx_state = SEND;
+
+ } else if (sport->tx_state == WAIT_AFTER_RTS) {
+ mod_timer(&sport->trigger_start_tx, sport->tx_state_next_change);
+ return;
}
+ } else {
+ sport->tx_state = SEND;
}
if (!sport->dma_is_enabled) {
@@ -1584,7 +1649,6 @@ imx_uart_set_termios(struct uart_port *port, struct ktermios *termios,
imx_uart_rts_inactive(sport, &ucr2);
}
-
if (termios->c_cflag & CSTOPB)
ucr2 |= UCR2_STPB;
if (termios->c_cflag & PARENB) {
@@ -1828,10 +1892,6 @@ static int imx_uart_rs485_config(struct uart_port *port,
struct imx_port *sport = (struct imx_port *)port;
u32 ucr2;
- /* unimplemented */
- rs485conf->delay_rts_before_send = 0;
- rs485conf->delay_rts_after_send = 0;
-
/* RTS is required to control the transmitter */
if (!sport->have_rtscts && !sport->have_rtsgpio)
rs485conf->flags &= ~SER_RS485_ENABLED;
@@ -2188,6 +2248,26 @@ static void imx_uart_probe_pdata(struct imx_port *sport,
sport->have_rtscts = 1;
}
+static void imx_trigger_start_tx(struct timer_list *t)
+{
+ struct imx_port *sport = from_timer(sport, t, trigger_start_tx);
+ unsigned long flags;
+
+ spin_lock_irqsave(&sport->port.lock, flags);
+ imx_uart_start_tx(&sport->port);
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+}
+
+static void imx_trigger_stop_tx(struct timer_list *t)
+{
+ struct imx_port *sport = from_timer(sport, t, trigger_stop_tx);
+ unsigned long flags;
+
+ spin_lock_irqsave(&sport->port.lock, flags);
+ imx_uart_stop_tx(&sport->port);
+ spin_unlock_irqrestore(&sport->port.lock, flags);
+}
+
static int imx_uart_probe(struct platform_device *pdev)
{
struct imx_port *sport;
@@ -2327,6 +2407,9 @@ static int imx_uart_probe(struct platform_device *pdev)
clk_disable_unprepare(sport->clk_ipg);
+ timer_setup(&sport->trigger_start_tx, imx_trigger_start_tx, 0);
+ timer_setup(&sport->trigger_stop_tx, imx_trigger_stop_tx, 0);
+
/*
* Allocate the IRQ(s) i.MX1 has three interrupts whereas later
* chips only have one interrupt.
--
2.20.1
