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serial: amba-pl011: Fix RTS handling in RS485 mode #7180

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serial: amba-pl011: Fix RTS handling in RS485 mode #7180

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126 changes: 96 additions & 30 deletions drivers/tty/serial/amba-pl011.c
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Original file line number Diff line number Diff line change
Expand Up @@ -262,6 +262,13 @@ struct pl011_dmatx_data {
bool queued;
};

enum pl011_rs485_tx_state {
OFF,
WAIT_AFTER_RTS,
SEND,
WAIT_AFTER_SEND,
};

/*
* We wrap our port structure around the generic uart_port.
*/
Expand All @@ -275,8 +282,10 @@ struct uart_amba_port {
unsigned int fifosize; /* vendor-specific */
unsigned int fixed_baud; /* vendor-set fixed baud rate */
char type[12];
bool rs485_tx_started;
unsigned int rs485_tx_drain_interval; /* usecs */
ktime_t rs485_tx_drain_interval; /* nano */
enum pl011_rs485_tx_state rs485_tx_state;
struct hrtimer trigger_start_tx;
struct hrtimer trigger_stop_tx;
#ifdef CONFIG_DMA_ENGINE
/* DMA stuff */
unsigned int dmacr; /* dma control reg */
Expand Down Expand Up @@ -1281,30 +1290,31 @@ static inline bool pl011_dma_rx_running(struct uart_amba_port *uap)

static void pl011_rs485_tx_stop(struct uart_amba_port *uap)
{
/*
* To be on the safe side only time out after twice as many iterations
* as fifo size.
*/
const int MAX_TX_DRAIN_ITERS = uap->port.fifosize * 2;
struct uart_port *port = &uap->port;
int i = 0;
u32 cr;

/* Wait until hardware tx queue is empty */
while (!pl011_tx_empty(port)) {
if (i > MAX_TX_DRAIN_ITERS) {
dev_warn(port->dev,
"timeout while draining hardware tx queue\n");
break;
}
if (uap->rs485_tx_state == SEND)
uap->rs485_tx_state = WAIT_AFTER_SEND;

udelay(uap->rs485_tx_drain_interval);
i++;
if (uap->rs485_tx_state == WAIT_AFTER_SEND) {
/* Schedule hrtimer if tx queue not empty */
if (!pl011_tx_empty(port)) {
hrtimer_start(&uap->trigger_stop_tx,
uap->rs485_tx_drain_interval,
HRTIMER_MODE_REL);
return;
}
if (port->rs485.delay_rts_after_send > 0) {
hrtimer_start(&uap->trigger_stop_tx,
ms_to_ktime(port->rs485.delay_rts_after_send),
HRTIMER_MODE_REL);
return;
}
/* Continue without any delay */
} else if (uap->rs485_tx_state == WAIT_AFTER_RTS) {
hrtimer_try_to_cancel(&uap->trigger_start_tx);
}

if (port->rs485.delay_rts_after_send)
mdelay(port->rs485.delay_rts_after_send);

cr = pl011_read(uap, REG_CR);

if (port->rs485.flags & SER_RS485_RTS_AFTER_SEND)
Expand All @@ -1317,19 +1327,26 @@ static void pl011_rs485_tx_stop(struct uart_amba_port *uap)
cr |= UART011_CR_RXE;
pl011_write(cr, uap, REG_CR);

uap->rs485_tx_started = false;
uap->rs485_tx_state = OFF;
}

static void pl011_stop_tx(struct uart_port *port)
{
struct uart_amba_port *uap =
container_of(port, struct uart_amba_port, port);

if (port->rs485.flags & SER_RS485_ENABLED &&
uap->rs485_tx_state == WAIT_AFTER_RTS) {
pl011_rs485_tx_stop(uap);
return;
}

uap->im &= ~UART011_TXIM;
pl011_write(uap->im, uap, REG_IMSC);
pl011_dma_tx_stop(uap);

if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)
if (port->rs485.flags & SER_RS485_ENABLED &&
uap->rs485_tx_state != OFF)
pl011_rs485_tx_stop(uap);
}

Expand All @@ -1349,10 +1366,19 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap)
struct uart_port *port = &uap->port;
u32 cr;

if (uap->rs485_tx_state == WAIT_AFTER_RTS) {
uap->rs485_tx_state = SEND;
return;
}
if (uap->rs485_tx_state == WAIT_AFTER_SEND) {
hrtimer_try_to_cancel(&uap->trigger_stop_tx);
uap->rs485_tx_state = SEND;
return;
}
/* uap->rs485_tx_state == OFF */
/* Enable transmitter */
cr = pl011_read(uap, REG_CR);
cr |= UART011_CR_TXE;

/* Disable receiver if half-duplex */
if (!(port->rs485.flags & SER_RS485_RX_DURING_TX))
cr &= ~UART011_CR_RXE;
Expand All @@ -1364,10 +1390,14 @@ static void pl011_rs485_tx_start(struct uart_amba_port *uap)

pl011_write(cr, uap, REG_CR);

if (port->rs485.delay_rts_before_send)
mdelay(port->rs485.delay_rts_before_send);

uap->rs485_tx_started = true;
if (port->rs485.delay_rts_before_send > 0) {
uap->rs485_tx_state = WAIT_AFTER_RTS;
hrtimer_start(&uap->trigger_start_tx,
ms_to_ktime(port->rs485.delay_rts_before_send),
HRTIMER_MODE_REL);
} else {
uap->rs485_tx_state = SEND;
}
}

static void pl011_start_tx(struct uart_port *port)
Expand All @@ -1376,13 +1406,44 @@ static void pl011_start_tx(struct uart_port *port)
container_of(port, struct uart_amba_port, port);

if ((uap->port.rs485.flags & SER_RS485_ENABLED) &&
!uap->rs485_tx_started)
uap->rs485_tx_state != SEND) {
pl011_rs485_tx_start(uap);
if (uap->rs485_tx_state == WAIT_AFTER_RTS)
return;
}

if (!pl011_dma_tx_start(uap))
pl011_start_tx_pio(uap);
}

static enum hrtimer_restart pl011_trigger_start_tx(struct hrtimer *t)
{
struct uart_amba_port *uap =
container_of(t, struct uart_amba_port, trigger_start_tx);
unsigned long flags;

uart_port_lock_irqsave(&uap->port, &flags);
if (uap->rs485_tx_state == WAIT_AFTER_RTS)
pl011_start_tx(&uap->port);
uart_port_unlock_irqrestore(&uap->port, flags);

return HRTIMER_NORESTART;
}

static enum hrtimer_restart pl011_trigger_stop_tx(struct hrtimer *t)
{
struct uart_amba_port *uap =
container_of(t, struct uart_amba_port, trigger_stop_tx);
unsigned long flags;

uart_port_lock_irqsave(&uap->port, &flags);
if (uap->rs485_tx_state == WAIT_AFTER_SEND)
pl011_rs485_tx_stop(uap);
uart_port_unlock_irqrestore(&uap->port, flags);

return HRTIMER_NORESTART;
}

static void pl011_stop_rx(struct uart_port *port)
{
struct uart_amba_port *uap =
Expand Down Expand Up @@ -1979,7 +2040,7 @@ static void pl011_shutdown(struct uart_port *port)

pl011_dma_shutdown(uap);

if ((port->rs485.flags & SER_RS485_ENABLED) && uap->rs485_tx_started)
if ((port->rs485.flags & SER_RS485_ENABLED && uap->rs485_tx_state != OFF))
pl011_rs485_tx_stop(uap);

free_irq(uap->port.irq, uap);
Expand Down Expand Up @@ -2124,7 +2185,7 @@ pl011_set_termios(struct uart_port *port, struct ktermios *termios,
* with the given baud rate. We use this as the poll interval when we
* wait for the tx queue to empty.
*/
uap->rs485_tx_drain_interval = DIV_ROUND_UP(bits * 1000 * 1000, baud);
uap->rs485_tx_drain_interval = ns_to_ktime(DIV_ROUND_UP(bits * NSEC_PER_SEC, baud));

pl011_setup_status_masks(port, termios);

Expand Down Expand Up @@ -2838,6 +2899,11 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
}
}

hrtimer_init(&uap->trigger_start_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
hrtimer_init(&uap->trigger_stop_tx, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
uap->trigger_start_tx.function = pl011_trigger_start_tx;
uap->trigger_stop_tx.function = pl011_trigger_stop_tx;

ret = pl011_setup_port(&dev->dev, uap, &dev->res, portnr);
if (ret)
return ret;
Expand Down