Merge tag 'tty-6.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial driver fixes from Greg KH:
 "Here are a number of small tty and serial driver fixes for 6.1-rc6.
  They all resolve reported problems:

   - kernel doc build problems with the -rc1 serial driver documentation
     update

   - n_gsm reported problems

   - imx serial driver missing callback

   - lots of tiny 8250 driver fixes for reported issues.

  All of these have been in linux-next for over a week with no reported
  problems"

* tag 'tty-6.1-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  docs/driver-api/miscellaneous: Remove kernel-doc of serial_core.c
  serial: 8250: Flush DMA Rx on RLSI
  serial: 8250_lpss: Use 16B DMA burst with Elkhart Lake
  serial: 8250_lpss: Configure DMA also w/o DMA filter
  serial: 8250: Fall back to non-DMA Rx if IIR_RDI occurs
  tty: n_gsm: fix sleep-in-atomic-context bug in gsm_control_send
  Revert "tty: n_gsm: replace kicktimer with delayed_work"
  Revert "tty: n_gsm: avoid call of sleeping functions from atomic context"
  serial: imx: Add missing .thaw_noirq hook
  tty: serial: fsl_lpuart: don't break the on-going transfer when global reset
  serial: 8250: omap: Flush PM QOS work on remove
  serial: 8250: omap: Fix unpaired pm_runtime_put_sync() in omap8250_remove()
  serial: 8250_omap: remove wait loop from Errata i202 workaround
  serial: 8250: omap: Fix missing PM runtime calls for omap8250_set_mctrl()
  serial: 8250: 8250_omap: Avoid RS485 RTS glitch on ->set_termios()

Documentation/driver-api/miscellaneous.rst

@@ -16,12 +16,11 @@ Parallel Port Devices
 16x50 UART Driver
 =================
 
-.. kernel-doc:: drivers/tty/serial/serial_core.c
-   :export:
-
 .. kernel-doc:: drivers/tty/serial/8250/8250_core.c
    :export:
 
+See serial/driver.rst for related APIs.
+
 Pulse-Width Modulation (PWM)
 ============================
 

drivers/tty/n_gsm.c

@@ -264,7 +264,7 @@ struct gsm_mux {
 	bool constipated;		/* Asked by remote to shut up */
 	bool has_devices;		/* Devices were registered */
 
-	struct mutex tx_mutex;
+	spinlock_t tx_lock;
 	unsigned int tx_bytes;		/* TX data outstanding */
 #define TX_THRESH_HI		8192
 #define TX_THRESH_LO		2048
@@ -272,7 +272,7 @@ struct gsm_mux {
 	struct list_head tx_data_list;	/* Pending data packets */
 
 	/* Control messages */
-	struct delayed_work kick_timeout;	/* Kick TX queuing on timeout */
+	struct timer_list kick_timer;	/* Kick TX queuing on timeout */
 	struct timer_list t2_timer;	/* Retransmit timer for commands */
 	int cretries;			/* Command retry counter */
 	struct gsm_control *pending_cmd;/* Our current pending command */
@@ -700,6 +700,7 @@ static int gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 	struct gsm_msg *msg;
 	u8 *dp;
 	int ocr;
+	unsigned long flags;
 
 	msg = gsm_data_alloc(gsm, addr, 0, control);
 	if (!msg)
@@ -721,10 +722,10 @@ static int gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 
 	gsm_print_packet("Q->", addr, cr, control, NULL, 0);
 
-	mutex_lock(&gsm->tx_mutex);
+	spin_lock_irqsave(&gsm->tx_lock, flags);
 	list_add_tail(&msg->list, &gsm->tx_ctrl_list);
 	gsm->tx_bytes += msg->len;
-	mutex_unlock(&gsm->tx_mutex);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 	gsmld_write_trigger(gsm);
 
 	return 0;
@@ -749,7 +750,7 @@ static void gsm_dlci_clear_queues(struct gsm_mux *gsm, struct gsm_dlci *dlci)
 	spin_unlock_irqrestore(&dlci->lock, flags);
 
 	/* Clear data packets in MUX write queue */
-	mutex_lock(&gsm->tx_mutex);
+	spin_lock_irqsave(&gsm->tx_lock, flags);
 	list_for_each_entry_safe(msg, nmsg, &gsm->tx_data_list, list) {
 		if (msg->addr != addr)
 			continue;
@@ -757,7 +758,7 @@ static void gsm_dlci_clear_queues(struct gsm_mux *gsm, struct gsm_dlci *dlci)
 		list_del(&msg->list);
 		kfree(msg);
 	}
-	mutex_unlock(&gsm->tx_mutex);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 }
 
 /**
@@ -1028,7 +1029,7 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 	gsm->tx_bytes += msg->len;
 
 	gsmld_write_trigger(gsm);
-	schedule_delayed_work(&gsm->kick_timeout, 10 * gsm->t1 * HZ / 100);
+	mod_timer(&gsm->kick_timer, jiffies + 10 * gsm->t1 * HZ / 100);
 }
 
 /**
@@ -1043,9 +1044,10 @@ static void __gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 
 static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
 {
-	mutex_lock(&dlci->gsm->tx_mutex);
+	unsigned long flags;
+	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
 	__gsm_data_queue(dlci, msg);
-	mutex_unlock(&dlci->gsm->tx_mutex);
+	spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
 }
 
 /**
@@ -1057,7 +1059,7 @@ static void gsm_data_queue(struct gsm_dlci *dlci, struct gsm_msg *msg)
  *	is data. Keep to the MRU of the mux. This path handles the usual tty
  *	interface which is a byte stream with optional modem data.
  *
- *	Caller must hold the tx_mutex of the mux.
+ *	Caller must hold the tx_lock of the mux.
  */
 
 static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
@@ -1117,7 +1119,7 @@ static int gsm_dlci_data_output(struct gsm_mux *gsm, struct gsm_dlci *dlci)
  *	is data. Keep to the MRU of the mux. This path handles framed data
  *	queued as skbuffs to the DLCI.
  *
- *	Caller must hold the tx_mutex of the mux.
+ *	Caller must hold the tx_lock of the mux.
  */
 
 static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
@@ -1133,7 +1135,7 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
 	if (dlci->adaption == 4)
 		overhead = 1;
 
-	/* dlci->skb is locked by tx_mutex */
+	/* dlci->skb is locked by tx_lock */
 	if (dlci->skb == NULL) {
 		dlci->skb = skb_dequeue_tail(&dlci->skb_list);
 		if (dlci->skb == NULL)
@@ -1187,7 +1189,7 @@ static int gsm_dlci_data_output_framed(struct gsm_mux *gsm,
  *	Push an empty frame in to the transmit queue to update the modem status
  *	bits and to transmit an optional break.
  *
- *	Caller must hold the tx_mutex of the mux.
+ *	Caller must hold the tx_lock of the mux.
  */
 
 static int gsm_dlci_modem_output(struct gsm_mux *gsm, struct gsm_dlci *dlci,
@@ -1301,12 +1303,13 @@ static int gsm_dlci_data_sweep(struct gsm_mux *gsm)
 
 static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
 {
+	unsigned long flags;
 	int sweep;
 
 	if (dlci->constipated)
 		return;
 
-	mutex_lock(&dlci->gsm->tx_mutex);
+	spin_lock_irqsave(&dlci->gsm->tx_lock, flags);
 	/* If we have nothing running then we need to fire up */
 	sweep = (dlci->gsm->tx_bytes < TX_THRESH_LO);
 	if (dlci->gsm->tx_bytes == 0) {
@@ -1317,7 +1320,7 @@ static void gsm_dlci_data_kick(struct gsm_dlci *dlci)
 	}
 	if (sweep)
 		gsm_dlci_data_sweep(dlci->gsm);
-	mutex_unlock(&dlci->gsm->tx_mutex);
+	spin_unlock_irqrestore(&dlci->gsm->tx_lock, flags);
 }
 
 /*
@@ -1708,7 +1711,7 @@ static struct gsm_control *gsm_control_send(struct gsm_mux *gsm,
 		unsigned int command, u8 *data, int clen)
 {
 	struct gsm_control *ctrl = kzalloc(sizeof(struct gsm_control),
-						GFP_KERNEL);
+						GFP_ATOMIC);
 	unsigned long flags;
 	if (ctrl == NULL)
 		return NULL;
@@ -2019,23 +2022,24 @@ static void gsm_dlci_command(struct gsm_dlci *dlci, const u8 *data, int len)
 }
 
 /**
- *	gsm_kick_timeout	-	transmit if possible
- *	@work: work contained in our gsm object
+ *	gsm_kick_timer	-	transmit if possible
+ *	@t: timer contained in our gsm object
  *
  *	Transmit data from DLCIs if the queue is empty. We can't rely on
  *	a tty wakeup except when we filled the pipe so we need to fire off
  *	new data ourselves in other cases.
  */
-static void gsm_kick_timeout(struct work_struct *work)
+static void gsm_kick_timer(struct timer_list *t)
 {
-	struct gsm_mux *gsm = container_of(work, struct gsm_mux, kick_timeout.work);
+	struct gsm_mux *gsm = from_timer(gsm, t, kick_timer);
+	unsigned long flags;
 	int sent = 0;
 
-	mutex_lock(&gsm->tx_mutex);
+	spin_lock_irqsave(&gsm->tx_lock, flags);
 	/* If we have nothing running then we need to fire up */
 	if (gsm->tx_bytes < TX_THRESH_LO)
 		sent = gsm_dlci_data_sweep(gsm);
-	mutex_unlock(&gsm->tx_mutex);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 
 	if (sent && debug & DBG_DATA)
 		pr_info("%s TX queue stalled\n", __func__);
@@ -2492,7 +2496,7 @@ static void gsm_cleanup_mux(struct gsm_mux *gsm, bool disc)
 	}
 
 	/* Finish outstanding timers, making sure they are done */
-	cancel_delayed_work_sync(&gsm->kick_timeout);
+	del_timer_sync(&gsm->kick_timer);
 	del_timer_sync(&gsm->t2_timer);
 
 	/* Finish writing to ldisc */
@@ -2565,7 +2569,6 @@ static void gsm_free_mux(struct gsm_mux *gsm)
 			break;
 		}
 	}
-	mutex_destroy(&gsm->tx_mutex);
 	mutex_destroy(&gsm->mutex);
 	kfree(gsm->txframe);
 	kfree(gsm->buf);
@@ -2637,15 +2640,15 @@ static struct gsm_mux *gsm_alloc_mux(void)
 	}
 	spin_lock_init(&gsm->lock);
 	mutex_init(&gsm->mutex);
-	mutex_init(&gsm->tx_mutex);
 	kref_init(&gsm->ref);
 	INIT_LIST_HEAD(&gsm->tx_ctrl_list);
 	INIT_LIST_HEAD(&gsm->tx_data_list);
-	INIT_DELAYED_WORK(&gsm->kick_timeout, gsm_kick_timeout);
+	timer_setup(&gsm->kick_timer, gsm_kick_timer, 0);
 	timer_setup(&gsm->t2_timer, gsm_control_retransmit, 0);
 	INIT_WORK(&gsm->tx_work, gsmld_write_task);
 	init_waitqueue_head(&gsm->event);
 	spin_lock_init(&gsm->control_lock);
+	spin_lock_init(&gsm->tx_lock);
 
 	gsm->t1 = T1;
 	gsm->t2 = T2;
@@ -2670,7 +2673,6 @@ static struct gsm_mux *gsm_alloc_mux(void)
 	}
 	spin_unlock(&gsm_mux_lock);
 	if (i == MAX_MUX) {
-		mutex_destroy(&gsm->tx_mutex);
 		mutex_destroy(&gsm->mutex);
 		kfree(gsm->txframe);
 		kfree(gsm->buf);
@@ -2826,16 +2828,17 @@ static void gsmld_write_trigger(struct gsm_mux *gsm)
 static void gsmld_write_task(struct work_struct *work)
 {
 	struct gsm_mux *gsm = container_of(work, struct gsm_mux, tx_work);
+	unsigned long flags;
 	int i, ret;
 
 	/* All outstanding control channel and control messages and one data
 	 * frame is sent.
 	 */
 	ret = -ENODEV;
-	mutex_lock(&gsm->tx_mutex);
+	spin_lock_irqsave(&gsm->tx_lock, flags);
 	if (gsm->tty)
 		ret = gsm_data_kick(gsm);
-	mutex_unlock(&gsm->tx_mutex);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 
 	if (ret >= 0)
 		for (i = 0; i < NUM_DLCI; i++)
@@ -3042,6 +3045,7 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
 			   const unsigned char *buf, size_t nr)
 {
 	struct gsm_mux *gsm = tty->disc_data;
+	unsigned long flags;
 	int space;
 	int ret;
 
@@ -3049,13 +3053,13 @@ static ssize_t gsmld_write(struct tty_struct *tty, struct file *file,
 		return -ENODEV;
 
 	ret = -ENOBUFS;
-	mutex_lock(&gsm->tx_mutex);
+	spin_lock_irqsave(&gsm->tx_lock, flags);
 	space = tty_write_room(tty);
 	if (space >= nr)
 		ret = tty->ops->write(tty, buf, nr);
 	else
 		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
-	mutex_unlock(&gsm->tx_mutex);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 
 	return ret;
 }
@@ -3352,13 +3356,14 @@ static struct tty_ldisc_ops tty_ldisc_packet = {
 static void gsm_modem_upd_via_data(struct gsm_dlci *dlci, u8 brk)
 {
 	struct gsm_mux *gsm = dlci->gsm;
+	unsigned long flags;
 
 	if (dlci->state != DLCI_OPEN || dlci->adaption != 2)
 		return;
 
-	mutex_lock(&gsm->tx_mutex);
+	spin_lock_irqsave(&gsm->tx_lock, flags);
 	gsm_dlci_modem_output(gsm, dlci, brk);
-	mutex_unlock(&gsm->tx_mutex);
+	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 }
 
 /**

drivers/tty/serial/8250/8250_lpss.c

@@ -174,6 +174,8 @@ static int ehl_serial_setup(struct lpss8250 *lpss, struct uart_port *port)
 	 */
 	up->dma = dma;
 
+	lpss->dma_maxburst = 16;
+
 	port->set_termios = dw8250_do_set_termios;
 
 	return 0;
@@ -277,8 +279,13 @@ static int lpss8250_dma_setup(struct lpss8250 *lpss, struct uart_8250_port *port
 	struct dw_dma_slave *rx_param, *tx_param;
 	struct device *dev = port->port.dev;
 
-	if (!lpss->dma_param.dma_dev)
+	if (!lpss->dma_param.dma_dev) {
+		dma = port->dma;
+		if (dma)
+			goto out_configuration_only;
+
 		return 0;
+	}
 
 	rx_param = devm_kzalloc(dev, sizeof(*rx_param), GFP_KERNEL);
 	if (!rx_param)
@@ -289,16 +296,18 @@ static int lpss8250_dma_setup(struct lpss8250 *lpss, struct uart_8250_port *port
 		return -ENOMEM;
 
 	*rx_param = lpss->dma_param;
-	dma->rxconf.src_maxburst = lpss->dma_maxburst;
-
 	*tx_param = lpss->dma_param;
-	dma->txconf.dst_maxburst = lpss->dma_maxburst;
 
 	dma->fn = lpss8250_dma_filter;
 	dma->rx_param = rx_param;
 	dma->tx_param = tx_param;
 
 	port->dma = dma;
+
+out_configuration_only:
+	dma->rxconf.src_maxburst = lpss->dma_maxburst;
+	dma->txconf.dst_maxburst = lpss->dma_maxburst;
+
 	return 0;
 }
 

drivers/tty/serial/8250/8250_omap.c

@@ -157,7 +157,11 @@ static u32 uart_read(struct uart_8250_port *up, u32 reg)
 	return readl(up->port.membase + (reg << up->port.regshift));
 }
 
-static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
+/*
+ * Called on runtime PM resume path from omap8250_restore_regs(), and
+ * omap8250_set_mctrl().
+ */
+static void __omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
 {
 	struct uart_8250_port *up = up_to_u8250p(port);
 	struct omap8250_priv *priv = up->port.private_data;
@@ -181,6 +185,20 @@ static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
 	}
 }
 
+static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
+{
+	int err;
+
+	err = pm_runtime_resume_and_get(port->dev);
+	if (err)
+		return;
+
+	__omap8250_set_mctrl(port, mctrl);
+
+	pm_runtime_mark_last_busy(port->dev);
+	pm_runtime_put_autosuspend(port->dev);
+}
+
 /*
  * Work Around for Errata i202 (2430, 3430, 3630, 4430 and 4460)
  * The access to uart register after MDR1 Access
@@ -193,27 +211,10 @@ static void omap8250_set_mctrl(struct uart_port *port, unsigned int mctrl)
 static void omap_8250_mdr1_errataset(struct uart_8250_port *up,
 				     struct omap8250_priv *priv)
 {
-	u8 timeout = 255;
-
 	serial_out(up, UART_OMAP_MDR1, priv->mdr1);
 	udelay(2);
 	serial_out(up, UART_FCR, up->fcr | UART_FCR_CLEAR_XMIT |
 			UART_FCR_CLEAR_RCVR);
-	/*
-	 * Wait for FIFO to empty: when empty, RX_FIFO_E bit is 0 and
-	 * TX_FIFO_E bit is 1.
-	 */
-	while (UART_LSR_THRE != (serial_in(up, UART_LSR) &
-				(UART_LSR_THRE | UART_LSR_DR))) {
-		timeout--;
-		if (!timeout) {
-			/* Should *never* happen. we warn and carry on */
-			dev_crit(up->port.dev, "Errata i202: timedout %x\n",
-				 serial_in(up, UART_LSR));
-			break;
-		}
-		udelay(1);
-	}
 }
 
 static void omap_8250_get_divisor(struct uart_port *port, unsigned int baud,
@@ -292,6 +293,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 {
 	struct omap8250_priv *priv = up->port.private_data;
 	struct uart_8250_dma	*dma = up->dma;
+	u8 mcr = serial8250_in_MCR(up);
 
 	if (dma && dma->tx_running) {
 		/*
@@ -308,7 +310,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	serial_out(up, UART_EFR, UART_EFR_ECB);
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_A);
-	serial8250_out_MCR(up, UART_MCR_TCRTLR);
+	serial8250_out_MCR(up, mcr | UART_MCR_TCRTLR);
 	serial_out(up, UART_FCR, up->fcr);
 
 	omap8250_update_scr(up, priv);
@@ -324,7 +326,8 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 	serial_out(up, UART_LCR, 0);
 
 	/* drop TCR + TLR access, we setup XON/XOFF later */
-	serial8250_out_MCR(up, up->mcr);
+	serial8250_out_MCR(up, mcr);
+
 	serial_out(up, UART_IER, up->ier);
 
 	serial_out(up, UART_LCR, UART_LCR_CONF_MODE_B);
@@ -341,7 +344,7 @@ static void omap8250_restore_regs(struct uart_8250_port *up)
 
 	omap8250_update_mdr1(up, priv);
 
-	up->port.ops->set_mctrl(&up->port, up->port.mctrl);
+	__omap8250_set_mctrl(&up->port, up->port.mctrl);
 
 	if (up->port.rs485.flags & SER_RS485_ENABLED)
 		serial8250_em485_stop_tx(up);
@@ -669,7 +672,6 @@ static int omap_8250_startup(struct uart_port *port)
 
 	pm_runtime_get_sync(port->dev);
 
-	up->mcr = 0;
 	serial_out(up, UART_FCR, UART_FCR_CLEAR_RCVR | UART_FCR_CLEAR_XMIT);
 
 	serial_out(up, UART_LCR, UART_LCR_WLEN8);
@@ -1458,9 +1460,15 @@ static int omap8250_probe(struct platform_device *pdev)
 static int omap8250_remove(struct platform_device *pdev)
 {
 	struct omap8250_priv *priv = platform_get_drvdata(pdev);
+	int err;
+
+	err = pm_runtime_resume_and_get(&pdev->dev);
+	if (err)
+		return err;
 
 	pm_runtime_dont_use_autosuspend(&pdev->dev);
 	pm_runtime_put_sync(&pdev->dev);
+	flush_work(&priv->qos_work);
 	pm_runtime_disable(&pdev->dev);
 	serial8250_unregister_port(priv->line);
 	cpu_latency_qos_remove_request(&priv->pm_qos_request);

drivers/tty/serial/8250/8250_port.c

@@ -1897,10 +1897,13 @@ EXPORT_SYMBOL_GPL(serial8250_modem_status);
 static bool handle_rx_dma(struct uart_8250_port *up, unsigned int iir)
 {
 	switch (iir & 0x3f) {
-	case UART_IIR_RX_TIMEOUT:
-		serial8250_rx_dma_flush(up);
+	case UART_IIR_RDI:
+		if (!up->dma->rx_running)
+			break;
 		fallthrough;
 	case UART_IIR_RLSI:
+	case UART_IIR_RX_TIMEOUT:
+		serial8250_rx_dma_flush(up);
 		return true;
 	}
 	return up->dma->rx_dma(up);

drivers/tty/serial/fsl_lpuart.c

@@ -12,6 +12,7 @@
 #include <linux/dmaengine.h>
 #include <linux/dmapool.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/irq.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -404,33 +405,6 @@ static unsigned int lpuart_get_baud_clk_rate(struct lpuart_port *sport)
 #define lpuart_enable_clks(x)	__lpuart_enable_clks(x, true)
 #define lpuart_disable_clks(x)	__lpuart_enable_clks(x, false)
 
-static int lpuart_global_reset(struct lpuart_port *sport)
-{
-	struct uart_port *port = &sport->port;
-	void __iomem *global_addr;
-	int ret;
-
-	if (uart_console(port))
-		return 0;
-
-	ret = clk_prepare_enable(sport->ipg_clk);
-	if (ret) {
-		dev_err(sport->port.dev, "failed to enable uart ipg clk: %d\n", ret);
-		return ret;
-	}
-
-	if (is_imx7ulp_lpuart(sport) || is_imx8qxp_lpuart(sport)) {
-		global_addr = port->membase + UART_GLOBAL - IMX_REG_OFF;
-		writel(UART_GLOBAL_RST, global_addr);
-		usleep_range(GLOBAL_RST_MIN_US, GLOBAL_RST_MAX_US);
-		writel(0, global_addr);
-		usleep_range(GLOBAL_RST_MIN_US, GLOBAL_RST_MAX_US);
-	}
-
-	clk_disable_unprepare(sport->ipg_clk);
-	return 0;
-}
-
 static void lpuart_stop_tx(struct uart_port *port)
 {
 	unsigned char temp;
@@ -2636,6 +2610,54 @@ static const struct serial_rs485 lpuart_rs485_supported = {
 	/* delay_rts_* and RX_DURING_TX are not supported */
 };
 
+static int lpuart_global_reset(struct lpuart_port *sport)
+{
+	struct uart_port *port = &sport->port;
+	void __iomem *global_addr;
+	unsigned long ctrl, bd;
+	unsigned int val = 0;
+	int ret;
+
+	ret = clk_prepare_enable(sport->ipg_clk);
+	if (ret) {
+		dev_err(sport->port.dev, "failed to enable uart ipg clk: %d\n", ret);
+		return ret;
+	}
+
+	if (is_imx7ulp_lpuart(sport) || is_imx8qxp_lpuart(sport)) {
+		/*
+		 * If the transmitter is used by earlycon, wait for transmit engine to
+		 * complete and then reset.
+		 */
+		ctrl = lpuart32_read(port, UARTCTRL);
+		if (ctrl & UARTCTRL_TE) {
+			bd = lpuart32_read(&sport->port, UARTBAUD);
+			if (read_poll_timeout(lpuart32_tx_empty, val, val, 1, 100000, false,
+					      port)) {
+				dev_warn(sport->port.dev,
+					 "timeout waiting for transmit engine to complete\n");
+				clk_disable_unprepare(sport->ipg_clk);
+				return 0;
+			}
+		}
+
+		global_addr = port->membase + UART_GLOBAL - IMX_REG_OFF;
+		writel(UART_GLOBAL_RST, global_addr);
+		usleep_range(GLOBAL_RST_MIN_US, GLOBAL_RST_MAX_US);
+		writel(0, global_addr);
+		usleep_range(GLOBAL_RST_MIN_US, GLOBAL_RST_MAX_US);
+
+		/* Recover the transmitter for earlycon. */
+		if (ctrl & UARTCTRL_TE) {
+			lpuart32_write(port, bd, UARTBAUD);
+			lpuart32_write(port, ctrl, UARTCTRL);
+		}
+	}
+
+	clk_disable_unprepare(sport->ipg_clk);
+	return 0;
+}
+
 static int lpuart_probe(struct platform_device *pdev)
 {
 	const struct lpuart_soc_data *sdata = of_device_get_match_data(&pdev->dev);

drivers/tty/serial/imx.c

@@ -2594,6 +2594,7 @@ static const struct dev_pm_ops imx_uart_pm_ops = {
 	.suspend_noirq = imx_uart_suspend_noirq,
 	.resume_noirq = imx_uart_resume_noirq,
 	.freeze_noirq = imx_uart_suspend_noirq,
+	.thaw_noirq = imx_uart_resume_noirq,
 	.restore_noirq = imx_uart_resume_noirq,
 	.suspend = imx_uart_suspend,
 	.resume = imx_uart_resume,