Merge tag 'tty-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial driver updates from Greg KH:
 "Even in this age, people are still making new serial port silicon,
  why...

  Anyway, here's the TTY and Serial driver update for 5.4-rc1. Lots of
  changes in here for a number of embedded serial port devices that are
  being worked on because people really like to see those console
  logs...

  Other than that, nothing major here, no core tty changes that anyone
  should care about.

  All of these have been in linux-next for a while with no reported
  issues"

* tag 'tty-5.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (125 commits)
  serial: tegra: Add PIO mode support
  serial: tegra: report clk rate errors
  serial: tegra: add support to adjust baud rate
  serial: tegra: DT for Adjusted baud rates
  serial: tegra: add support to use 8 bytes trigger
  serial: tegra: set maximum num of uart ports to 8
  serial: tegra: check for FIFO mode enabled status
  dt-binding: serial: tegra: add new chips
  serial: tegra: report error to upper tty layer
  serial: tegra: flush the RX fifo on frame error
  serial: tegra: avoid reg access when clk disabled
  serial: tegra: add support to ignore read
  serial: sprd: correct the wrong sequence of arguments
  dt-bindings: serial: Convert riscv,sifive-serial to json-schema
  serial: max310x: turn off transmitter before activating AutoCTS or auto transmitter flow control
  serial: max310x: Properly set flags in AutoCTS mode
  tty: serial: fix platform_no_drv_owner.cocci warnings
  dt-bindings: serial: Document Freescale LINFlexD UART
  serial: fsl_linflexuart: Update compatible string
  tty: n_gsm: avoid recursive locking with async port hangup
  ...

46 files changed, 3026 insertions, 1798 deletions

diff --git a/drivers/tty/hvc/hvcs.c b/drivers/tty/hvc/hvcs.c
index 5fb214e67d73..ee0604cd9c6b 100644
--- a/drivers/tty/hvc/hvcs.c
+++ b/drivers/tty/hvc/hvcs.c
@@ -871,8 +871,8 @@ static void hvcs_set_pi(struct hvcs_partner_info *pi, struct hvcs_struct *hvcsd)
 	hvcsd->p_partition_ID  = pi->partition_ID;
 
 	/* copy the null-term char too */
-	strlcpy(&hvcsd->p_location_code[0],
-			&pi->location_code[0], sizeof(hvcsd->p_location_code));
+	strlcpy(hvcsd->p_location_code, pi->location_code,
+		sizeof(hvcsd->p_location_code));
 }
 
 /*
diff --git a/drivers/tty/isicom.c b/drivers/tty/isicom.c
index e04a43e89f6b..fc38f96475bf 100644
--- a/drivers/tty/isicom.c
+++ b/drivers/tty/isicom.c
@@ -553,7 +553,6 @@ static irqreturn_t isicom_interrupt(int irq, void *dev_id)
 
 	tty = tty_port_tty_get(&port->port);
 	if (tty == NULL) {
-		word_count = byte_count >> 1;
 		while (byte_count > 1) {
 			inw(base);
 			byte_count -= 2;
diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c
index c4e16b31f9ab..36a3eb4ad4c5 100644
--- a/drivers/tty/n_gsm.c
+++ b/drivers/tty/n_gsm.c
@@ -1716,7 +1716,7 @@ static void gsm_dlci_release(struct gsm_dlci *dlci)
 		gsm_destroy_network(dlci);
 		mutex_unlock(&dlci->mutex);
 
-		tty_vhangup(tty);
+		tty_hangup(tty);
 
 		tty_port_tty_set(&dlci->port, NULL);
 		tty_kref_put(tty);
@@ -2171,6 +2171,16 @@ static inline void mux_put(struct gsm_mux *gsm)
 	kref_put(&gsm->ref, gsm_free_muxr);
 }
 
+static inline unsigned int mux_num_to_base(struct gsm_mux *gsm)
+{
+	return gsm->num * NUM_DLCI;
+}
+
+static inline unsigned int mux_line_to_num(unsigned int line)
+{
+	return line / NUM_DLCI;
+}
+
 /**
  *	gsm_alloc_mux		-	allocate a mux
  *
@@ -2351,7 +2361,8 @@ static int gsmld_output(struct gsm_mux *gsm, u8 *data, int len)
 
 static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 {
-	int ret, i, base;
+	unsigned int base;
+	int ret, i;
 
 	gsm->tty = tty_kref_get(tty);
 	gsm->output = gsmld_output;
@@ -2361,7 +2372,7 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 	else {
 		/* Don't register device 0 - this is the control channel and not
 		   a usable tty interface */
-		base = gsm->num << 6; /* Base for this MUX */
+		base = mux_num_to_base(gsm); /* Base for this MUX */
 		for (i = 1; i < NUM_DLCI; i++)
 			tty_register_device(gsm_tty_driver, base + i, NULL);
 	}
@@ -2379,8 +2390,8 @@ static int gsmld_attach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 
 static void gsmld_detach_gsm(struct tty_struct *tty, struct gsm_mux *gsm)
 {
+	unsigned int base = mux_num_to_base(gsm); /* Base for this MUX */
 	int i;
-	int base = gsm->num << 6; /* Base for this MUX */
 
 	WARN_ON(tty != gsm->tty);
 	for (i = 1; i < NUM_DLCI; i++)
@@ -2602,6 +2613,7 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
 {
 	struct gsm_config c;
 	struct gsm_mux *gsm = tty->disc_data;
+	unsigned int base;
 
 	switch (cmd) {
 	case GSMIOC_GETCONF:
@@ -2613,6 +2625,9 @@ static int gsmld_ioctl(struct tty_struct *tty, struct file *file,
 		if (copy_from_user(&c, (void *)arg, sizeof(c)))
 			return -EFAULT;
 		return gsm_config(gsm, &c);
+	case GSMIOC_GETFIRST:
+		base = mux_num_to_base(gsm);
+		return put_user(base + 1, (__u32 __user *)arg);
 	default:
 		return n_tty_ioctl_helper(tty, file, cmd, arg);
 	}
@@ -2908,7 +2923,7 @@ static int gsmtty_install(struct tty_driver *driver, struct tty_struct *tty)
 	struct gsm_mux *gsm;
 	struct gsm_dlci *dlci;
 	unsigned int line = tty->index;
-	unsigned int mux = line >> 6;
+	unsigned int mux = mux_line_to_num(line);
 	bool alloc = false;
 	int ret;
 
diff --git a/drivers/tty/nozomi.c b/drivers/tty/nozomi.c
index 3214e22e79f3..ed99948f3b7f 100644
--- a/drivers/tty/nozomi.c
+++ b/drivers/tty/nozomi.c
@@ -1282,7 +1282,7 @@ static void nozomi_setup_private_data(struct nozomi *dc)
 static ssize_t card_type_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
-	const struct nozomi *dc = pci_get_drvdata(to_pci_dev(dev));
+	const struct nozomi *dc = dev_get_drvdata(dev);
 
 	return sprintf(buf, "%d\n", dc->card_type);
 }
@@ -1291,7 +1291,7 @@ static DEVICE_ATTR_RO(card_type);
 static ssize_t open_ttys_show(struct device *dev, struct device_attribute *attr,
 			  char *buf)
 {
-	const struct nozomi *dc = pci_get_drvdata(to_pci_dev(dev));
+	const struct nozomi *dc = dev_get_drvdata(dev);
 
 	return sprintf(buf, "%u\n", dc->open_ttys);
 }
diff --git a/drivers/tty/serial/8250/8250_bcm2835aux.c b/drivers/tty/serial/8250/8250_bcm2835aux.c
index bd53661103eb..8ce700c1a7fc 100644
--- a/drivers/tty/serial/8250/8250_bcm2835aux.c
+++ b/drivers/tty/serial/8250/8250_bcm2835aux.c
@@ -56,10 +56,8 @@ static int bcm2835aux_serial_probe(struct platform_device *pdev)
 
 	/* get the interrupt */
 	ret = platform_get_irq(pdev, 0);
-	if (ret < 0) {
-		dev_err(&pdev->dev, "irq not found - %i", ret);
+	if (ret < 0)
 		return ret;
-	}
 	data->uart.port.irq = ret;
 
 	/* map the main registers */
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c
index df3bcc0b2d74..e682390ce0de 100644
--- a/drivers/tty/serial/8250/8250_core.c
+++ b/drivers/tty/serial/8250/8250_core.c
@@ -1026,10 +1026,8 @@ int serial8250_register_8250_port(struct uart_8250_port *up)
 		if (!has_acpi_companion(uart->port.dev)) {
 			gpios = mctrl_gpio_init(&uart->port, 0);
 			if (IS_ERR(gpios)) {
-				if (PTR_ERR(gpios) != -ENOSYS) {
-					ret = PTR_ERR(gpios);
-					goto out_unlock;
-				}
+				ret = PTR_ERR(gpios);
+				goto out_unlock;
 			} else {
 				uart->gpios = gpios;
 			}
diff --git a/drivers/tty/serial/8250/8250_dw.c b/drivers/tty/serial/8250/8250_dw.c
index 284e8d052fc3..1c72fdc2dd37 100644
--- a/drivers/tty/serial/8250/8250_dw.c
+++ b/drivers/tty/serial/8250/8250_dw.c
@@ -27,66 +27,36 @@
 
 #include <asm/byteorder.h>
 
-#include "8250.h"
+#include "8250_dwlib.h"
 
 /* Offsets for the DesignWare specific registers */
 #define DW_UART_USR	0x1f /* UART Status Register */
-#define DW_UART_DLF	0xc0 /* Divisor Latch Fraction Register */
-#define DW_UART_CPR	0xf4 /* Component Parameter Register */
-#define DW_UART_UCV	0xf8 /* UART Component Version */
-
-/* Component Parameter Register bits */
-#define DW_UART_CPR_ABP_DATA_WIDTH	(3 << 0)
-#define DW_UART_CPR_AFCE_MODE		(1 << 4)
-#define DW_UART_CPR_THRE_MODE		(1 << 5)
-#define DW_UART_CPR_SIR_MODE		(1 << 6)
-#define DW_UART_CPR_SIR_LP_MODE		(1 << 7)
-#define DW_UART_CPR_ADDITIONAL_FEATURES	(1 << 8)
-#define DW_UART_CPR_FIFO_ACCESS		(1 << 9)
-#define DW_UART_CPR_FIFO_STAT		(1 << 10)
-#define DW_UART_CPR_SHADOW		(1 << 11)
-#define DW_UART_CPR_ENCODED_PARMS	(1 << 12)
-#define DW_UART_CPR_DMA_EXTRA		(1 << 13)
-#define DW_UART_CPR_FIFO_MODE		(0xff << 16)
-/* Helper for fifo size calculation */
-#define DW_UART_CPR_FIFO_SIZE(a)	(((a >> 16) & 0xff) * 16)
 
 /* DesignWare specific register fields */
 #define DW_UART_MCR_SIRE		BIT(6)
 
 struct dw8250_data {
+	struct dw8250_port_data	data;
+
 	u8			usr_reg;
-	u8			dlf_size;
-	int			line;
 	int			msr_mask_on;
 	int			msr_mask_off;
 	struct clk		*clk;
 	struct clk		*pclk;
 	struct reset_control	*rst;
-	struct uart_8250_dma	dma;
 
 	unsigned int		skip_autocfg:1;
 	unsigned int		uart_16550_compatible:1;
 };
 
-static inline u32 dw8250_readl_ext(struct uart_port *p, int offset)
+static inline struct dw8250_data *to_dw8250_data(struct dw8250_port_data *data)
 {
-	if (p->iotype == UPIO_MEM32BE)
-		return ioread32be(p->membase + offset);
-	return readl(p->membase + offset);
-}
-
-static inline void dw8250_writel_ext(struct uart_port *p, int offset, u32 reg)
-{
-	if (p->iotype == UPIO_MEM32BE)
-		iowrite32be(reg, p->membase + offset);
-	else
-		writel(reg, p->membase + offset);
+	return container_of(data, struct dw8250_data, data);
 }
 
 static inline int dw8250_modify_msr(struct uart_port *p, int offset, int value)
 {
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 
 	/* Override any modem control signals if needed */
 	if (offset == UART_MSR) {
@@ -160,7 +130,7 @@ static void dw8250_tx_wait_empty(struct uart_port *p)
 
 static void dw8250_serial_out38x(struct uart_port *p, int offset, int value)
 {
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 
 	/* Allow the TX to drain before we reconfigure */
 	if (offset == UART_LCR)
@@ -175,7 +145,7 @@ static void dw8250_serial_out38x(struct uart_port *p, int offset, int value)
 
 static void dw8250_serial_out(struct uart_port *p, int offset, int value)
 {
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 
 	writeb(value, p->membase + (offset << p->regshift));
 
@@ -202,7 +172,7 @@ static unsigned int dw8250_serial_inq(struct uart_port *p, int offset)
 
 static void dw8250_serial_outq(struct uart_port *p, int offset, int value)
 {
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 
 	value &= 0xff;
 	__raw_writeq(value, p->membase + (offset << p->regshift));
@@ -216,7 +186,7 @@ static void dw8250_serial_outq(struct uart_port *p, int offset, int value)
 
 static void dw8250_serial_out32(struct uart_port *p, int offset, int value)
 {
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 
 	writel(value, p->membase + (offset << p->regshift));
 
@@ -233,7 +203,7 @@ static unsigned int dw8250_serial_in32(struct uart_port *p, int offset)
 
 static void dw8250_serial_out32be(struct uart_port *p, int offset, int value)
 {
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 
 	iowrite32be(value, p->membase + (offset << p->regshift));
 
@@ -252,7 +222,7 @@ static unsigned int dw8250_serial_in32be(struct uart_port *p, int offset)
 static int dw8250_handle_irq(struct uart_port *p)
 {
 	struct uart_8250_port *up = up_to_u8250p(p);
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 	unsigned int iir = p->serial_in(p, UART_IIR);
 	unsigned int status;
 	unsigned long flags;
@@ -306,7 +276,7 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,
 			       struct ktermios *old)
 {
 	unsigned int baud = tty_termios_baud_rate(termios);
-	struct dw8250_data *d = p->private_data;
+	struct dw8250_data *d = to_dw8250_data(p->private_data);
 	long rate;
 	int ret;
 
@@ -368,37 +338,6 @@ static bool dw8250_idma_filter(struct dma_chan *chan, void *param)
 	return param == chan->device->dev;
 }
 
-/*
- * divisor = div(I) + div(F)
- * "I" means integer, "F" means fractional
- * quot = div(I) = clk / (16 * baud)
- * frac = div(F) * 2^dlf_size
- *
- * let rem = clk % (16 * baud)
- * we have: div(F) * (16 * baud) = rem
- * so frac = 2^dlf_size * rem / (16 * baud) = (rem << dlf_size) / (16 * baud)
- */
-static unsigned int dw8250_get_divisor(struct uart_port *p,
-				       unsigned int baud,
-				       unsigned int *frac)
-{
-	unsigned int quot, rem, base_baud = baud * 16;
-	struct dw8250_data *d = p->private_data;
-
-	quot = p->uartclk / base_baud;
-	rem = p->uartclk % base_baud;
-	*frac = DIV_ROUND_CLOSEST(rem << d->dlf_size, base_baud);
-
-	return quot;
-}
-
-static void dw8250_set_divisor(struct uart_port *p, unsigned int baud,
-			       unsigned int quot, unsigned int quot_frac)
-{
-	dw8250_writel_ext(p, DW_UART_DLF, quot_frac);
-	serial8250_do_set_divisor(p, baud, quot, quot_frac);
-}
-
 static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 {
 	if (p->dev->of_node) {
@@ -437,65 +376,18 @@ static void dw8250_quirks(struct uart_port *p, struct dw8250_data *data)
 	/* Platforms with iDMA 64-bit */
 	if (platform_get_resource_byname(to_platform_device(p->dev),
 					 IORESOURCE_MEM, "lpss_priv")) {
-		data->dma.rx_param = p->dev->parent;
-		data->dma.tx_param = p->dev->parent;
-		data->dma.fn = dw8250_idma_filter;
-	}
-}
-
-static void dw8250_setup_port(struct uart_port *p)
-{
-	struct uart_8250_port *up = up_to_u8250p(p);
-	u32 reg;
-
-	/*
-	 * If the Component Version Register returns zero, we know that
-	 * ADDITIONAL_FEATURES are not enabled. No need to go any further.
-	 */
-	reg = dw8250_readl_ext(p, DW_UART_UCV);
-	if (!reg)
-		return;
-
-	dev_dbg(p->dev, "Designware UART version %c.%c%c\n",
-		(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
-
-	dw8250_writel_ext(p, DW_UART_DLF, ~0U);
-	reg = dw8250_readl_ext(p, DW_UART_DLF);
-	dw8250_writel_ext(p, DW_UART_DLF, 0);
-
-	if (reg) {
-		struct dw8250_data *d = p->private_data;
-
-		d->dlf_size = fls(reg);
-		p->get_divisor = dw8250_get_divisor;
-		p->set_divisor = dw8250_set_divisor;
-	}
-
-	reg = dw8250_readl_ext(p, DW_UART_CPR);
-	if (!reg)
-		return;
-
-	/* Select the type based on fifo */
-	if (reg & DW_UART_CPR_FIFO_MODE) {
-		p->type = PORT_16550A;
-		p->flags |= UPF_FIXED_TYPE;
-		p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
-		up->capabilities = UART_CAP_FIFO;
+		data->data.dma.rx_param = p->dev->parent;
+		data->data.dma.tx_param = p->dev->parent;
+		data->data.dma.fn = dw8250_idma_filter;
 	}
-
-	if (reg & DW_UART_CPR_AFCE_MODE)
-		up->capabilities |= UART_CAP_AFE;
-
-	if (reg & DW_UART_CPR_SIR_MODE)
-		up->capabilities |= UART_CAP_IRDA;
 }
 
 static int dw8250_probe(struct platform_device *pdev)
 {
-	struct uart_8250_port uart = {};
+	struct uart_8250_port uart = {}, *up = &uart;
 	struct resource *regs = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 	int irq = platform_get_irq(pdev, 0);
-	struct uart_port *p = &uart.port;
+	struct uart_port *p = &up->port;
 	struct device *dev = &pdev->dev;
 	struct dw8250_data *data;
 	int err;
@@ -534,9 +426,9 @@ static int dw8250_probe(struct platform_device *pdev)
 	if (!data)
 		return -ENOMEM;
 
-	data->dma.fn = dw8250_fallback_dma_filter;
+	data->data.dma.fn = dw8250_fallback_dma_filter;
 	data->usr_reg = DW_UART_USR;
-	p->private_data = data;
+	p->private_data = &data->data;
 
 	data->uart_16550_compatible = device_property_read_bool(dev,
 						"snps,uart-16550-compatible");
@@ -632,14 +524,14 @@ static int dw8250_probe(struct platform_device *pdev)
 
 	/* If we have a valid fifosize, try hooking up DMA */
 	if (p->fifosize) {
-		data->dma.rxconf.src_maxburst = p->fifosize / 4;
-		data->dma.txconf.dst_maxburst = p->fifosize / 4;
-		uart.dma = &data->dma;
+		data->data.dma.rxconf.src_maxburst = p->fifosize / 4;
+		data->data.dma.txconf.dst_maxburst = p->fifosize / 4;
+		up->dma = &data->data.dma;
 	}
 
-	data->line = serial8250_register_8250_port(&uart);
-	if (data->line < 0) {
-		err = data->line;
+	data->data.line = serial8250_register_8250_port(up);
+	if (data->data.line < 0) {
+		err = data->data.line;
 		goto err_reset;
 	}
 
@@ -667,10 +559,11 @@ err_clk:
 static int dw8250_remove(struct platform_device *pdev)
 {
 	struct dw8250_data *data = platform_get_drvdata(pdev);
+	struct device *dev = &pdev->dev;
 
-	pm_runtime_get_sync(&pdev->dev);
+	pm_runtime_get_sync(dev);
 
-	serial8250_unregister_port(data->line);
+	serial8250_unregister_port(data->data.line);
 
 	reset_control_assert(data->rst);
 
@@ -680,8 +573,8 @@ static int dw8250_remove(struct platform_device *pdev)
 	if (!IS_ERR(data->clk))
 		clk_disable_unprepare(data->clk);
 
-	pm_runtime_disable(&pdev->dev);
-	pm_runtime_put_noidle(&pdev->dev);
+	pm_runtime_disable(dev);
+	pm_runtime_put_noidle(dev);
 
 	return 0;
 }
@@ -691,7 +584,7 @@ static int dw8250_suspend(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);
 
-	serial8250_suspend_port(data->line);
+	serial8250_suspend_port(data->data.line);
 
 	return 0;
 }
@@ -700,7 +593,7 @@ static int dw8250_resume(struct device *dev)
 {
 	struct dw8250_data *data = dev_get_drvdata(dev);
 
-	serial8250_resume_port(data->line);
+	serial8250_resume_port(data->data.line);
 
 	return 0;
 }
diff --git a/drivers/tty/serial/8250/8250_dwlib.c b/drivers/tty/serial/8250/8250_dwlib.c
new file mode 100644
index 000000000000..6d6a78eead3e
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_dwlib.c
@@ -0,0 +1,126 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Synopsys DesignWare 8250 library. */
+
+#include <linux/bitops.h>
+#include <linux/device.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/serial_8250.h>
+#include <linux/serial_core.h>
+
+#include "8250_dwlib.h"
+
+/* Offsets for the DesignWare specific registers */
+#define DW_UART_DLF	0xc0 /* Divisor Latch Fraction Register */
+#define DW_UART_CPR	0xf4 /* Component Parameter Register */
+#define DW_UART_UCV	0xf8 /* UART Component Version */
+
+/* Component Parameter Register bits */
+#define DW_UART_CPR_ABP_DATA_WIDTH	(3 << 0)
+#define DW_UART_CPR_AFCE_MODE		(1 << 4)
+#define DW_UART_CPR_THRE_MODE		(1 << 5)
+#define DW_UART_CPR_SIR_MODE		(1 << 6)
+#define DW_UART_CPR_SIR_LP_MODE		(1 << 7)
+#define DW_UART_CPR_ADDITIONAL_FEATURES	(1 << 8)
+#define DW_UART_CPR_FIFO_ACCESS		(1 << 9)
+#define DW_UART_CPR_FIFO_STAT		(1 << 10)
+#define DW_UART_CPR_SHADOW		(1 << 11)
+#define DW_UART_CPR_ENCODED_PARMS	(1 << 12)
+#define DW_UART_CPR_DMA_EXTRA		(1 << 13)
+#define DW_UART_CPR_FIFO_MODE		(0xff << 16)
+
+/* Helper for FIFO size calculation */
+#define DW_UART_CPR_FIFO_SIZE(a)	(((a >> 16) & 0xff) * 16)
+
+static inline u32 dw8250_readl_ext(struct uart_port *p, int offset)
+{
+	if (p->iotype == UPIO_MEM32BE)
+		return ioread32be(p->membase + offset);
+	return readl(p->membase + offset);
+}
+
+static inline void dw8250_writel_ext(struct uart_port *p, int offset, u32 reg)
+{
+	if (p->iotype == UPIO_MEM32BE)
+		iowrite32be(reg, p->membase + offset);
+	else
+		writel(reg, p->membase + offset);
+}
+
+/*
+ * divisor = div(I) + div(F)
+ * "I" means integer, "F" means fractional
+ * quot = div(I) = clk / (16 * baud)
+ * frac = div(F) * 2^dlf_size
+ *
+ * let rem = clk % (16 * baud)
+ * we have: div(F) * (16 * baud) = rem
+ * so frac = 2^dlf_size * rem / (16 * baud) = (rem << dlf_size) / (16 * baud)
+ */
+static unsigned int dw8250_get_divisor(struct uart_port *p, unsigned int baud,
+				       unsigned int *frac)
+{
+	unsigned int quot, rem, base_baud = baud * 16;
+	struct dw8250_port_data *d = p->private_data;
+
+	quot = p->uartclk / base_baud;
+	rem = p->uartclk % base_baud;
+	*frac = DIV_ROUND_CLOSEST(rem << d->dlf_size, base_baud);
+
+	return quot;
+}
+
+static void dw8250_set_divisor(struct uart_port *p, unsigned int baud,
+			       unsigned int quot, unsigned int quot_frac)
+{
+	dw8250_writel_ext(p, DW_UART_DLF, quot_frac);
+	serial8250_do_set_divisor(p, baud, quot, quot_frac);
+}
+
+void dw8250_setup_port(struct uart_port *p)
+{
+	struct uart_8250_port *up = up_to_u8250p(p);
+	u32 reg;
+
+	/*
+	 * If the Component Version Register returns zero, we know that
+	 * ADDITIONAL_FEATURES are not enabled. No need to go any further.
+	 */
+	reg = dw8250_readl_ext(p, DW_UART_UCV);
+	if (!reg)
+		return;
+
+	dev_dbg(p->dev, "Designware UART version %c.%c%c\n",
+		(reg >> 24) & 0xff, (reg >> 16) & 0xff, (reg >> 8) & 0xff);
+
+	dw8250_writel_ext(p, DW_UART_DLF, ~0U);
+	reg = dw8250_readl_ext(p, DW_UART_DLF);
+	dw8250_writel_ext(p, DW_UART_DLF, 0);
+
+	if (reg) {
+		struct dw8250_port_data *d = p->private_data;
+
+		d->dlf_size = fls(reg);
+		p->get_divisor = dw8250_get_divisor;
+		p->set_divisor = dw8250_set_divisor;
+	}
+
+	reg = dw8250_readl_ext(p, DW_UART_CPR);
+	if (!reg)
+		return;
+
+	/* Select the type based on FIFO */
+	if (reg & DW_UART_CPR_FIFO_MODE) {
+		p->type = PORT_16550A;
+		p->flags |= UPF_FIXED_TYPE;
+		p->fifosize = DW_UART_CPR_FIFO_SIZE(reg);
+		up->capabilities = UART_CAP_FIFO;
+	}
+
+	if (reg & DW_UART_CPR_AFCE_MODE)
+		up->capabilities |= UART_CAP_AFE;
+
+	if (reg & DW_UART_CPR_SIR_MODE)
+		up->capabilities |= UART_CAP_IRDA;
+}
+EXPORT_SYMBOL_GPL(dw8250_setup_port);
diff --git a/drivers/tty/serial/8250/8250_dwlib.h b/drivers/tty/serial/8250/8250_dwlib.h
new file mode 100644
index 000000000000..87a4db2a8aba
--- /dev/null
+++ b/drivers/tty/serial/8250/8250_dwlib.h
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: GPL-2.0+
+/* Synopsys DesignWare 8250 library header file. */
+
+#include <linux/types.h>
+
+#include "8250.h"
+
+struct dw8250_port_data {
+	/* Port properties */
+	int			line;
+
+	/* DMA operations */
+	struct uart_8250_dma	dma;
+
+	/* Hardware configuration */
+	u8			dlf_size;
+};
+
+void dw8250_setup_port(struct uart_port *p);
diff --git a/drivers/tty/serial/8250/8250_exar.c b/drivers/tty/serial/8250/8250_exar.c
index edd6dfe055bf..597eb9d16f21 100644
--- a/drivers/tty/serial/8250/8250_exar.c
+++ b/drivers/tty/serial/8250/8250_exar.c
@@ -19,6 +19,7 @@
 #include <linux/string.h>
 #include <linux/tty.h>
 #include <linux/8250_pci.h>
+#include <linux/delay.h>
 
 #include <asm/byteorder.h>
 
@@ -36,6 +37,8 @@
 
 #define UART_EXAR_INT0		0x80
 #define UART_EXAR_8XMODE	0x88	/* 8X sampling rate select */
+#define UART_EXAR_SLEEP		0x8b	/* Sleep mode */
+#define UART_EXAR_DVID		0x8d	/* Device identification */
 
 #define UART_EXAR_FCTR		0x08	/* Feature Control Register */
 #define UART_FCTR_EXAR_IRDA	0x10	/* IrDa data encode select */
@@ -127,18 +130,95 @@ struct exar8250 {
 	int			line[0];
 };
 
+static