Merge tag 'tty-6.10-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

Pull tty/serial fixes from Greg KH:
 "Here are some small TTY and Serial driver fixes that missed the
  6.9-final merge window, but have been in my tree for weeks (my fault,
  travel caused me to miss this)

  These fixes include:

   - more n_gsm fixes for reported problems

   - 8520_mtk driver fix

   - 8250_bcm7271 driver fix

   - sc16is7xx driver fix

  All of these have been in linux-next for weeks without any reported
  problems"

* tag 'tty-6.10-rc1-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty:
  serial: sc16is7xx: fix bug in sc16is7xx_set_baud() when using prescaler
  serial: 8250_bcm7271: use default_mux_rate if possible
  serial: 8520_mtk: Set RTS on shutdown for Rx in-band wakeup
  tty: n_gsm: fix missing receive state reset after mode switch
  tty: n_gsm: fix possible out-of-bounds in gsm0_receive()

3 files changed, 84 insertions, 48 deletions

diff --git a/drivers/tty/serial/8250/8250_bcm7271.c b/drivers/tty/serial/8250/8250_bcm7271.c
index de270863eb5e..2569ca69223f 100644
--- a/drivers/tty/serial/8250/8250_bcm7271.c
+++ b/drivers/tty/serial/8250/8250_bcm7271.c
@@ -673,18 +673,46 @@ static void init_real_clk_rates(struct device *dev, struct brcmuart_priv *priv)
 	clk_set_rate(priv->baud_mux_clk, priv->default_mux_rate);
 }
 
+static u32 find_quot(struct device *dev, u32 freq, u32 baud, u32 *percent)
+{
+	u32 quot;
+	u32 rate;
+	u64 hires_rate;
+	u64 hires_baud;
+	u64 hires_err;
+
+	rate = freq / 16;
+	quot = DIV_ROUND_CLOSEST(rate, baud);
+	if (!quot)
+		return 0;
+
+	/* increase resolution to get xx.xx percent */
+	hires_rate = div_u64((u64)rate * 10000, (u64)quot);
+	hires_baud = (u64)baud * 10000;
+
+	/* get the delta */
+	if (hires_rate > hires_baud)
+		hires_err = (hires_rate - hires_baud);
+	else
+		hires_err = (hires_baud - hires_rate);
+
+	*percent = (unsigned long)DIV_ROUND_CLOSEST_ULL(hires_err, baud);
+
+	dev_dbg(dev, "Baud rate: %u, MUX Clk: %u, Error: %u.%u%%\n",
+		baud, freq, *percent / 100, *percent % 100);
+
+	return quot;
+}
+
 static void set_clock_mux(struct uart_port *up, struct brcmuart_priv *priv,
 			u32 baud)
 {
 	u32 percent;
 	u32 best_percent = UINT_MAX;
 	u32 quot;
+	u32 freq;
 	u32 best_quot = 1;
-	u32 rate;
-	int best_index = -1;
-	u64 hires_rate;
-	u64 hires_baud;
-	u64 hires_err;
+	u32 best_freq = 0;
 	int rc;
 	int i;
 	int real_baud;
@@ -693,44 +721,35 @@ static void set_clock_mux(struct uart_port *up, struct brcmuart_priv *priv,
 	if (priv->baud_mux_clk == NULL)
 		return;
 
-	/* Find the closest match for specified baud */
-	for (i = 0; i < ARRAY_SIZE(priv->real_rates); i++) {
-		if (priv->real_rates[i] == 0)
-			continue;
-		rate = priv->real_rates[i] / 16;
-		quot = DIV_ROUND_CLOSEST(rate, baud);
-		if (!quot)
-			continue;
-
-		/* increase resolution to get xx.xx percent */
-		hires_rate = (u64)rate * 10000;
-		hires_baud = (u64)baud * 10000;
-
-		hires_err = div_u64(hires_rate, (u64)quot);
-
-		/* get the delta */
-		if (hires_err > hires_baud)
-			hires_err = (hires_err - hires_baud);
-		else
-			hires_err = (hires_baud - hires_err);
-
-		percent = (unsigned long)DIV_ROUND_CLOSEST_ULL(hires_err, baud);
-		dev_dbg(up->dev,
-			"Baud rate: %u, MUX Clk: %u, Error: %u.%u%%\n",
-			baud, priv->real_rates[i], percent / 100,
-			percent % 100);
-		if (percent < best_percent) {
-			best_percent = percent;
-			best_index = i;
-			best_quot = quot;
+	/* Try default_mux_rate first */
+	quot = find_quot(up->dev, priv->default_mux_rate, baud, &percent);
+	if (quot) {
+		best_percent = percent;
+		best_freq = priv->default_mux_rate;
+		best_quot = quot;
+	}
+	/* If more than 1% error, find the closest match for specified baud */
+	if (best_percent > 100) {
+		for (i = 0; i < ARRAY_SIZE(priv->real_rates); i++) {
+			freq = priv->real_rates[i];
+			if (freq == 0 || freq == priv->default_mux_rate)
+				continue;
+			quot = find_quot(up->dev, freq, baud, &percent);
+			if (!quot)
+				continue;
+
+			if (percent < best_percent) {
+				best_percent = percent;
+				best_freq = freq;
+				best_quot = quot;
+			}
 		}
 	}
-	if (best_index == -1) {
+	if (!best_freq) {
 		dev_err(up->dev, "Error, %d BAUD rate is too fast.\n", baud);
 		return;
 	}
-	rate = priv->real_rates[best_index];
-	rc = clk_set_rate(priv->baud_mux_clk, rate);
+	rc = clk_set_rate(priv->baud_mux_clk, best_freq);
 	if (rc)
 		dev_err(up->dev, "Error selecting BAUD MUX clock\n");
 
@@ -739,8 +758,8 @@ static void set_clock_mux(struct uart_port *up, struct brcmuart_priv *priv,
 		dev_err(up->dev, "Error, baud: %d has %u.%u%% error\n",
 			baud, percent / 100, percent % 100);
 
-	real_baud = rate / 16 / best_quot;
-	dev_dbg(up->dev, "Selecting BAUD MUX rate: %u\n", rate);
+	real_baud = best_freq / 16 / best_quot;
+	dev_dbg(up->dev, "Selecting BAUD MUX rate: %u\n", best_freq);
 	dev_dbg(up->dev, "Requested baud: %u, Actual baud: %u\n",
 		baud, real_baud);
 
@@ -749,7 +768,7 @@ static void set_clock_mux(struct uart_port *up, struct brcmuart_priv *priv,
 	i += (i / 2);
 	priv->char_wait = ns_to_ktime(i);
 
-	up->uartclk = rate;
+	up->uartclk = best_freq;
 }
 
 static void brcmstb_set_termios(struct uart_port *up,
diff --git a/drivers/tty/serial/8250/8250_mtk.c b/drivers/tty/serial/8250/8250_mtk.c
index c365a349421a..b9cca210e171 100644
--- a/drivers/tty/serial/8250/8250_mtk.c
+++ b/drivers/tty/serial/8250/8250_mtk.c
@@ -209,15 +209,19 @@ static int mtk8250_startup(struct uart_port *port)
 
 static void mtk8250_shutdown(struct uart_port *port)
 {
-#ifdef CONFIG_SERIAL_8250_DMA
 	struct uart_8250_port *up = up_to_u8250p(port);
 	struct mtk8250_data *data = port->private_data;
+	int irq = data->rx_wakeup_irq;
 
+#ifdef CONFIG_SERIAL_8250_DMA
 	if (up->dma)
 		data->rx_status = DMA_RX_SHUTDOWN;
 #endif
 
-	return serial8250_do_shutdown(port);
+	serial8250_do_shutdown(port);
+
+	if (irq >= 0)
+		serial8250_do_set_mctrl(&up->port, TIOCM_RTS);
 }
 
 static void mtk8250_disable_intrs(struct uart_8250_port *up, int mask)
diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 03cf30e20b75..bf0065d1c8e9 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -555,16 +555,28 @@ static bool sc16is7xx_regmap_noinc(struct device *dev, unsigned int reg)
 	return reg == SC16IS7XX_RHR_REG;
 }
 
+/*
+ * Configure programmable baud rate generator (divisor) according to the
+ * desired baud rate.
+ *
+ * From the datasheet, the divisor is computed according to:
+ *
+ *              XTAL1 input frequency
+ *             -----------------------
+ *                    prescaler
+ * divisor = ---------------------------
+ *            baud-rate x sampling-rate
+ */
 static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 {
 	struct sc16is7xx_one *one = to_sc16is7xx_one(port, port);
 	u8 lcr;
-	u8 prescaler = 0;
+	unsigned int prescaler = 1;
 	unsigned long clk = port->uartclk, div = clk / 16 / baud;
 
 	if (div >= BIT(16)) {
-		prescaler = SC16IS7XX_MCR_CLKSEL_BIT;
-		div /= 4;
+		prescaler = 4;
+		div /= prescaler;
 	}
 
 	/* Enable enhanced features */
@@ -574,9 +586,10 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 			      SC16IS7XX_EFR_ENABLE_BIT);
 	sc16is7xx_efr_unlock(port);
 
+	/* If bit MCR_CLKSEL is set, the divide by 4 prescaler is activated. */
 	sc16is7xx_port_update(port, SC16IS7XX_MCR_REG,
 			      SC16IS7XX_MCR_CLKSEL_BIT,
-			      prescaler);
+			      prescaler == 1 ? 0 : SC16IS7XX_MCR_CLKSEL_BIT);
 
 	/* Backup LCR and access special register set (DLL/DLH) */
 	lcr = sc16is7xx_port_read(port, SC16IS7XX_LCR_REG);
@@ -592,7 +605,7 @@ static int sc16is7xx_set_baud(struct uart_port *port, int baud)
 	/* Restore LCR and access to general register set */
 	sc16is7xx_port_write(port, SC16IS7XX_LCR_REG, lcr);
 
-	return DIV_ROUND_CLOSEST(clk / 16, div);
+	return DIV_ROUND_CLOSEST((clk / prescaler) / 16, div);
 }
 
 static void sc16is7xx_handle_rx(struct uart_port *port, unsigned int rxlen,