[PATCH v3 08/11] serial: sc16is7xx: fix regression with GPIO configuration

[Hugo Villeneuve <hugo@xxxxxxxxxxx>]

From: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>

Commit 679875d1d880 ("sc16is7xx: Separate GPIOs from modem control lines")
and commit 21144bab4f11 ("sc16is7xx: Handle modem status lines")
changed the function of the GPIOs pins to act as modem control
lines without any possibility of selecting GPIO function.

As a consequence, applications that depends on GPIO lines configured
by default as GPIO pins no longer work as expected.

Also, the change to select modem control lines function was done only
for channel A of dual UART variants (752/762). This was not documented
in the log message.

This new patch allows to specify GPIO or modem control line function
in the device tree, and for each of the ports (A or B).

This is done by using the new device-tree property named
"modem-control-line-ports" (property added in separate patch).

We also now reduce the number of exported GPIOs according to the
modem-status-line-port DT property.

Boards that need to have GPIOS configured as modem control lines
should add that property to their device tree. Here is a list of
boards using the sc16is7xx driver in their device tree and that may
need to be modified:
    arm64/boot/dts/freescale/fsl-ls1012a-frdm.dts
    mips/boot/dts/ingenic/cu1830-neo.dts
    mips/boot/dts/ingenic/cu1000-neo.dts

Fixes: 679875d1d880 ("sc16is7xx: Separate GPIOs from modem control lines")
Fixes: 21144bab4f11 ("sc16is7xx: Handle modem status lines")
Signed-off-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
---
 drivers/tty/serial/sc16is7xx.c | 65 +++++++++++++++++++++++-----------
 1 file changed, 44 insertions(+), 21 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index a5d8af0f6da0..97ec532a0a19 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -236,7 +236,8 @@
 
 /* IOControl register bits (Only 75x/76x) */
 #define SC16IS7XX_IOCONTROL_LATCH_BIT	(1 << 0) /* Enable input latching */
-#define SC16IS7XX_IOCONTROL_MODEM_BIT	(1 << 1) /* Enable GPIO[7:4] as modem pins */
+#define SC16IS7XX_IOCONTROL_MODEM_A_BIT	(1 << 1) /* Enable GPIO[7:4] as modem A pins */
+#define SC16IS7XX_IOCONTROL_MODEM_B_BIT	(1 << 2) /* Enable GPIO[3:0] as modem B pins */
 #define SC16IS7XX_IOCONTROL_SRESET_BIT	(1 << 3) /* Software Reset */
 
 /* EFCR register bits */
@@ -301,12 +302,12 @@
 /* Misc definitions */
 #define SC16IS7XX_FIFO_SIZE		(64)
 #define SC16IS7XX_REG_SHIFT		2
+#define SC16IS7XX_GPIOS_PER_BANK	4
 
 struct sc16is7xx_devtype {
 	char	name[10];
 	int	nr_gpio;
 	int	nr_uart;
-	int	has_mctrl;
 };
 
 #define SC16IS7XX_RECONF_MD		(1 << 0)
@@ -336,6 +337,7 @@ struct sc16is7xx_port {
 	struct clk			*clk;
 #ifdef CONFIG_GPIOLIB
 	struct gpio_chip		gpio;
+	int				gpio_configured;
 #endif
 	unsigned char			buf[SC16IS7XX_FIFO_SIZE];
 	struct kthread_worker		kworker;
@@ -447,35 +449,30 @@ static const struct sc16is7xx_devtype sc16is74x_devtype = {
 	.name		= "SC16IS74X",
 	.nr_gpio	= 0,
 	.nr_uart	= 1,
-	.has_mctrl	= 0,
 };
 
 static const struct sc16is7xx_devtype sc16is750_devtype = {
 	.name		= "SC16IS750",
-	.nr_gpio	= 4,
+	.nr_gpio	= 8,
 	.nr_uart	= 1,
-	.has_mctrl	= 1,
 };
 
 static const struct sc16is7xx_devtype sc16is752_devtype = {
 	.name		= "SC16IS752",
-	.nr_gpio	= 0,
+	.nr_gpio	= 8,
 	.nr_uart	= 2,
-	.has_mctrl	= 1,
 };
 
 static const struct sc16is7xx_devtype sc16is760_devtype = {
 	.name		= "SC16IS760",
-	.nr_gpio	= 4,
+	.nr_gpio	= 8,
 	.nr_uart	= 1,
-	.has_mctrl	= 1,
 };
 
 static const struct sc16is7xx_devtype sc16is762_devtype = {
 	.name		= "SC16IS762",
-	.nr_gpio	= 0,
+	.nr_gpio	= 8,
 	.nr_uart	= 2,
-	.has_mctrl	= 1,
 };
 
 static bool sc16is7xx_regmap_volatile(struct device *dev, unsigned int reg)
@@ -1396,6 +1393,10 @@ static int sc16is7xx_probe(struct device *dev,
 		return -ENOMEM;
 	}
 
+#ifdef CONFIG_GPIOLIB
+	s->gpio_configured = devtype->nr_gpio;
+#endif /* CONFIG_GPIOLIB */
+
 	/* Always ask for fixed clock rate from a property. */
 	device_property_read_u32(dev, "clock-frequency", &uartclk);
 
@@ -1473,12 +1474,6 @@ static int sc16is7xx_probe(struct device *dev,
 				     SC16IS7XX_EFCR_RXDISABLE_BIT |
 				     SC16IS7XX_EFCR_TXDISABLE_BIT);
 
-		/* Use GPIO lines as modem status registers */
-		if (devtype->has_mctrl)
-			sc16is7xx_port_write(&s->p[i].port,
-					     SC16IS7XX_IOCONTROL_REG,
-					     SC16IS7XX_IOCONTROL_MODEM_BIT);
-
 		/* Initialize kthread work structs */
 		kthread_init_work(&s->p[i].tx_work, sc16is7xx_tx_proc);
 		kthread_init_work(&s->p[i].reg_work, sc16is7xx_reg_proc);
@@ -1514,10 +1509,38 @@ static int sc16is7xx_probe(struct device *dev,
 					 prop, p, u)
 			if (u < devtype->nr_uart)
 				s->p[u].irda_mode = true;
+
+		val = 0;
+
+		of_property_for_each_u32(dev->of_node, "nxp,modem-control-line-ports",
+					 prop, p, u)
+			if (u < devtype->nr_uart) {
+				/* Use GPIO lines as modem control lines */
+				if (u == 0)
+					val |= SC16IS7XX_IOCONTROL_MODEM_A_BIT;
+				else if (u == 1)
+					val |= SC16IS7XX_IOCONTROL_MODEM_B_BIT;
+
+#ifdef CONFIG_GPIOLIB
+				if (s->gpio_configured >=
+				    SC16IS7XX_GPIOS_PER_BANK)
+					s->gpio_configured -=
+						SC16IS7XX_GPIOS_PER_BANK;
+#endif /* CONFIG_GPIOLIB */
+			}
+
+		if (val)
+			regmap_update_bits(
+				s->regmap,
+				SC16IS7XX_IOCONTROL_REG << SC16IS7XX_REG_SHIFT,
+				SC16IS7XX_IOCONTROL_MODEM_A_BIT |
+				SC16IS7XX_IOCONTROL_MODEM_B_BIT, val);
 	}
 
 #ifdef CONFIG_GPIOLIB
-	if (devtype->nr_gpio) {
+	dev_dbg(dev, "GPIOs to configure: %d\n", s->gpio_configured);
+
+	if (s->gpio_configured) {
 		/* Setup GPIO controller */
 		s->gpio.owner		 = THIS_MODULE;
 		s->gpio.parent		 = dev;
@@ -1527,7 +1550,7 @@ static int sc16is7xx_probe(struct device *dev,
 		s->gpio.direction_output = sc16is7xx_gpio_direction_output;
 		s->gpio.set		 = sc16is7xx_gpio_set;
 		s->gpio.base		 = -1;
-		s->gpio.ngpio		 = devtype->nr_gpio;
+		s->gpio.ngpio		 = s->gpio_configured;
 		s->gpio.can_sleep	 = 1;
 		ret = gpiochip_add_data(&s->gpio, s);
 		if (ret)
@@ -1555,7 +1578,7 @@ static int sc16is7xx_probe(struct device *dev,
 		return 0;
 
 #ifdef CONFIG_GPIOLIB
-	if (devtype->nr_gpio)
+	if (s->gpio_configured)
 		gpiochip_remove(&s->gpio);
 
 out_thread:
@@ -1581,7 +1604,7 @@ static void sc16is7xx_remove(struct device *dev)
 	int i;
 
 #ifdef CONFIG_GPIOLIB
-	if (s->devtype->nr_gpio)
+	if (s->gpio_configured)
 		gpiochip_remove(&s->gpio);
 #endif
 
-- 
2.30.2