[PATCH v10 4/6] 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.

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

Do so by using the new device-tree property named
"nxp,modem-control-line-ports" (property added in separate patch).

When registering GPIO chip controller, mask-out GPIO pins declared as
modem control lines according to this new DT property.

Fixes: 679875d1d880 ("sc16is7xx: Separate GPIOs from modem control lines")
Fixes: 21144bab4f11 ("sc16is7xx: Handle modem status lines")
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Hugo Villeneuve <hvilleneuve@xxxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andy.shevchenko@xxxxxxxxx>
Reviewed-by: Lech Perczak <lech.perczak@xxxxxxxxxxxxxxx>
Tested-by: Lech Perczak <lech.perczak@xxxxxxxxxxxxxxx>
---
 drivers/tty/serial/sc16is7xx.c | 143 +++++++++++++++++++++++++--------
 1 file changed, 108 insertions(+), 35 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 93b4137daa8b..b45e34e3910d 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -236,7 +236,8 @@
 
 /* IOControl register bits (Only 750/760) */
 #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)
@@ -336,7 +337,9 @@ struct sc16is7xx_port {
 	struct clk			*clk;
 #ifdef CONFIG_GPIOLIB
 	struct gpio_chip		gpio;
+	unsigned long			gpio_valid_mask;
 #endif
+	u8				mctrl_mask;
 	unsigned char			buf[SC16IS7XX_FIFO_SIZE];
 	struct kthread_worker		kworker;
 	struct task_struct		*kworker_task;
@@ -447,35 +450,30 @@ 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)
@@ -1350,8 +1348,98 @@ static int sc16is7xx_gpio_direction_output(struct gpio_chip *chip,
 
 	return 0;
 }
+
+static int sc16is7xx_gpio_init_valid_mask(struct gpio_chip *chip,
+					  unsigned long *valid_mask,
+					  unsigned int ngpios)
+{
+	struct sc16is7xx_port *s = gpiochip_get_data(chip);
+
+	*valid_mask = s->gpio_valid_mask;
+
+	return 0;
+}
+
+static int sc16is7xx_setup_gpio_chip(struct sc16is7xx_port *s)
+{
+	struct device *dev = s->p[0].port.dev;
+
+	if (!s->devtype->nr_gpio)
+		return 0;
+
+	switch (s->mctrl_mask) {
+	case 0:
+		s->gpio_valid_mask = GENMASK(7, 0);
+		break;
+	case SC16IS7XX_IOCONTROL_MODEM_A_BIT:
+		s->gpio_valid_mask = GENMASK(3, 0);
+		break;
+	case SC16IS7XX_IOCONTROL_MODEM_B_BIT:
+		s->gpio_valid_mask = GENMASK(7, 4);
+		break;
+	default:
+		break;
+	}
+
+	if (s->gpio_valid_mask == 0)
+		return 0;
+
+	s->gpio.owner		 = THIS_MODULE;
+	s->gpio.parent		 = dev;
+	s->gpio.label		 = dev_name(dev);
+	s->gpio.init_valid_mask	 = sc16is7xx_gpio_init_valid_mask;
+	s->gpio.direction_input	 = sc16is7xx_gpio_direction_input;
+	s->gpio.get		 = sc16is7xx_gpio_get;
+	s->gpio.direction_output = sc16is7xx_gpio_direction_output;
+	s->gpio.set		 = sc16is7xx_gpio_set;
+	s->gpio.base		 = -1;
+	s->gpio.ngpio		 = s->devtype->nr_gpio;
+	s->gpio.can_sleep	 = 1;
+
+	return gpiochip_add_data(&s->gpio, s);
+}
 #endif
 
+/*
+ * Configure ports designated to operate as modem control lines.
+ */
+static int sc16is7xx_setup_mctrl_ports(struct sc16is7xx_port *s)
+{
+	int i;
+	int ret;
+	int count;
+	u32 mctrl_port[2];
+	struct device *dev = s->p[0].port.dev;
+
+	count = device_property_count_u32(dev, "nxp,modem-control-line-ports");
+	if (count < 0 || count > ARRAY_SIZE(mctrl_port))
+		return 0;
+
+	ret = device_property_read_u32_array(dev, "nxp,modem-control-line-ports",
+					     mctrl_port, count);
+	if (ret)
+		return ret;
+
+	s->mctrl_mask = 0;
+
+	for (i = 0; i < count; i++) {
+		/* Use GPIO lines as modem control lines */
+		if (mctrl_port[i] == 0)
+			s->mctrl_mask |= SC16IS7XX_IOCONTROL_MODEM_A_BIT;
+		else if (mctrl_port[i] == 1)
+			s->mctrl_mask |= SC16IS7XX_IOCONTROL_MODEM_B_BIT;
+	}
+
+	if (s->mctrl_mask)
+		regmap_update_bits(
+			s->regmap,
+			SC16IS7XX_IOCONTROL_REG << SC16IS7XX_REG_SHIFT,
+			SC16IS7XX_IOCONTROL_MODEM_A_BIT |
+			SC16IS7XX_IOCONTROL_MODEM_B_BIT, s->mctrl_mask);
+
+	return 0;
+}
+
 static const struct serial_rs485 sc16is7xx_rs485_supported = {
 	.flags = SER_RS485_ENABLED | SER_RS485_RTS_AFTER_SEND,
 	.delay_rts_before_send = 1,
@@ -1464,12 +1552,6 @@ 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);
@@ -1507,23 +1589,14 @@ static int sc16is7xx_probe(struct device *dev,
 				s->p[u].irda_mode = true;
 	}
 
+	ret = sc16is7xx_setup_mctrl_ports(s);
+	if (ret)
+		goto out_ports;
+
 #ifdef CONFIG_GPIOLIB
-	if (devtype->nr_gpio) {
-		/* Setup GPIO cotroller */
-		s->gpio.owner		 = THIS_MODULE;
-		s->gpio.parent		 = dev;
-		s->gpio.label		 = dev_name(dev);
-		s->gpio.direction_input	 = sc16is7xx_gpio_direction_input;
-		s->gpio.get		 = sc16is7xx_gpio_get;
-		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.can_sleep	 = 1;
-		ret = gpiochip_add_data(&s->gpio, s);
-		if (ret)
-			goto out_ports;
-	}
+	ret = sc16is7xx_setup_gpio_chip(s);
+	if (ret)
+		goto out_ports;
 #endif
 
 	/*
@@ -1546,7 +1619,7 @@ static int sc16is7xx_probe(struct device *dev,
 		return 0;
 
 #ifdef CONFIG_GPIOLIB
-	if (devtype->nr_gpio)
+	if (s->gpio_valid_mask)
 		gpiochip_remove(&s->gpio);
 #endif
 
@@ -1570,7 +1643,7 @@ static void sc16is7xx_remove(struct device *dev)
 	int i;
 
 #ifdef CONFIG_GPIOLIB
-	if (s->devtype->nr_gpio)
+	if (s->gpio_valid_mask)
 		gpiochip_remove(&s->gpio);
 #endif
 
-- 
2.30.2