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From: Hugo Villeneuve <hugo@hugovil.com>
To: gregkh@linuxfoundation.org,
	jirislaby@kernel.org
Cc: linux-kernel@vger.kernel.org,
	linux-serial@vger.kernel.org,
	hugo@hugovil.com,
	Hugo Villeneuve <hvilleneuve@dimonoff.com>
Date: Thu,  7 Mar 2024 11:18:27 -0500
Message-Id: <20240307161828.118495-4-hugo@hugovil.com>
In-Reply-To: <20240307161828.118495-1-hugo@hugovil.com>
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Subject: [PATCH v2 3/4] serial: sc16is7xx: split into core and I2C/SPI parts (sc16is7xx_lines)

From: Hugo Villeneuve <hvilleneuve@dimonoff.com>

Before, sc16is7xx_lines was checked for a free (zero) bit first, and then
later it was set only if UART port registration succeeded.

Now that sc16is7xx_lines is shared for the I2C and SPI drivers, make sure
it is reserved and modified atomically, and use a new variable to hold the
status of UART port regisration.

Remove need to check for previous port registration in sc16is7xx_remove(),
because if sc16is7xx_probe() succeeded, we are guaranteed to have
successfully registered both ports.

Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
---
 drivers/tty/serial/sc16is7xx.c | 22 +++++++++++++++++-----
 1 file changed, 17 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/sc16is7xx.c b/drivers/tty/serial/sc16is7xx.c
index 5b53c88b7133..d81aad1b201d 100644
--- a/drivers/tty/serial/sc16is7xx.c
+++ b/drivers/tty/serial/sc16is7xx.c
@@ -343,6 +343,8 @@ struct sc16is7xx_port {
 
 static DECLARE_BITMAP(sc16is7xx_lines, SC16IS7XX_MAX_DEVS);
 
+static DEFINE_MUTEX(sc16is7xx_lines_lock); /* For probe atomic line reservation. */
+
 static struct uart_driver sc16is7xx_uart = {
 	.owner		= THIS_MODULE,
 	.driver_name    = SC16IS7XX_NAME,
@@ -1468,6 +1470,7 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 	u32 uartclk = 0;
 	int i, ret;
 	struct sc16is7xx_port *s;
+	bool port_registered[SC16IS7XX_MAX_PORTS];
 
 	for (i = 0; i < devtype->nr_uart; i++)
 		if (IS_ERR(regmaps[i]))
@@ -1532,14 +1535,21 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 	regmap_write(regmaps[0], SC16IS7XX_IOCONTROL_REG,
 		     SC16IS7XX_IOCONTROL_SRESET_BIT);
 
+	memset(port_registered, 0, sizeof(port_registered));
+
 	for (i = 0; i < devtype->nr_uart; ++i) {
+		mutex_lock(&sc16is7xx_lines_lock);
 		s->p[i].port.line = find_first_zero_bit(sc16is7xx_lines,
 							SC16IS7XX_MAX_DEVS);
 		if (s->p[i].port.line >= SC16IS7XX_MAX_DEVS) {
 			ret = -ERANGE;
+			mutex_unlock(&sc16is7xx_lines_lock);
 			goto out_ports;
 		}
 
+		set_bit(s->p[i].port.line, sc16is7xx_lines);
+		mutex_unlock(&sc16is7xx_lines_lock);
+
 		/* Initialize port data */
 		s->p[i].port.dev	= dev;
 		s->p[i].port.irq	= irq;
@@ -1584,7 +1594,7 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 		if (ret)
 			goto out_ports;
 
-		set_bit(s->p[i].port.line, sc16is7xx_lines);
+		port_registered[i] = true;
 
 		/* Enable EFR */
 		sc16is7xx_port_write(&s->p[i].port, SC16IS7XX_LCR_REG,
@@ -1642,9 +1652,11 @@ int sc16is7xx_probe(struct device *dev, const struct sc16is7xx_devtype *devtype,
 #endif
 
 out_ports:
-	for (i = 0; i < devtype->nr_uart; i++)
-		if (test_and_clear_bit(s->p[i].port.line, sc16is7xx_lines))
+	for (i = 0; i < devtype->nr_uart; i++) {
+		clear_bit(s->p[i].port.line, sc16is7xx_lines);
+		if (port_registered[i])
 			uart_remove_one_port(&sc16is7xx_uart, &s->p[i].port);
+	}
 
 	kthread_stop(s->kworker_task);
 
@@ -1667,8 +1679,8 @@ void sc16is7xx_remove(struct device *dev)
 
 	for (i = 0; i < s->devtype->nr_uart; i++) {
 		kthread_cancel_delayed_work_sync(&s->p[i].ms_work);
-		if (test_and_clear_bit(s->p[i].port.line, sc16is7xx_lines))
-			uart_remove_one_port(&sc16is7xx_uart, &s->p[i].port);
+		clear_bit(s->p[i].port.line, sc16is7xx_lines);
+		uart_remove_one_port(&sc16is7xx_uart, &s->p[i].port);
 		sc16is7xx_power(&s->p[i].port, 0);
 	}
 
-- 
2.39.2