Commit b35f8dbb authored by Hugo Villeneuve's avatar Hugo Villeneuve Committed by Greg Kroah-Hartman
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serial: max310x: prevent infinite while() loop in port startup 



If there is a problem after resetting a port, the do/while() loop that
checks the default value of DIVLSB register may run forever and spam the
I2C bus.

Add a delay before each read of DIVLSB, and a maximum number of tries to
prevent that situation from happening.

Also fail probe if port reset is unsuccessful.

Fixes: 10d8b34a ("serial: max310x: Driver rework")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarHugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240116213001.3691629-5-hugo@hugovil.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 8afa6c6d

drivers/tty/serial/max310x.c

+18 −2
Original line number Diff line number Diff line
@@ -237,6 +237,10 @@ 
#define MAX310x_REV_MASK		(0xf8)

#define MAX310X_WRITE_BIT		0x80



/* Port startup definitions */

#define MAX310X_PORT_STARTUP_WAIT_RETRIES	20 /* Number of retries */

#define MAX310X_PORT_STARTUP_WAIT_DELAY_MS	10 /* Delay between retries */



/* Crystal-related definitions */

#define MAX310X_XTAL_WAIT_RETRIES	20 /* Number of retries */

#define MAX310X_XTAL_WAIT_DELAY_MS	10 /* Delay between retries */
@@ -1346,6 +1350,9 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty 
		goto out_clk;



	for (i = 0; i < devtype->nr; i++) {

		bool started = false;

		unsigned int try = 0, val = 0;



		/* Reset port */

		regmap_write(regmaps[i], MAX310X_MODE2_REG,

			     MAX310X_MODE2_RST_BIT);
@@ -1354,8 +1361,17 @@ static int max310x_probe(struct device *dev, const struct max310x_devtype *devty 


		/* Wait for port startup */

		do {

			regmap_read(regmaps[i], MAX310X_BRGDIVLSB_REG, &ret);

		} while (ret != 0x01);

			msleep(MAX310X_PORT_STARTUP_WAIT_DELAY_MS);

			regmap_read(regmaps[i], MAX310X_BRGDIVLSB_REG, &val);



			if (val == 0x01)

				started = true;

		} while (!started && (++try < MAX310X_PORT_STARTUP_WAIT_RETRIES));



		if (!started) {

			ret = dev_err_probe(dev, -EAGAIN, "port reset failed\n");

			goto out_uart;

		}



		regmap_write(regmaps[i], MAX310X_MODE1_REG, devtype->mode1);

	}