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serial: max310x: prevent infinite while() loop in port startup

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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: 10d8b34a42 ("serial: max310x: Driver rework")
Cc: stable@vger.kernel.org
Signed-off-by: Hugo Villeneuve <hvilleneuve@dimonoff.com>
Link: https://lore.kernel.org/r/20240116213001.3691629-5-hugo@hugovil.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Hugo Villeneuve 2024-01-16 16:30:01 -05:00 committed by Greg Kroah-Hartman
parent 8afa6c6dec
commit b35f8dbbce
1 changed files with 18 additions and 2 deletions
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20
drivers/tty/serial/max310x.c
View file

@ -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);
}