diff options
| author | Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> | 2022-06-29 12:48:41 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2022-07-21 22:20:19 +0300 |
| commit | d9cb6fabc90102f9e61fe35bd0160db88f4f53b4 (patch) | |
| tree | fd35a53ad0543eb0a57a95ef1d193d735acfd187 | |
| parent | e1bd94dd9e5c63ac7280d67e730061cf684125ba (diff) | |
| download | linux-d9cb6fabc90102f9e61fe35bd0160db88f4f53b4.tar.xz | |
serial: 8250: Fix PM usage_count for console handover
commit f9b11229b79c0fb2100b5bb4628a101b1d37fbf6 upstream.
When console is enabled, univ8250_console_setup() calls
serial8250_console_setup() before .dev is set to uart_port. Therefore,
it will not call pm_runtime_get_sync(). Later, when the actual driver
is going to take over univ8250_console_exit() is called. As .dev is
already set, serial8250_console_exit() makes pm_runtime_put_sync() call
with usage count being zero triggering PM usage count warning
(extra debug for univ8250_console_setup(), univ8250_console_exit(), and
serial8250_register_ports()):
[ 0.068987] univ8250_console_setup ttyS0 nodev
[ 0.499670] printk: console [ttyS0] enabled
[ 0.717955] printk: console [ttyS0] printing thread started
[ 1.960163] serial8250_register_ports assigned dev for ttyS0
[ 1.976830] printk: console [ttyS0] disabled
[ 1.976888] printk: console [ttyS0] printing thread stopped
[ 1.977073] univ8250_console_exit ttyS0 usage:0
[ 1.977075] serial8250 serial8250: Runtime PM usage count underflow!
[ 1.977429] dw-apb-uart.6: ttyS0 at MMIO 0x4010006000 (irq = 33, base_baud = 115200) is a 16550A
[ 1.977812] univ8250_console_setup ttyS0 usage:2
[ 1.978167] printk: console [ttyS0] printing thread started
[ 1.978203] printk: console [ttyS0] enabled
To fix the issue, call pm_runtime_get_sync() in
serial8250_register_ports() as soon as .dev is set for an uart_port
if it has console enabled.
This problem became apparent only recently because 82586a721595 ("PM:
runtime: Avoid device usage count underflows") added the warning
printout. I confirmed this problem also occurs with v5.18 (w/o the
warning printout, obviously).
Fixes: bedb404e91bb ("serial: 8250_port: Don't use power management for kernel console")
Cc: stable <stable@kernel.org>
Tested-by: Tony Lindgren <tony@atomide.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Link: https://lore.kernel.org/r/b4f428e9-491f-daf2-2232-819928dc276e@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | drivers/tty/serial/8250/8250_core.c | 4 | ||||
| -rw-r--r-- | drivers/tty/serial/serial_core.c | 5 | ||||
| -rw-r--r-- | include/linux/serial_core.h | 5 |
3 files changed, 9 insertions, 5 deletions
diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index cae61d1ebec5..98ce484f1089 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -23,6 +23,7 @@ #include <linux/sysrq.h> #include <linux/delay.h> #include <linux/platform_device.h> +#include <linux/pm_runtime.h> #include <linux/tty.h> #include <linux/ratelimit.h> #include <linux/tty_flip.h> @@ -571,6 +572,9 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev) up->port.dev = dev; + if (uart_console_enabled(&up->port)) + pm_runtime_get_sync(up->port.dev); + serial8250_apply_quirks(up); uart_add_one_port(drv, &up->port); } diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c index 32d09d024f6c..b578f7090b63 100644 --- a/drivers/tty/serial/serial_core.c +++ b/drivers/tty/serial/serial_core.c @@ -1941,11 +1941,6 @@ static int uart_proc_show(struct seq_file *m, void *v) } #endif -static inline bool uart_console_enabled(struct uart_port *port) -{ - return uart_console(port) && (port->cons->flags & CON_ENABLED); -} - static void uart_port_spin_lock_init(struct uart_port *port) { spin_lock_init(&port->lock); diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h index 35b26743dbb2..9c1292ea47fd 100644 --- a/include/linux/serial_core.h +++ b/include/linux/serial_core.h @@ -394,6 +394,11 @@ static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED; static inline int setup_earlycon(char *buf) { return 0; } #endif +static inline bool uart_console_enabled(struct uart_port *port) +{ + return uart_console(port) && (port->cons->flags & CON_ENABLED); +} + struct uart_port *uart_get_console(struct uart_port *ports, int nr, struct console *c); int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr, |