Ilpo Järvinen d9cb6fabc9 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: bedb404e91 ("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>		2022-07-21 21:20:19 +02:00
..
hvc	tty: hvc: fix return value of __setup handler	2022-04-08 14:40:28 +02:00
ipwireless
serdev
serial	serial: 8250: Fix PM usage_count for console handover	2022-07-21 21:20:19 +02:00
vt	vt: fix memory overlapping when deleting chars in the buffer	2022-07-21 21:20:19 +02:00
amiserial.c
cyclades.c
ehv_bytechan.c
goldfish.c	tty: goldfish: Fix free_irq() on remove	2022-06-22 14:13:16 +02:00
isicom.c
Kconfig
Makefile
mips_ejtag_fdc.c
moxa.c
moxa.h
mxser.c	mxser: fix xmit_buf leak in activate when LSR == 0xff	2022-04-08 14:40:23 +02:00
mxser.h
n_gsm.c	tty: n_gsm: fix mux activation issues in gsm_config()	2022-05-18 10:23:46 +02:00
n_hdlc.c
n_null.c
n_r3964.c
n_tracerouter.c
n_tracesink.c
n_tracesink.h
n_tty.c	tty: n_tty: Restore EOF push handling behavior	2022-06-14 18:32:30 +02:00
nozomi.c
pty.c
rocket_int.h
rocket.c
rocket.h
synclink_gt.c	tty: synclink_gt: Fix null-pointer-dereference in slgt_clean()	2022-06-14 18:32:41 +02:00
synclink.c
synclinkmp.c
sysrq.c	sysrq: do not omit current cpu when showing backtrace of all active CPUs	2022-06-14 18:32:42 +02:00
tty_audit.c
tty_baudrate.c
tty_buffer.c	tty: fix deadlock caused by calling printk() under tty_port->lock	2022-06-09 10:21:17 +02:00
tty_io.c
tty_ioctl.c
tty_jobctrl.c
tty_ldisc.c
tty_ldsem.c
tty_mutex.c
tty_port.c
ttynull.c
vcc.c