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serial: 8250: Fix PM usage_count for console handover
commitf9b11229b7
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 because82586a7215
("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>
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parent
e1bd94dd9e
commit
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3 changed files with 9 additions and 5 deletions
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@ -23,6 +23,7 @@
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#include <linux/sysrq.h>
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#include <linux/sysrq.h>
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#include <linux/delay.h>
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#include <linux/delay.h>
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#include <linux/platform_device.h>
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#include <linux/platform_device.h>
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#include <linux/pm_runtime.h>
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#include <linux/tty.h>
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#include <linux/tty.h>
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#include <linux/ratelimit.h>
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#include <linux/ratelimit.h>
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#include <linux/tty_flip.h>
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#include <linux/tty_flip.h>
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@ -571,6 +572,9 @@ serial8250_register_ports(struct uart_driver *drv, struct device *dev)
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up->port.dev = dev;
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up->port.dev = dev;
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if (uart_console_enabled(&up->port))
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pm_runtime_get_sync(up->port.dev);
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serial8250_apply_quirks(up);
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serial8250_apply_quirks(up);
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uart_add_one_port(drv, &up->port);
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uart_add_one_port(drv, &up->port);
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}
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}
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@ -1941,11 +1941,6 @@ static int uart_proc_show(struct seq_file *m, void *v)
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}
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}
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#endif
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#endif
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static inline bool uart_console_enabled(struct uart_port *port)
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{
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return uart_console(port) && (port->cons->flags & CON_ENABLED);
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}
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static void uart_port_spin_lock_init(struct uart_port *port)
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static void uart_port_spin_lock_init(struct uart_port *port)
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{
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{
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spin_lock_init(&port->lock);
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spin_lock_init(&port->lock);
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@ -394,6 +394,11 @@ static const bool earlycon_acpi_spcr_enable EARLYCON_USED_OR_UNUSED;
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static inline int setup_earlycon(char *buf) { return 0; }
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static inline int setup_earlycon(char *buf) { return 0; }
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#endif
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#endif
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static inline bool uart_console_enabled(struct uart_port *port)
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{
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return uart_console(port) && (port->cons->flags & CON_ENABLED);
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}
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struct uart_port *uart_get_console(struct uart_port *ports, int nr,
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struct uart_port *uart_get_console(struct uart_port *ports, int nr,
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struct console *c);
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struct console *c);
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int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr,
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int uart_parse_earlycon(char *p, unsigned char *iotype, resource_size_t *addr,
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