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authorIlpo Järvinen <ilpo.jarvinen@linux.intel.com>2022-06-29 11:48:41 +0200
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2022-06-30 17:17:31 +0200
commitf9b11229b79c0fb2100b5bb4628a101b1d37fbf6 (patch)
tree89ed4b82374218f4a7cfd5a5d0f70256473b333c /include
parentserial: 8250: fix return error code in serial8250_request_std_resource() (diff)
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serial: 8250: Fix PM usage_count for console handover
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>
Diffstat (limited to 'include')
-rw-r--r--include/linux/serial_core.h5
1 files changed, 5 insertions, 0 deletions
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 657a0fc68a3f..fde258b3decd 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -390,6 +390,11 @@ 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,