From ec5ad331680c96ef3dd30dc297b206988023b9e1 Mon Sep 17 00:00:00 2001 From: Max Staudt Date: Sat, 18 Jun 2022 20:01:34 +0200 Subject: tty: Add N_CAN327 line discipline ID for ELM327 based CAN driver The actual driver will be added via the CAN tree. Acked-by: Marc Kleine-Budde Signed-off-by: Max Staudt Link: https://lore.kernel.org/r/20220618180134.9890-1-max@enpas.org Signed-off-by: Greg Kroah-Hartman --- include/uapi/linux/tty.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/uapi/linux/tty.h b/include/uapi/linux/tty.h index 9d0f06bfbac3..68aeae2addec 100644 --- a/include/uapi/linux/tty.h +++ b/include/uapi/linux/tty.h @@ -38,8 +38,9 @@ #define N_NULL 27 /* Null ldisc used for error handling */ #define N_MCTP 28 /* MCTP-over-serial */ #define N_DEVELOPMENT 29 /* Manual out-of-tree testing */ +#define N_CAN327 30 /* ELM327 based OBD-II interfaces */ /* Always the newest line discipline + 1 */ -#define NR_LDISCS 30 +#define NR_LDISCS 31 #endif /* _UAPI_LINUX_TTY_H */ -- cgit v1.2.3 From f9b11229b79c0fb2100b5bb4628a101b1d37fbf6 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ilpo=20J=C3=A4rvinen?= Date: Wed, 29 Jun 2022 12:48:41 +0300 Subject: serial: 8250: Fix PM usage_count for console handover MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Tested-by: Tony Lindgren Reviewed-by: Andy Shevchenko Reviewed-by: Tony Lindgren Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/b4f428e9-491f-daf2-2232-819928dc276e@linux.intel.com Signed-off-by: Greg Kroah-Hartman --- include/linux/serial_core.h | 5 +++++ 1 file changed, 5 insertions(+) (limited to 'include') 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, -- cgit v1.2.3