From patchwork Fri Dec 27 22:45:21 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: John Ogness X-Patchwork-Id: 853977 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 993F1158525; Fri, 27 Dec 2024 22:45:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735339536; cv=none; b=ET5xHiZPw3tBuwpmGLneXINxPhXu/d1Hm3ZF0ADwEhc5FCXWeWfeBfX/egSJEYdGU9ucB91vaElNtthfHvAPk5mN3HaTpXK6P/8OUu39rrlaT633/lsjQxg6X/TlxG0BBPyKVvLbbwTTAaMkqc3b2KIuxsL6gpZAtPHDJEFQgk4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1735339536; c=relaxed/simple; bh=2ZGiIUgMsPX77GCLFu0Uu1nElWI3oLL1xw1QVNOvoOk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=eTpoRmXIyTuHWIQ31ljR9BBVGr2ZKGLx0tMxx0pkqrH4xbKrYYSkMeppcnGURw6LWC/fNA23oEpoyi9nvoenuzWBBEB2mAiFZ9/L1Qr3//JveoAopUj+BBf2PmJT5Rp3y/r+fJYwhM3wp/gduyan1pmdcIDyr4asaUL4g56RNMQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=qb/StGQ+; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=X4DP2cRt; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="qb/StGQ+"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="X4DP2cRt" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1735339527; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bkeDrc/RBAn/s0ivBR+9zpc2uVkypfbM9hDUcSXv7JU=; b=qb/StGQ+3taS87EFNEtTNh0s8xS6ZSp753xNzf5QuuKaLJtpblQ24jShwNC34o3qj4FIiE ZBvDmBw//JgUKa4ktx+5MTN6eGB8K5R5LfO/kkIU4NCsMiF6SDsPl95gk6AvCIiecFZz4t divwOJtahhkiXNMgKifaqf9zMkWYD27ZboKSRSuLP4ulVZdMvaA7Io3xedhPF9N7IQA38O mgqJqwMdyMJwaVocS+HypwKUP2HnWD9wI7V+jW45gPmNgLiysHJD3lXa1Q4MYB6qi7rTvb Et2f7wsxfaCP/c+MryMYjHylWyLLUPFpeITzbFcEnNZobJ/RWJQ9S5TEU7ZQ/A== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1735339527; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=bkeDrc/RBAn/s0ivBR+9zpc2uVkypfbM9hDUcSXv7JU=; b=X4DP2cRtTuqfiMxO0MKnTimCkQSAnH67BJEDtlW+W5wkPZ0aToyNLFpLpuMqX/qIkgQeGD 3Nx6ObgCsmcf6BAg== To: Greg Kroah-Hartman Cc: Jiri Slaby , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Thomas Gleixner , Esben Haabendal , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, Andy Shevchenko , Matt Turner , Tony Lindgren , Arnd Bergmann , Niklas Schnelle , Serge Semin Subject: [PATCH tty-next v4 5/6] serial: 8250: Switch to nbcon console Date: Fri, 27 Dec 2024 23:51:21 +0106 Message-Id: <20241227224523.28131-6-john.ogness@linutronix.de> In-Reply-To: <20241227224523.28131-1-john.ogness@linutronix.de> References: <20241227224523.28131-1-john.ogness@linutronix.de> Precedence: bulk X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Implement the necessary callbacks to switch the 8250 console driver to perform as an nbcon console. Add implementations for the nbcon console callbacks: ->write_atomic() ->write_thread() ->device_lock() ->device_unlock() and add CON_NBCON to the initial @flags. All register access in the callbacks are within unsafe sections. The ->write_atomic and ->write_therad() callbacks allow safe handover/takeover per byte and add a preceding newline if they take over from another context mid-line. For the ->write_atomic() callback, a new irq_work is used to defer modem control since it may be called from a context that does not allow waking up tasks. Note: A new __serial8250_clear_IER() is introduced for direct clearing of UART_IER. This will allow to restore the lockdep check to serial8250_clear_IER() in a follow-up commit. Signed-off-by: John Ogness --- drivers/tty/serial/8250/8250_core.c | 35 ++++++- drivers/tty/serial/8250/8250_port.c | 149 +++++++++++++++++++++------- include/linux/serial_8250.h | 8 +- 3 files changed, 150 insertions(+), 42 deletions(-) diff --git a/drivers/tty/serial/8250/8250_core.c b/drivers/tty/serial/8250/8250_core.c index 2b70e82dffeb..3d5a2183ff13 100644 --- a/drivers/tty/serial/8250/8250_core.c +++ b/drivers/tty/serial/8250/8250_core.c @@ -388,12 +388,34 @@ void __init serial8250_register_ports(struct uart_driver *drv, struct device *de #ifdef CONFIG_SERIAL_8250_CONSOLE -static void univ8250_console_write(struct console *co, const char *s, - unsigned int count) +static void univ8250_console_write_atomic(struct console *co, + struct nbcon_write_context *wctxt) { struct uart_8250_port *up = &serial8250_ports[co->index]; - serial8250_console_write(up, s, count); + serial8250_console_write(up, wctxt, true); +} + +static void univ8250_console_write_thread(struct console *co, + struct nbcon_write_context *wctxt) +{ + struct uart_8250_port *up = &serial8250_ports[co->index]; + + serial8250_console_write(up, wctxt, false); +} + +static void univ8250_console_device_lock(struct console *co, unsigned long *flags) +{ + struct uart_port *up = &serial8250_ports[co->index].port; + + __uart_port_lock_irqsave(up, flags); +} + +static void univ8250_console_device_unlock(struct console *co, unsigned long flags) +{ + struct uart_port *up = &serial8250_ports[co->index].port; + + __uart_port_unlock_irqrestore(up, flags); } static int univ8250_console_setup(struct console *co, char *options) @@ -494,12 +516,15 @@ static int univ8250_console_match(struct console *co, char *name, int idx, static struct console univ8250_console = { .name = "ttyS", - .write = univ8250_console_write, + .write_atomic = univ8250_console_write_atomic, + .write_thread = univ8250_console_write_thread, + .device_lock = univ8250_console_device_lock, + .device_unlock = univ8250_console_device_unlock, .device = uart_console_device, .setup = univ8250_console_setup, .exit = univ8250_console_exit, .match = univ8250_console_match, - .flags = CON_PRINTBUFFER | CON_ANYTIME, + .flags = CON_PRINTBUFFER | CON_ANYTIME | CON_NBCON, .index = -1, .data = &serial8250_reg, }; diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index e38271f477d1..fbba4746eccc 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -711,7 +711,12 @@ static void serial8250_set_sleep(struct uart_8250_port *p, int sleep) serial8250_rpm_put(p); } -static void serial8250_clear_IER(struct uart_8250_port *up) +/* + * Only to be used directly by the callback helper serial8250_console_write(), + * which may not require the port lock. Use serial8250_clear_IER() instead for + * all other cases. + */ +static void __serial8250_clear_IER(struct uart_8250_port *up) { if (up->capabilities & UART_CAP_UUE) serial_out(up, UART_IER, UART_IER_UUE); @@ -719,6 +724,11 @@ static void serial8250_clear_IER(struct uart_8250_port *up) serial_out(up, UART_IER, 0); } +static inline void serial8250_clear_IER(struct uart_8250_port *up) +{ + __serial8250_clear_IER(up); +} + #ifdef CONFIG_SERIAL_8250_RSA /* * Attempts to turn on the RSA FIFO. Returns zero on failure. @@ -1406,9 +1416,6 @@ void serial8250_em485_stop_tx(struct uart_8250_port *p, bool toggle_ier) { unsigned char mcr = serial8250_in_MCR(p); - /* Port locked to synchronize UART_IER access against the console. */ - lockdep_assert_held_once(&p->port.lock); - if (p->port.rs485.flags & SER_RS485_RTS_AFTER_SEND) mcr |= UART_MCR_RTS; else @@ -1424,6 +1431,12 @@ void serial8250_em485_stop_tx(struct uart_8250_port *p, bool toggle_ier) serial8250_clear_and_reinit_fifos(p); if (toggle_ier) { + /* + * Port locked to synchronize UART_IER access + * against the console + */ + lockdep_assert_held_once(&p->port.lock); + p->ier |= UART_IER_RLSI | UART_IER_RDI; serial_port_out(&p->port, UART_IER, p->ier); } @@ -3302,7 +3315,11 @@ EXPORT_SYMBOL_GPL(serial8250_set_defaults); static void serial8250_console_putchar(struct uart_port *port, unsigned char ch) { + struct uart_8250_port *up = up_to_u8250p(port); + serial_port_out(port, UART_TX, ch); + + up->console_line_ended = (ch == '\n'); } static void serial8250_console_wait_putchar(struct uart_port *port, unsigned char ch) @@ -3339,14 +3356,21 @@ static void serial8250_console_restore(struct uart_8250_port *up) serial8250_out_MCR(up, up->mcr | UART_MCR_DTR | UART_MCR_RTS); } -static void fifo_wait_for_lsr(struct uart_8250_port *up, unsigned int count) +static int fifo_wait_for_lsr(struct uart_8250_port *up, + struct nbcon_write_context *wctxt, + unsigned int count) { unsigned int i; for (i = 0; i < count; i++) { + if (!nbcon_can_proceed(wctxt)) + return -EPERM; + if (wait_for_lsr(up, UART_LSR_THRE)) - return; + return 0; } + + return -ETIMEDOUT; } /* @@ -3356,18 +3380,20 @@ static void fifo_wait_for_lsr(struct uart_8250_port *up, unsigned int count) * to get empty. */ static void serial8250_console_fifo_write(struct uart_8250_port *up, - const char *s, unsigned int count) + struct nbcon_write_context *wctxt) { - const char *end = s + count; unsigned int fifosize = up->tx_loadsz; struct uart_port *port = &up->port; + const char *s = wctxt->outbuf; + const char *end = s + wctxt->len; unsigned int tx_count = 0; bool cr_sent = false; unsigned int i; while (s != end) { /* Allow timeout for each byte of a possibly full FIFO */ - fifo_wait_for_lsr(up, fifosize); + if (fifo_wait_for_lsr(up, wctxt, fifosize) == -EPERM) + return; for (i = 0; i < fifosize && s != end; ++i) { if (*s == '\n' && !cr_sent) { @@ -3385,39 +3411,51 @@ static void serial8250_console_fifo_write(struct uart_8250_port *up, * Allow timeout for each byte written since the caller will only wait * for UART_LSR_BOTH_EMPTY using the timeout of a single character */ - fifo_wait_for_lsr(up, tx_count); + fifo_wait_for_lsr(up, wctxt, tx_count); +} + +static void serial8250_console_byte_write(struct uart_8250_port *up, + struct nbcon_write_context *wctxt) +{ + struct uart_port *port = &up->port; + const char *s = wctxt->outbuf; + const char *end = s + wctxt->len; + + /* + * Write out the message. If a handover or takeover occurs, writing + * must be aborted since wctxt->outbuf and wctxt->len are no longer + * valid. + */ + while (s != end && nbcon_can_proceed(wctxt)) + uart_console_write(port, s++, 1, serial8250_console_wait_putchar); } /* - * Print a string to the serial port trying not to disturb - * any possible real use of the port... + * Print a string to the serial port trying not to disturb + * any possible real use of the port... * - * The console_lock must be held when we get here. - * - * Doing runtime PM is really a bad idea for the kernel console. - * Thus, we assume the function is called when device is powered up. + * Doing runtime PM is really a bad idea for the kernel console. + * Thus, assume it is called when device is powered up. */ -void serial8250_console_write(struct uart_8250_port *up, const char *s, - unsigned int count) +void serial8250_console_write(struct uart_8250_port *up, + struct nbcon_write_context *wctxt, + bool is_atomic) { struct uart_8250_em485 *em485 = up->em485; struct uart_port *port = &up->port; - unsigned long flags; - unsigned int ier, use_fifo; - int locked = 1; - - touch_nmi_watchdog(); + unsigned int ier; + bool use_fifo; - if (oops_in_progress) - locked = uart_port_trylock_irqsave(port, &flags); - else - uart_port_lock_irqsave(port, &flags); + if (!nbcon_enter_unsafe(wctxt)) + return; /* - * First save the IER then disable the interrupts + * First, save the IER, then disable the interrupts. The special + * variant to clear the IER is used because console printing may + * occur without holding the port lock. */ ier = serial_port_in(port, UART_IER); - serial8250_clear_IER(up); + __serial8250_clear_IER(up); /* check scratch reg to see if port powered off during system sleep */ if (up->canary && (up->canary != serial_port_in(port, UART_SCR))) { @@ -3431,6 +3469,14 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, mdelay(port->rs485.delay_rts_before_send); } + /* + * If console printer did not fully output the previous line, it must + * have been handed or taken over. Insert a newline in order to + * maintain clean output. + */ + if (!up->console_line_ended && nbcon_can_proceed(wctxt)) + uart_console_write(port, "\n", 1, serial8250_console_wait_putchar); + use_fifo = (up->capabilities & UART_CAP_FIFO) && /* * BCM283x requires to check the fifo @@ -3452,9 +3498,16 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, !(up->port.flags & UPF_CONS_FLOW); if (likely(use_fifo)) - serial8250_console_fifo_write(up, s, count); + serial8250_console_fifo_write(up, wctxt); else - uart_console_write(port, s, count, serial8250_console_wait_putchar); + serial8250_console_byte_write(up, wctxt); + + /* + * If ownership was lost, this context must reacquire ownership in + * order to perform final actions (such as re-enabling interrupts). + */ + while (!nbcon_enter_unsafe(wctxt)) + nbcon_reacquire_nobuf(wctxt); /* * Finally, wait for transmitter to become empty @@ -3477,11 +3530,18 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, * call it if we have saved something in the saved flags * while processing with interrupts off. */ - if (up->msr_saved_flags) - serial8250_modem_status(up); + if (up->msr_saved_flags) { + /* + * For atomic, it must be deferred to irq_work because this + * may be a context that does not permit waking up tasks. + */ + if (is_atomic) + irq_work_queue(&up->modem_status_work); + else + serial8250_modem_status(up); + } - if (locked) - uart_port_unlock_irqrestore(port, flags); + nbcon_exit_unsafe(wctxt); } static unsigned int probe_baud(struct uart_port *port) @@ -3499,8 +3559,24 @@ static unsigned int probe_baud(struct uart_port *port) return (port->uartclk / 16) / quot; } +/* + * irq_work handler to perform modem control. Only triggered via + * ->write_atomic() callback because it may be in a scheduler or + * NMI context, unable to wake tasks. + */ +static void modem_status_handler(struct irq_work *iwp) +{ + struct uart_8250_port *up = container_of(iwp, struct uart_8250_port, modem_status_work); + struct uart_port *port = &up->port; + + uart_port_lock(port); + serial8250_modem_status(up); + uart_port_unlock(port); +} + int serial8250_console_setup(struct uart_port *port, char *options, bool probe) { + struct uart_8250_port *up = up_to_u8250p(port); int baud = 9600; int bits = 8; int parity = 'n'; @@ -3510,6 +3586,9 @@ int serial8250_console_setup(struct uart_port *port, char *options, bool probe) if (!port->iobase && !port->membase) return -ENODEV; + up->console_line_ended = true; + init_irq_work(&up->modem_status_work, modem_status_handler); + if (options) uart_parse_options(options, &baud, &parity, &bits, &flow); else if (probe) diff --git a/include/linux/serial_8250.h b/include/linux/serial_8250.h index 144de7a7948d..5a804dc5e05e 100644 --- a/include/linux/serial_8250.h +++ b/include/linux/serial_8250.h @@ -150,8 +150,12 @@ struct uart_8250_port { #define LSR_SAVE_FLAGS UART_LSR_BRK_ERROR_BITS u16 lsr_saved_flags; u16 lsr_save_mask; + + bool console_line_ended; /* line fully output */ + #define MSR_SAVE_FLAGS UART_MSR_ANY_DELTA unsigned char msr_saved_flags; + struct irq_work modem_status_work; struct uart_8250_dma *dma; const struct uart_8250_ops *ops; @@ -202,8 +206,8 @@ void serial8250_tx_chars(struct uart_8250_port *up); unsigned int serial8250_modem_status(struct uart_8250_port *up); void serial8250_init_port(struct uart_8250_port *up); void serial8250_set_defaults(struct uart_8250_port *up); -void serial8250_console_write(struct uart_8250_port *up, const char *s, - unsigned int count); +void serial8250_console_write(struct uart_8250_port *up, + struct nbcon_write_context *wctxt, bool in_atomic); int serial8250_console_setup(struct uart_port *port, char *options, bool probe); int serial8250_console_exit(struct uart_port *port);