From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 18EF2C6FA82 for ; Sat, 10 Sep 2022 22:56:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229691AbiIJW4U (ORCPT ); Sat, 10 Sep 2022 18:56:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36948 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229505AbiIJW4P (ORCPT ); Sat, 10 Sep 2022 18:56:15 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6F1B42AE32 for ; Sat, 10 Sep 2022 15:56:14 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1662850572; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZoaZUiuVv6BWFHO/m2g0FWD+9Or5kBIzh3/01/yDsQo=; b=bYi/U4oQOoJzKcvrEjXqp5vVjwjOzmhwtvXqKQhpVhByvXQlT3rggCwyozTRyKLVzTYSWM UAVUQxzTxKqYePri6C90P0fQRa/zAVaEwzl36NCTI1JQ0stHe4F83i2hx+D2Obn+UYfU7y wOJ9qb+IBk4QEQxRLvsybIyz4WuUxXQBaki6hddx02jw+pPHwHvW/cRhVlILyaaipbL1K7 5OtyeBtjyDFGZys+ALkd4jZxg23FW5YdJHq97sVrpGy+Up/sXh5bzjKUirag5ajNfFTvOf CehX63kJ217oYKgCilQhV1zl1aAgXhgOgpWh8nuIUNW05Q8ZRZnpJpGKV2DcGQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1662850572; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZoaZUiuVv6BWFHO/m2g0FWD+9Or5kBIzh3/01/yDsQo=; b=tJRwI9zq908yfq7rDVmpR5UZlFOgZiWRV511efJJ06yxC9CYZv4mTlvnM2KbGZcgFbVXdD y5jMgAJfj9T3NWAA== To: LKML Cc: John Ogness , Petr Mladek , Sergey Senozhatsky , Steven Rostedt , Linus Torvalds , Peter Zijlstra , "Paul E. McKenney" , Daniel Vetter , Greg Kroah-Hartman , Helge Deller , Jason Wessel , Daniel Thompson Subject: Re: [patch RFC 00/29] printk: A new approach - WIP In-Reply-To: <20220910221947.171557773@linutronix.de> References: <20220910221947.171557773@linutronix.de> Date: Sun, 11 Sep 2022 00:56:11 +0200 Message-ID: <877d2ayh2s.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Sep 11 2022 at 00:27, Thomas Gleixner wrote: > For testing we used the most simple driver: a hacked up version of the > early uart8250 console as we wanted to concentrate on validating the core > mechanisms of friendly handover and hostile takeovers instead of dealing > with the horrors of port locks or whatever at the same time. That's the > next challenge. Hack patch will be provided in a reply. Here you go. --- Subject: serial: 8250: Use 8250 serial for exploring noBKL consoles From: John Ogness Date: Sat, 10 Sep 2022 01:05:34 +0200 From: John Ogness Utilize 8250 early console - the only console in the kernel which is reentrancy and NMI safe - to explore the noBKL console infrastructure. Not-Signed-off-by: John Ogness Not-Signed-off-by: Thomas Gleixner --- drivers/tty/serial/8250/8250_early.c | 32 ++++++++++++++++++++++++++++++++ drivers/tty/serial/8250/Kconfig | 11 ++++++++++- drivers/tty/serial/8250/Makefile | 2 +- 3 files changed, 43 insertions(+), 2 deletions(-) --- a/drivers/tty/serial/8250/8250_early.c +++ b/drivers/tty/serial/8250/8250_early.c @@ -107,6 +107,34 @@ static void early_serial8250_write(struc uart_console_write(port, s, count, serial_putc); } +static bool __early_serial8250_write(struct console *con, struct cons_write_context *wctxt, + unsigned char c) +{ + struct earlycon_device *device = con->data; + struct uart_port *port = &device->port; + unsigned char *s = wctxt->outbuf; + + serial_putc(port, c); + + for (; wctxt->pos < wctxt->len; wctxt->pos++, s++) { + if (!console_can_proceed(wctxt)) + return false; + + uart_console_write(port, s, 1, serial_putc); + } + return true; +} + +static bool early_serial8250_write_thread(struct console *con, struct cons_write_context *wctxt) +{ + return __early_serial8250_write(con, wctxt, 'T'); +} + +static bool early_serial8250_write_atomic(struct console *con, struct cons_write_context *wctxt) +{ + return __early_serial8250_write(con, wctxt, 'A'); +} + #ifdef CONFIG_CONSOLE_POLL static int early_serial8250_read(struct console *console, char *s, unsigned int count) @@ -170,6 +198,10 @@ int __init early_serial8250_setup(struct device->con->write = early_serial8250_write; device->con->read = early_serial8250_read; + device->con->flags &= ~CON_BOOT; + device->con->flags |= CON_NO_BKL; + device->con->write_thread = early_serial8250_write_thread; + device->con->write_atomic = early_serial8250_write_atomic; return 0; } EARLYCON_DECLARE(uart8250, early_serial8250_setup); --- a/drivers/tty/serial/8250/Kconfig +++ b/drivers/tty/serial/8250/Kconfig @@ -82,9 +82,18 @@ config SERIAL_8250_FINTEK If unsure, say N. +config SERIAL_8250_CONSOLE_EARLY + bool "Console on 8250/16550 and compatible noBKL console mockup" + default SERIAL_8250 + select SERIAL_CORE_CONSOLE + select SERIAL_EARLYCON + help + Mockup to demonstrate the core capabilities for noBKL consoles. + OTOH, the _only_ reliable reentrant and NMI safe console... + config SERIAL_8250_CONSOLE bool "Console on 8250/16550 and compatible serial port" - depends on SERIAL_8250=y + depends on SERIAL_8250=y && !SERIAL_8250_CONSOLE_EARLY select SERIAL_CORE_CONSOLE select SERIAL_EARLYCON help --- a/drivers/tty/serial/8250/Makefile +++ b/drivers/tty/serial/8250/Makefile @@ -20,7 +20,7 @@ obj-$(CONFIG_SERIAL_8250_CS) += serial_ obj-$(CONFIG_SERIAL_8250_ACORN) += 8250_acorn.o obj-$(CONFIG_SERIAL_8250_ASPEED_VUART) += 8250_aspeed_vuart.o obj-$(CONFIG_SERIAL_8250_BCM2835AUX) += 8250_bcm2835aux.o -obj-$(CONFIG_SERIAL_8250_CONSOLE) += 8250_early.o +obj-$(CONFIG_SERIAL_8250_CONSOLE_EARLY) += 8250_early.o obj-$(CONFIG_SERIAL_8250_FOURPORT) += 8250_fourport.o obj-$(CONFIG_SERIAL_8250_ACCENT) += 8250_accent.o obj-$(CONFIG_SERIAL_8250_BOCA) += 8250_boca.o