From 54ca955b5a4024e2ce0f206b03adb7109bc4da26 Mon Sep 17 00:00:00 2001 From: Pali Rohár Date: Wed, 23 Dec 2020 20:19:31 +0100 Subject: serial: mvebu-uart: fix tx lost characters at power off Commit c685af1108d7 ("serial: mvebu-uart: fix tx lost characters") fixed tx lost characters at low baud rates but started causing tx lost characters when kernel is going to power off or reboot. TX_EMP tells us when transmit queue is empty therefore all characters were transmitted. TX_RDY tells us when CPU can send a new character. Therefore we need to use different check prior transmitting new character and different check after all characters were sent. This patch splits polling code into two functions: wait_for_xmitr() which waits for TX_RDY and wait_for_xmite() which waits for TX_EMP. When rebooting A3720 platform without this patch on UART is print only: [ 42.699� And with this patch on UART is full output: [ 39.530216] reboot: Restarting system Fixes: c685af1108d7 ("serial: mvebu-uart: fix tx lost characters") Signed-off-by: Pali Rohár Cc: stable Link: https://lore.kernel.org/r/20201223191931.18343-1-pali@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/mvebu-uart.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/mvebu-uart.c b/drivers/tty/serial/mvebu-uart.c index 118b29912289..e0c00a1b0763 100644 --- a/drivers/tty/serial/mvebu-uart.c +++ b/drivers/tty/serial/mvebu-uart.c @@ -648,6 +648,14 @@ static void wait_for_xmitr(struct uart_port *port) (val & STAT_TX_RDY(port)), 1, 10000); } +static void wait_for_xmite(struct uart_port *port) +{ + u32 val; + + readl_poll_timeout_atomic(port->membase + UART_STAT, val, + (val & STAT_TX_EMP), 1, 10000); +} + static void mvebu_uart_console_putchar(struct uart_port *port, int ch) { wait_for_xmitr(port); @@ -675,7 +683,7 @@ static void mvebu_uart_console_write(struct console *co, const char *s, uart_console_write(port, s, count, mvebu_uart_console_putchar); - wait_for_xmitr(port); + wait_for_xmite(port); if (ier) writel(ier, port->membase + UART_CTRL(port)); -- cgit v1.2.3 From 1f1496a923b6ba16679074fe77100e1b53cdb880 Mon Sep 17 00:00:00 2001 From: Damien Le Moal Date: Sun, 13 Dec 2020 22:50:35 +0900 Subject: riscv: Fix sifive serial driver Setup the port uartclk in sifive_serial_probe() so that the base baud rate is correctly printed during device probe instead of always showing "0". I.e. the probe message is changed from 38000000.serial: ttySIF0 at MMIO 0x38000000 (irq = 1, base_baud = 0) is a SiFive UART v0 to the correct: 38000000.serial: ttySIF0 at MMIO 0x38000000 (irq = 1, base_baud = 115200) is a SiFive UART v0 Signed-off-by: Damien Le Moal Reviewed-by: Palmer Dabbelt Acked-by: Palmer Dabbelt Signed-off-by: Palmer Dabbelt --- drivers/tty/serial/sifive.c | 1 + 1 file changed, 1 insertion(+) (limited to 'drivers/tty') diff --git a/drivers/tty/serial/sifive.c b/drivers/tty/serial/sifive.c index 1066eebe3b28..328d5a78792f 100644 --- a/drivers/tty/serial/sifive.c +++ b/drivers/tty/serial/sifive.c @@ -1000,6 +1000,7 @@ static int sifive_serial_probe(struct platform_device *pdev) /* Set up clock divider */ ssp->clkin_rate = clk_get_rate(ssp->clk); ssp->baud_rate = SIFIVE_DEFAULT_BAUD_RATE; + ssp->port.uartclk = ssp->baud_rate * 16; __ssp_update_div(ssp); platform_set_drvdata(pdev, ssp); -- cgit v1.2.3 From a91bd6223ecd46addc71ee6fcd432206d39365d2 Mon Sep 17 00:00:00 2001 From: Petr Mladek Date: Fri, 8 Jan 2021 12:48:47 +0100 Subject: Revert "init/console: Use ttynull as a fallback when there is no console" This reverts commit 757055ae8dedf5333af17b3b5b4b70ba9bc9da4e. The commit caused that ttynull was used as the default console on several systems[1][2][3]. As a result, the console was blank even when a better alternative existed. It happened when there was no console configured on the command line and ttynull_init() was the first initcall calling register_console(). Or it happened when /dev/ did not exist when console_on_rootfs() was called. It was not able to open /dev/console even though a console driver was registered. It tried to add ttynull console but it obviously did not help. But ttynull became the preferred console and was used by /dev/console when it was available later. The commit tried to fix a historical problem that have been there for ages. The primary motivation was the commit 3cffa06aeef7ece30f6 ("printk/console: Allow to disable console output by using console="" or console=null"). It provided a clean solution for a workaround that was widely used and worked only by chance. This revert causes that the console="" or console=null command line options will again work only by chance. These options will cause that a particular console will be preferred and the default (tty) ones will not get enabled. There will be no console registered at all. As a result there won't be stdin, stdout, and stderr for the init process. But it worked exactly this way even before. The proper solution has to fulfill many conditions: + Register ttynull only when explicitly required or as the ultimate fallback. + ttynull should get associated with /dev/console but it must not become preferred console when used as a fallback. Especially, it must still be possible to replace it by a better console later. Such a change requires clean up of the register_console() code. Otherwise, it would be even harder to follow. Especially, the use of has_preferred_console and CON_CONSDEV flag is tricky. The clean up is risky. The ordering of consoles is not well defined. And any changes tend to break existing user settings. Do the revert at the least risky solution for now. [1] https://lore.kernel.org/linux-kselftest/20201221144302.GR4077@smile.fi.intel.com/ [2] https://lore.kernel.org/lkml/d2a3b3c0-e548-7dd1-730f-59bc5c04e191@synopsys.com/ [3] https://patchwork.ozlabs.org/project/linux-um/patch/20210105120128.10854-1-thomas@m3y3r.de/ Reported-by: Andy Shevchenko Reported-by: Vineet Gupta Reported-by: Thomas Meyer Signed-off-by: Petr Mladek Acked-by: Greg Kroah-Hartman Acked-by: Sergey Senozhatsky Signed-off-by: Linus Torvalds --- drivers/tty/Kconfig | 14 ++++++++++++++ drivers/tty/Makefile | 3 ++- drivers/tty/ttynull.c | 18 ------------------ include/linux/console.h | 3 --- init/main.c | 10 ++-------- 5 files changed, 18 insertions(+), 30 deletions(-) (limited to 'drivers/tty') diff --git a/drivers/tty/Kconfig b/drivers/tty/Kconfig index 47a6e42f0d04..e15cd6b5bb99 100644 --- a/drivers/tty/Kconfig +++ b/drivers/tty/Kconfig @@ -401,6 +401,20 @@ config MIPS_EJTAG_FDC_KGDB_CHAN help FDC channel number to use for KGDB. +config NULL_TTY + tristate "NULL TTY driver" + help + Say Y here if you want a NULL TTY which simply discards messages. + + This is useful to allow userspace applications which expect a console + device to work without modifications even when no console is + available or desired. + + In order to use this driver, you should redirect the console to this + TTY, or boot the kernel with console=ttynull. + + If unsure, say N. + config TRACE_ROUTER tristate "Trace data router for MIPI P1149.7 cJTAG standard" depends on TRACE_SINK diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile index 3c1c5a9240a7..b3ccae932660 100644 --- a/drivers/tty/Makefile +++ b/drivers/tty/Makefile @@ -2,7 +2,7 @@ obj-$(CONFIG_TTY) += tty_io.o n_tty.o tty_ioctl.o tty_ldisc.o \ tty_buffer.o tty_port.o tty_mutex.o \ tty_ldsem.o tty_baudrate.o tty_jobctrl.o \ - n_null.o ttynull.o + n_null.o obj-$(CONFIG_LEGACY_PTYS) += pty.o obj-$(CONFIG_UNIX98_PTYS) += pty.o obj-$(CONFIG_AUDIT) += tty_audit.o @@ -25,6 +25,7 @@ obj-$(CONFIG_ISI) += isicom.o obj-$(CONFIG_MOXA_INTELLIO) += moxa.o obj-$(CONFIG_MOXA_SMARTIO) += mxser.o obj-$(CONFIG_NOZOMI) += nozomi.o +obj-$(CONFIG_NULL_TTY) += ttynull.o obj-$(CONFIG_ROCKETPORT) += rocket.o obj-$(CONFIG_SYNCLINK_GT) += synclink_gt.o obj-$(CONFIG_PPC_EPAPR_HV_BYTECHAN) += ehv_bytechan.o diff --git a/drivers/tty/ttynull.c b/drivers/tty/ttynull.c index eced70ec54e1..17f05b7eb6d3 100644 --- a/drivers/tty/ttynull.c +++ b/drivers/tty/ttynull.c @@ -2,13 +2,6 @@ /* * Copyright (C) 2019 Axis Communications AB * - * The console is useful for userspace applications which expect a console - * device to work without modifications even when no console is available - * or desired. - * - * In order to use this driver, you should redirect the console to this - * TTY, or boot the kernel with console=ttynull. - * * Based on ttyprintk.c: * Copyright (C) 2010 Samo Pogacnik */ @@ -66,17 +59,6 @@ static struct console ttynull_console = { .device = ttynull_device, }; -void __init register_ttynull_console(void) -{ - if (!ttynull_driver) - return; - - if (add_preferred_console(ttynull_console.name, 0, NULL)) - return; - - register_console(&ttynull_console); -} - static int __init ttynull_init(void) { struct tty_driver *driver; diff --git a/include/linux/console.h b/include/linux/console.h index dbe78e8e2602..20874db50bc8 100644 --- a/include/linux/console.h +++ b/include/linux/console.h @@ -186,12 +186,9 @@ extern int braille_register_console(struct console *, int index, extern int braille_unregister_console(struct console *); #ifdef CONFIG_TTY extern void console_sysfs_notify(void); -extern void register_ttynull_console(void); #else static inline void console_sysfs_notify(void) { } -static inline void register_ttynull_console(void) -{ } #endif extern bool console_suspend_enabled; diff --git a/init/main.c b/init/main.c index 421640fca375..c68d784376ca 100644 --- a/init/main.c +++ b/init/main.c @@ -1480,14 +1480,8 @@ void __init console_on_rootfs(void) struct file *file = filp_open("/dev/console", O_RDWR, 0); if (IS_ERR(file)) { - pr_err("Warning: unable to open an initial console. Fallback to ttynull.\n"); - register_ttynull_console(); - - file = filp_open("/dev/console", O_RDWR, 0); - if (IS_ERR(file)) { - pr_err("Warning: Failed to add ttynull console. No stdin, stdout, and stderr for the init process!\n"); - return; - } + pr_err("Warning: unable to open an initial console.\n"); + return; } init_dup(file); init_dup(file); -- cgit v1.2.3 From 17749851eb9ca2298e7c3b81aae4228961b36f28 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Thu, 21 Jan 2021 10:04:27 -0800 Subject: tty: fix up hung_up_tty_write() conversion In commit "tty: implement write_iter", I left the write_iter conversion of the hung up tty case alone, because I incorrectly thought it didn't matter. Jiri showed me the errors of my ways, and pointed out the problems with that incomplete conversion. Fix it all up. Reported-by: Jiri Slaby Signed-off-by: Linus Torvalds Reviewed-by: Jiri Slaby Link: https://lore.kernel.org/r/CAHk-=wh+-rGsa=xruEWdg_fJViFG8rN9bpLrfLz=_yBYh2tBhA@mail.gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/tty/tty_io.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) (limited to 'drivers/tty') diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c index 502862626b2b..4a208a95e921 100644 --- a/drivers/tty/tty_io.c +++ b/drivers/tty/tty_io.c @@ -437,8 +437,7 @@ static ssize_t hung_up_tty_read(struct file *file, char __user *buf, return 0; } -static ssize_t hung_up_tty_write(struct file *file, const char __user *buf, - size_t count, loff_t *ppos) +static ssize_t hung_up_tty_write(struct kiocb *iocb, struct iov_iter *from) { return -EIO; } @@ -504,7 +503,7 @@ static const struct file_operations console_fops = { static const struct file_operations hung_up_tty_fops = { .llseek = no_llseek, .read = hung_up_tty_read, - .write = hung_up_tty_write, + .write_iter = hung_up_tty_write, .poll = hung_up_tty_poll, .unlocked_ioctl = hung_up_tty_ioctl, .compat_ioctl = hung_up_tty_compat_ioctl, @@ -1044,7 +1043,9 @@ static ssize_t tty_write(struct kiocb *iocb, struct iov_iter *from) if (tty->ops->write_room == NULL) tty_err(tty, "missing write_room method\n"); ld = tty_ldisc_ref_wait(tty); - if (!ld || !ld->ops->write) + if (!ld) + return hung_up_tty_write(iocb, from); + if (!ld->ops->write) ret = -EIO; else ret = do_tty_write(ld->ops->write, tty, file, from); -- cgit v1.2.3