kernel/drivers/tty/serial/apbuart.c, branch linux-6.9.y

serial: apbuart: fix console prompt on qemu

2024-01-04T15:21:06Z

When using a leon kernel with qemu there where no console prompt. The root cause is the handling of the fifo size in the tx part of the apbuart driver. The qemu uart driver only have a very rudimentary status handling and do not report the number of chars queued in the tx fifo in the status register. So the driver ends up with a fifo size of 1. In the tx path the fifo size is divided by 2 - resulting in a fifo size of zero. The original implementation would always try to send one char, but after the introduction of uart_port_tx_limited() the fifo size is respected even for the first char. There seems to be no good reason to divide the fifo size with two - so remove this. It looks like something copied from the original amba driver. With qemu we now have a minimum fifo size of one char, so we show the prompt. Signed-off-by: Sam Ravnborg Fixes: d11cc8c3c4b6 ("tty: serial: use uart_port_tx_limited()") Cc: Andreas Larsson Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: Cc: Link: https://lore.kernel.org/r/20231226121607.GA2622970@ravnborg.org Signed-off-by: Greg Kroah-Hartman

serial: apb: Use port lock wrappers

2023-09-18T09:18:10Z

When a serial port is used for kernel console output, then all modifications to the UART registers which are done from other contexts, e.g. getty, termios, are interference points for the kernel console. So far this has been ignored and the printk output is based on the principle of hope. The rework of the console infrastructure which aims to support threaded and atomic consoles, requires to mark sections which modify the UART registers as unsafe. This allows the atomic write function to make informed decisions and eventually to restore operational state. It also allows to prevent the regular UART code from modifying UART registers while printk output is in progress. All modifications of UART registers are guarded by the UART port lock, which provides an obvious synchronization point with the console infrastructure. To avoid adding this functionality to all UART drivers, wrap the spin_[un]lock*() invocations for uart_port::lock into helper functions which just contain the spin_[un]lock*() invocations for now. In a subsequent step these helpers will gain the console synchronization mechanisms. Converted with coccinelle. No functional change. Signed-off-by: Thomas Gleixner Signed-off-by: John Ogness Link: https://lore.kernel.org/r/20230914183831.587273-19-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman

tty: Explicitly include correct DT includes

2023-07-25T18:19:05Z

The DT of_device.h and of_platform.h date back to the separate of_platform_bus_type before it as merged into the regular platform bus. As part of that merge prepping Arm DT support 13 years ago, they "temporarily" include each other. They also include platform_device.h and of.h. As a result, there's a pretty much random mix of those include files used throughout the tree. In order to detangle these headers and replace the implicit includes with struct declarations, users need to explicitly include the correct includes. Signed-off-by: Rob Herring Acked-by: Uwe Kleine-König # for imx Link: https://lore.kernel.org/r/20230724205440.767071-1-robh@kernel.org Signed-off-by: Greg Kroah-Hartman

serial: drivers: switch ch and flag to u8

2023-07-25T17:21:04Z

Now that the serial layer explicitly expects 'u8' for flags and characters, propagate this type to drivers' (RX) routines. Note that amba-pl011's, clps711x's and st-asc's 'ch' are left unchanged because 'ch' contains not only a character, but whole status. Signed-off-by: Jiri Slaby (SUSE) Cc: Tobias Klauser Cc: Russell King Cc: Vineet Gupta Cc: Richard Genoud Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Claudiu Beznea Cc: Alexander Shiyan Cc: Baruch Siach Cc: "Maciej W. Rozycki" Cc: Taichi Sugaya Cc: Takao Orito Cc: Shawn Guo Cc: Sascha Hauer Cc: Pengutronix Kernel Team Cc: Fabio Estevam Cc: NXP Linux Team Cc: Kevin Cernekee Cc: Krzysztof Kozlowski Cc: Alim Akhtar Cc: Laxman Dewangan Cc: Thierry Reding Cc: Jonathan Hunter Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Orson Zhai Cc: Baolin Wang Cc: Chunyan Zhang Cc: Patrice Chotard Cc: Maxime Coquelin Cc: Alexandre Torgue Cc: Hammer Hsieh Acked-by: Richard GENOUD Acked-by: Tobias Klauser Acked-by: Thierry Reding Acked-by: Maciej W. Rozycki Link: https://lore.kernel.org/r/20230712081811.29004-11-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: serial: use uart_port_tx_limited()

2022-11-03T02:32:40Z

uart_port_tx_limited() is a new helper to send characters to the device. Use it in these drivers. mux.c also needs to define tx_done(). But I'm not sure if the driver really wants to wait for all the characters to dismiss from the HW fifo at this code point. Hence I marked this as FIXME. Cc: Russell King Cc: Florian Fainelli Cc: bcm-kernel-feedback-list@broadcom.com Cc: "Pali Rohár" Cc: Kevin Cernekee Cc: Palmer Dabbelt Cc: Paul Walmsley Cc: Orson Zhai Cc: Baolin Wang Cc: Chunyan Zhang Cc: Patrice Chotard Cc: linux-riscv@lists.infradead.org Reviewed-by: Ilpo Järvinen Signed-off-by: Jiri Slaby (SUSE) Link: https://lore.kernel.org/r/20221004104927.14361-4-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

serial: Make ->set_termios() old ktermios const

2022-08-30T12:22:35Z

There should be no reason to adjust old ktermios which is going to get discarded anyway. Reviewed-by: Andy Shevchenko Signed-off-by: Ilpo Järvinen Link: https://lore.kernel.org/r/20220816115739.10928-7-ilpo.jarvinen@linux.intel.com Signed-off-by: Greg Kroah-Hartman

serial: make uart_console_write->putchar()'s character an unsigned char

2022-03-03T14:06:31Z

Currently, uart_console_write->putchar's second parameter (the character) is of type int. It makes little sense, provided uart_console_write() accepts the input string as "const char *s" and passes its content -- the characters -- to putchar(). So switch the character's type to unsigned char. We don't use char as that is signed on some platforms. That would cause troubles for drivers which (implicitly) cast the char to u16 when writing to the device. Sign extension would happen in that case and the value written would be completely different to the provided char. DZ is an example of such a driver -- on MIPS, it uses u16 for dz_out in dz_console_putchar(). Note we do the char -> uchar conversion implicitly in uart_console_write(). Provided we do not change size of the data type, sign extension does not happen there, so the problem is void. This makes the types consistent and unified with the rest of the uart layer, which uses unsigned char in most places already. One exception is xmit_buf, but that is going to be converted later. Cc: Paul Cercueil Cc: Tobias Klauser Cc: Russell King Cc: Vineet Gupta Cc: Nicolas Ferre Cc: Alexandre Belloni Cc: Ludovic Desroches Cc: Florian Fainelli Cc: bcm-kernel-feedback-list@broadcom.com Cc: Alexander Shiyan Cc: Baruch Siach Cc: "Maciej W. Rozycki" Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: Shawn Guo Cc: Sascha Hauer Cc: Pengutronix Kernel Team Cc: Fabio Estevam Cc: NXP Linux Team Cc: Karol Gugala Cc: Mateusz Holenko Cc: Vladimir Zapolskiy Cc: Neil Armstrong Cc: Kevin Hilman Cc: Jerome Brunet Cc: Martin Blumenstingl Cc: Taichi Sugaya Cc: Takao Orito Cc: Liviu Dudau Cc: Sudeep Holla Cc: Lorenzo Pieralisi Cc: "Andreas Färber" Cc: Manivannan Sadhasivam Cc: Michael Ellerman Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Andy Gross Cc: Bjorn Andersson Cc: Krzysztof Kozlowski Cc: Orson Zhai Cc: Baolin Wang Cc: Chunyan Zhang Cc: Patrice Chotard Cc: Maxime Coquelin Cc: Alexandre Torgue Cc: "David S. Miller" Cc: Peter Korsgaard Cc: Michal Simek Acked-by: Richard Genoud [atmel_serial] Acked-by: Uwe Kleine-König Acked-by: Paul Cercueil Acked-by: Neil Armstrong # meson_serial Signed-off-by: Jiri Slaby Link: https://lore.kernel.org/r/20220303080831.21783-1-jslaby@suse.cz Signed-off-by: Greg Kroah-Hartman

serial: apbuart: drop low-latency workaround

2021-04-22T10:09:25Z

Commit 78d34d75c84d ("tty: serial: apbuart: drop uart_port->lock before calling tty_flip_buffer_push()") claimed to address a locking issue but only provided a dubious lockdep splat from an unrelated driver, which in the end turned out to be due a broken local change carried by the author. Unfortunately these patches were merged before the issue had been analysed properly so the commit messages makes no sense whatsoever. The real issue was first seen on RT which at the time effectively always set the low_latency flag for all serial drivers by patching tty_flip_buffer_push(). This in turn revealed that many drivers did not handle the infamous low_latency behaviour which meant that data was pushed immediately to the line discipline instead of being deferred to a work queue. Since commit a9c3f68f3cd8 ("tty: Fix low_latency BUG"), tty_flip_buffer_push() always schedules a work item to push data to the line discipline and there's no need to keep any low_latency hacks around. Link: https://lore.kernel.org/linux-serial/cover.1376923198.git.viresh.kumar@linaro.org/ Signed-off-by: Johan Hovold Link: https://lore.kernel.org/r/20210421095509.3024-7-johan@kernel.org Signed-off-by: Greg Kroah-Hartman

tty/serial: Migrate apbuart to use has_sysrq

2019-12-18T14:04:44Z

The SUPPORT_SYSRQ ifdeffery is not nice as: - May create misunderstanding about sizeof(struct uart_port) between different objects - Prevents moving functions from serial_core.h - Reduces readability (well, it's ifdeffery - it's hard to follow) In order to remove SUPPORT_SYSRQ, has_sysrq variable has been added. Initialise it in driver's probe and remove ifdeffery. Signed-off-by: Dmitry Safonov Link: https://lore.kernel.org/r/20191213000657.931618-11-dima@arista.com Signed-off-by: Greg Kroah-Hartman

tty: add SPDX identifiers to all remaining files in drivers/tty/

2017-11-08T12:08:12Z

It's good to have SPDX identifiers in all files to make it easier to audit the kernel tree for correct licenses. Update the drivers/tty files files with the correct SPDX license identifier based on the license text in the file itself. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This work is based on a script and data from Thomas Gleixner, Philippe Ombredanne, and Kate Stewart. Cc: Jiri Slaby Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Chris Metcalf Cc: Jiri Kosina Cc: David Sterba Cc: James Hogan Cc: Rob Herring Cc: Eric Anholt Cc: Stefan Wahren Cc: Florian Fainelli Cc: Ray Jui Cc: Scott Branden Cc: bcm-kernel-feedback-list@broadcom.com Cc: "James E.J. Bottomley" Cc: Helge Deller Cc: Joachim Eastwood Cc: Matthias Brugger Cc: Masahiro Yamada Cc: Tobias Klauser Cc: Russell King Cc: Vineet Gupta Cc: Richard Genoud Cc: Alexander Shiyan Cc: Baruch Siach Cc: "Maciej W. Rozycki" Cc: "Uwe Kleine-König" Cc: Pat Gefre Cc: "Guilherme G. Piccoli" Cc: Jason Wessel Cc: Vladimir Zapolskiy Cc: Sylvain Lemieux Cc: Carlo Caione Cc: Kevin Hilman Cc: Liviu Dudau Cc: Sudeep Holla Cc: Lorenzo Pieralisi Cc: Andy Gross Cc: David Brown Cc: "Andreas Färber" Cc: Kevin Cernekee Cc: Laxman Dewangan Cc: Thierry Reding Cc: Jonathan Hunter Cc: Barry Song Cc: Patrice Chotard Cc: Maxime Coquelin Cc: Alexandre Torgue Cc: "David S. Miller" Cc: Peter Korsgaard Cc: Timur Tabi Cc: Tony Prisk Cc: Michal Simek Cc: "Sören Brinkmann" Cc: Thomas Gleixner Cc: Kate Stewart Cc: Philippe Ombredanne Cc: Jiri Slaby Signed-off-by: Greg Kroah-Hartman