kernel/drivers/tty/hvc/hvc_dcc.c, branch linux-6.9.y

tty: hvc: convert to u8 and size_t

2023-12-08T11:02:37Z

Switch character types to u8 and sizes to size_t. To conform to characters/sizes in the rest of the tty layer. Signed-off-by: "Jiri Slaby (SUSE)" Cc: Michael Ellerman Cc: Nicholas Piggin Cc: Christophe Leroy Cc: Amit Shah Cc: Arnd Bergmann Cc: Paul Walmsley Cc: Palmer Dabbelt Cc: Albert Ou Cc: linuxppc-dev@lists.ozlabs.org Cc: virtualization@lists.linux.dev Cc: linux-riscv@lists.infradead.org Link: https://lore.kernel.org/r/20231206073712.17776-13-jirislaby@kernel.org Signed-off-by: Greg Kroah-Hartman

tty: hvc: dcc: Check for TXfull condition while setting up early console

2023-12-08T11:02:37Z

Refer ARM DDI 0487I.a ID081822, D17.3.8, DBGDTRTX_EL0, "If TXfull is set to 1, set DTRRX and DTRTX to UNKNOWN" Thus one should always check for TXfull condition before hvc can be used as an early console. This is similar to what is being done today in hvc_dcc_console_init() and hvc_dcc_init(). The count 0x4000000 has been obtained from uboot (v2024.01-rc3) drivers/serial/arm_dcc.c "TIMEOUT_COUNT". It reads the dcc status and waits for 0x4000000 times for the TX Fifo to be available before returning an error. Thus, it will prevent DCC to be used as early console. Signed-off-by: Ayan Kumar Halder Link: https://lore.kernel.org/r/20231205123534.3376883-1-ayan.kumar.halder@amd.com Signed-off-by: Greg Kroah-Hartman

tty: hvc: dcc: Bind driver to CPU core0 for reads and writes

2022-05-05T20:45:57Z

Some external debuggers do not handle reads/writes from/to DCC on secondary cores. Each core has its own DCC device registers, so when a core reads or writes from/to DCC, it only accesses its own DCC device. Since kernel code can run on any core, every time the kernel wants to write to the console, it might write to a different DCC. In SMP mode, external debugger creates multiple windows, and each window shows the DCC output only from that core's DCC. The result is that console output is either lost or scattered across windows. Selecting this debug option will enable code that serializes all console input and output to core 0. The DCC driver will create input and output FIFOs that all cores will use. Reads and writes from/to DCC are handled by a workqueue that runs only core 0. This is a debug feature to be used only in early stage development where debug serial console support would not be present. It disables PM feature like CPU hotplug and is not suitable for production environment. Signed-off-by: Shanker Donthineni Acked-by: Adam Wallis Signed-off-by: Timur Tabi Signed-off-by: Elliot Berman Signed-off-by: Sai Prakash Ranjan Link: https://lore.kernel.org/r/20220428090858.14489-1-quic_saipraka@quicinc.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

hvc: dcc: Add earlycon support

2019-10-11T06:38:07Z

Add DCC earlycon support for early printks. The patch is useful for SoC bringup where HW serial console is broken. Signed-off-by: Michal Simek Link: https://lore.kernel.org/r/41e2920a6348e65b2e986b0e65b66531e87cd756.1570543923.git.michal.simek@xilinx.com Signed-off-by: Greg Kroah-Hartman

tty: hvc: Remove redundant license text

2017-11-08T12:08:12Z

Now that the SPDX tag is in all tty files, that identifies the license in a specific and legally-defined manner. So the extra GPL text wording can be removed as it is no longer needed at all. This is done on a quest to remove the 700+ different ways that files in the kernel describe the GPL license text. And there's unneeded stuff like the address (sometimes incorrect) for the FSF which is never needed. No copyright headers or other non-license-description text was removed. Cc: Jiri Slaby Cc: Paul Mackerras Cc: Michael Ellerman Cc: Chris Metcalf Acked-by: Benjamin Herrenschmidt 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

hvc_dcc: don't ignore errors during initialization

2015-10-04T16:49:27Z

hvc_instantiate() and hvc_alloc() return errors if they fail, so don't ignore them. Signed-off-by: Timur Tabi Signed-off-by: Greg Kroah-Hartman

ARM: tty: Move HVC DCC assembly to arch/arm

2014-05-28T20:33:18Z

Put architecture-specific assembly code where it belongs, allowing for support of additional architectures such as arm64 in the future. Signed-off-by: Christopher Covington Signed-off-by: Greg Kroah-Hartman

TTY: hvc_dcc: probe for a JTAG connection before registering

2013-09-26T01:10:56Z

Enabling the ARM DCC console and using without a JTAG connection will simply hang the system. Since distros like to turn on all options, this is a reoccurring problem to debug. We can do better by checking if anything is attached and handling characters. There is no way to probe this, so send a newline and check that it is handled. Cc: Paolo Pisati Cc: Tim Gardner Cc: Greg Kroah-Hartman Cc: Jiri Slaby Signed-off-by: Rob Herring Signed-off-by: Greg Kroah-Hartman