On 23.05.2022 23:32, Marek Szyprowski wrote: > Hi, > > On 16.05.2022 11:20, Vijaya Krishna Nivarthi wrote: >> For the case of console_suspend disabled, if back to back suspend/resume >> test is executed, at the end of test, sometimes console would appear to >> be frozen not responding to input. This would happen because, during >> resume, rx transactions can come in before system is ready, malfunction >> of rx happens in turn resulting in console appearing to be stuck. >> >> Do a stop_rx in suspend sequence to prevent this. >> >> Signed-off-by: Vijaya Krishna Nivarthi <quic_vnivarth@xxxxxxxxxxx> >> --- >> v4: moved the change to serial core to apply for all drivers >> v3: swapped the order of conditions to be more human readable >> v2: restricted patch to contain only stop_rx in suspend sequence >> v1: intial patch contained 2 additional unrelated changes in vicinity >> --- > > This patch landed recently in linux-next as commit c9d2325cdb92 > ("serial: core: Do stop_rx in suspend path for console if > console_suspend is disabled"). > > Unfortunately it breaks console operation on my test systems after > system suspend/resume cycle if 'no_console_suspend' kernel parameter > is present. System properly resumes from suspend, the console displays > all the messages and even command line prompt, but then doesn't react > on any input. If I remove the 'no_console_suspend' parameter, the > console is again operational after system suspend/resume cycle. Before > this patch it worked fine regardless the 'no_console_suspend' parameter. > > If this matters, the test system is ARM 32bit Samsung Exynos5422-based > Odroid XU3lite board. One more information. This issue can be easily reproduced with QEMU. It happens both on ARM 32bit and ARM 64bit QEMU's 'virt' machines when 'no_console_suspend' is added to kernel's cmdline. > >> drivers/tty/serial/serial_core.c | 11 +++++++++-- >> 1 file changed, 9 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/tty/serial/serial_core.c >> b/drivers/tty/serial/serial_core.c >> index 82a1770..9a85b41 100644 >> --- a/drivers/tty/serial/serial_core.c >> +++ b/drivers/tty/serial/serial_core.c >> @@ -2211,9 +2211,16 @@ int uart_suspend_port(struct uart_driver *drv, >> struct uart_port *uport) >> } >> put_device(tty_dev); >> - /* Nothing to do if the console is not suspending */ >> - if (!console_suspend_enabled && uart_console(uport)) >> + /* >> + * Nothing to do if the console is not suspending >> + * except stop_rx to prevent any asynchronous data >> + * over RX line. Re-start_rx, when required, is >> + * done by set_termios in resume sequence >> + */ >> + if (!console_suspend_enabled && uart_console(uport)) { >> + uport->ops->stop_rx(uport); >> goto unlock; >> + } >> uport->suspended = 1; > > Best regards Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland