From 37aba16e7943634eb3e5e2e7e850ebb38500d935 Mon Sep 17 00:00:00 2001 From: John Ogness Date: Mon, 21 Sep 2026 16:45:36 +0206 Subject: [PATCH] serial: 8250: Change console_msr_work to IRQ_WORK_LAZY Change console_msr_work (defers MSR handling) to be IRQ_WORK_LAZY, thus not raising an IRQ upon irq_work queueing. The irq_work is then handled on the next kernel tick. This additional delay is acceptable because any pending MSR handling is also performed in the interrupt handler, if mctrl is queried, and during console resume. Using IRQ_WORK_LAZY has the benefit of not needing to raise an IRQ for each line of atomic console printing when modem control is active. On a side note, the Tegra20 and Tegra30 platforms can hang if an irq_work IRQ is raised while entering cpuidle states. This problem was reproducible by performing atomic printing while entering cpuidle. So this change also provides a workaround for these platforms (as long as they are not running tickless). The discussion on this topic is linked below. Link: https://lore.kernel.org/lkml/f3757a75-0ba1-4558-bf57-f19ab7e59a4c@nvidia.com Fixes: d3539347022a ("serial: 8250: Switch to nbcon console, take 2") Signed-off-by: John Ogness Reviewed-by: Petr Mladek Tested-by: Jon Hunter Link: https://patch.msgid.link/20260921143939.170314-1-john.ogness@linutronix.de Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/8250/8250_port.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 38fa45e74a37..1acb73e45f8a 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3597,7 +3597,7 @@ int serial8250_console_setup(struct uart_port *port, char *options, bool probe) up->console_line_ended = true; up->console_msr_work_allow = true; - init_irq_work(&up->console_msr_work, console_msr_handler); + up->console_msr_work = IRQ_WORK_INIT_LAZY(console_msr_handler); if (options) uart_parse_options(options, &baud, &parity, &bits, &flow);