From d8851a96ba25d5fa2a3d89550f8333db5b694919 Mon Sep 17 00:00:00 2001 From: Douglas Anderson Date: Thu, 16 Mar 2023 13:20:57 -0700 Subject: [PATCH] tty: serial: qcom-geni-serial: Add a poll_init() function On sc7180 Chromebooks, I did the following: * Didn't enable earlycon in the kernel command line. * Didn't enable serial console in the kernel command line. * Didn't enable an agetty or any other client of "/dev/ttyMSM0". * Added "kgdboc=ttyMSM0" to the kernel command line. After I did that, I tried to enter kdb with this command over an ssh session: echo g > /proc/sysrq-trigger When I did that the system just hung. Although I thought I'd tested this scenario before, I couldn't go back and find a time when it was working. Previous testing must have relied on either the UART acting as the kernel console or an agetty running. It turns out to be pretty easy to fix: we can just use qcom_geni_serial_port_setup() as the .poll_init() function. This, together with the patch ("serial: uart_poll_init() should power on the UART"), allows the debugger to work even if there are no other users of the serial port. Signed-off-by: Douglas Anderson Link: https://lore.kernel.org/r/20230316132027.RESEND.2.Ie678853bb101091afe78cc8c22344bf3ff3aed74@changeid Signed-off-by: Greg Kroah-Hartman --- drivers/tty/serial/qcom_geni_serial.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/tty/serial/qcom_geni_serial.c b/drivers/tty/serial/qcom_geni_serial.c index 28fbc92..1881dd5 100644 --- a/drivers/tty/serial/qcom_geni_serial.c +++ b/drivers/tty/serial/qcom_geni_serial.c @@ -1535,6 +1535,7 @@ static const struct uart_ops qcom_geni_console_pops = { #ifdef CONFIG_CONSOLE_POLL .poll_get_char = qcom_geni_serial_get_char, .poll_put_char = qcom_geni_serial_poll_put_char, + .poll_init = qcom_geni_serial_port_setup, #endif .pm = qcom_geni_serial_pm, }; -- 2.7.4