1. Not aware of CONFIG_MAGIC_SYSRQ
drivers/tty/serial/imx.c: In function ‘serial_imx_save_context’:
drivers/tty/serial/imx.c:2355:47: error: ‘struct uart_port’ has no member named ‘sysrq’
if (uart_console(&sport->port) && sport->port.sysrq)
And a warning from Geetoo, https://wiki.gentoo.org/wiki/Magic_SysRQ
Warning
Magic SysRq should not be enabled in kernel for production or mission critical systems! Even if Magic SysRq is disabled at boot using for example sysctl, it still leaves /proc/sysrq-trigger open. Not to mention the fact that re-enabling SysRq is as easy as disabling it.
2. console_unlock() takes too long time while registering console in kernal/printk/printk.c
[ 0.392208] 2020000.serial: ttymxc0 at MMIO 0x2020000 (irq = 26, base_baud = 5000000) is a IMX
[ 0.392956] 21e8000.serial: ttymxc1 at MMIO 0x21e8000 (irq = 68, base_baud = 5000000) is a IMX
[ 1.200683] console [ttymxc1] enabled
[ 1.204851] 21ec000.serial: ttymxc2 at MMIO 0x21ec000 (irq = 69, base_baud = 5000000) is a IMX
A similar issue but fixed in 2013: [3/3] printk: Avoid softlockups in console_unlock() - Patchwork
And at least 3 people have the same problem from 2016 to now
4.1.15 BSP register_console issue
https://community.nxp.com/thread/468205
android6.0 imx6q & imx6dl kernel boot very slow （two issue）
https://community.nxp.com/thread/447906
1s time pause on console when kernel boot
https://community.nxp.com/thread/440825
