serial: 8250: probe all 16550A variants by default

Message ID
State New
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  • serial: 8250: probe all 16550A variants by default
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Commit Message

Vladimir Oltean May 25, 2020, 1:02 p.m.
From: Vladimir Oltean <>

On NXP T1040, the UART is typically detected as 16550A_FSL64. After said
patch, it gets detected as plain 16550A and the Linux console is
completely garbled and missing characters.

So clearly, introducing the SERIAL_8250_16550A_VARIANTS config option
has broken many existing users because it has changed the default
behavior. Restore that by adding a 'default y' to this option. Users who
care about 20 ms shorter boot time can always disable it, but stop
wasting many debugging hours for people who don't care all that much.

Fixes: dc56ecb81a0a ("serial: 8250: Support disabling mdelay-filled probes of 16550A variants")
Signed-off-by: Vladimir Oltean <>
 drivers/tty/serial/8250/Kconfig | 1 +
 1 file changed, 1 insertion(+)


diff --git a/drivers/tty/serial/8250/Kconfig b/drivers/tty/serial/8250/Kconfig
index af0688156dd0..89c7ecb55619 100644
--- a/drivers/tty/serial/8250/Kconfig
+++ b/drivers/tty/serial/8250/Kconfig
@@ -63,6 +63,7 @@  config SERIAL_8250_PNP
 config SERIAL_8250_16550A_VARIANTS
 	bool "Support for variants of the 16550A serial port"
 	depends on SERIAL_8250
+	default y
 	  The 8250 driver can probe for many variants of the venerable 16550A
 	  serial port. Doing so takes additional time at boot.