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tty: serial: meson: fix hard LOCKUP on crtscts mode
commit 2a1d728 upstream. There might be hard lockup if we set crtscts mode on port without RTS/CTS configured: # stty -F /dev/ttyAML6 crtscts; echo 1 > /dev/ttyAML6; echo 2 > /dev/ttyAML6 [ 95.890386] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks: [ 95.890857] rcu: 3-...0: (201 ticks this GP) idle=e33c/1/0x4000000000000000 softirq=5844/5846 fqs=4984 [ 95.900212] rcu: (detected by 2, t=21016 jiffies, g=7753, q=296 ncpus=4) [ 95.906972] Task dump for CPU 3: [ 95.910178] task:bash state:R running task stack:0 pid:205 ppid:1 flags:0x00000202 [ 95.920059] Call trace: [ 95.922485] __switch_to+0xe4/0x168 [ 95.925951] 0xffffff8003477508 [ 95.974379] watchdog: Watchdog detected hard LOCKUP on cpu 3 [ 95.974424] Modules linked in: 88x2cs(O) rtc_meson_vrtc Possible solution would be to not allow to setup crtscts on such port. Tested on S905X3 based board. Fixes: ff7693d ("ARM: meson: serial: add MesonX SoC on-chip uart driver") Cc: stable@vger.kernel.org Signed-off-by: Pavel Krasavin <pkrasavin@imaqliq.com> Reviewed-by: Neil Armstrong <neil.armstrong@linaro.org> Reviewed-by: Dmitry Rokosov <ddrokosov@salutedevices.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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