Messages in this thread | | | From | Uli Luckas <> | Subject | Bug in 8250/serial_core suspend code. | Date | Wed, 26 Apr 2006 17:14:48 +0200 |
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Hi, there is a bug in recent kernel's suspend code for serial drivers, at least for 8250 and pxa, probably others though.
When suspending (e.g. apm --suspend) a machine, the serial_core suspend code tries to disable modem control lines (including RTS): http://sosdg.org/~coywolf/lxr/source/drivers/serial/serial_core.c?v=2.6;a=arm#L1926 This is needed to stop the other side of a serial link from sending any data after our serial port has been disabled.
Now in line 1937 ops->shutdown(port) is called. For 8250 this points to serial8250_shutdown, for pxa to serial_pxa_shutdown. Both call xxx__set_mctrl(&up->port, up->port.mctrl) which will restore the old control line values and reverse the intended effect.
I am not quite sure about the right approach to fixing this. Should uart_suspend_port set port.mctrl to 0 after saveing it's old value? Or should serial8250_shutdown simply set port.mctrl to 0?
Please also reply in private mail, as I am not subscribed.
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