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i.MX28 Application UART driver mxs-auart module cannot be removed

Question asked by Craig McQueen on Mar 3, 2013
Latest reply on Oct 31, 2014 by Fabio Estevam
Branched to a new discussion

I am adding some hardware handshaking via GPIO lines to the mxs-auart driver. So I am compiling it as a module. I can insert the module fine:

# modprobe mxs_auart

mxs-auart.0: ttySP0 at MMIO 0x8006a000 (irq = 112) is a mxs-auart.0

Found APPUART 3.1.0

mxs-auart.1: ttySP1 at MMIO 0x8006c000 (irq = 113) is a mxs-auart.1

Found APPUART 3.1.0

mxs-auart.2: ttySP2 at MMIO 0x8006e000 (irq = 114) is a mxs-auart.2

Found APPUART 3.1.0



But if I try to remove the module, it gives an error, and also locks up the debug serial port.

# modprobe -r mxs_auart

Trying to free nonexistent resource <000000008006e000-000000008006efff>

Trying to free nonexistent resource <000000008006c000-000000008006cfff>


Any pointers on this? I'm guessing those messages are something to do with the following code:

static void mxs_auart_release_port(struct uart_port *u)


    release_mem_region(u->mapbase, SZ_4K);



But I don't know if that's the root cause of the lock-up. I'm fairly new to Linux kernel device driver programming, and I haven't tried debugging this.