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Old 03-18-2008, 06:54 AM   #1
Registered: Nov 2006
Distribution: Ubuntu Hardy
Posts: 69

Rep: Reputation: 15
Question setserial always results in deadlock when uart specified

I am trying to configure a PC104/16C550 modem which has jumpers to set the port address(8 ports) & irq(from 3 thru 7). The host is an Arcom Viper (PC104, Linux viper #1 Wed Sep 13 11:29:51 BST 2006 armv5tel unknown). This comptuer has 5 serial ports by default:
Serial: 8250/16550 driver $Revision: 1.90 $ 64 ports, IRQ sharing enabled
serial8250.0: ttyS0 at MMIO 0x40100000 (irq = 15) is a XScale
serial8250.0: ttyS1 at MMIO 0x40200000 (irq = 14) is a XScale
serial8250.0: ttyS2 at MMIO 0x40700000 (irq = 13) is a XScale
serial8250.0: ttyS3 at MMIO 0x14300010 (irq = 27) is a XR16850
serial8250.0: ttyS4 at MMIO 0x14300000 (irq = 26) is a XR16850 I set the port to 0x2A8 (6th port) and irq is set as 7 with setserial:

# setserial /dev/ttyS5 baud_base 115200 port 0x2a8 irq 7 uart 16550
but this always results in a deadlock & a lot of debugging info is displayed below
Unable to handle kernel NULL pointer dereference at virtual address 000002aa
pgd = c30b8000
[000002aa] *pgd=a311a031, *pte=00000000, *ppte=00000000
Internal error: Oops: 817 [#1]
Modules linked in: serial_cs isp116x_hcd usbcore pxa2xx_cs pxa2xx_core pcmcia pcmcia_core firmware_class ds1307
CPU: 0
PC is at serial_out+0x78/0x80
LR is at 0x1
pc : [<c00e4f44>]    lr : [<00000001>]    Not tainted
sp : c30a5c40  ip : 00000000  fp : c30a5c4c
r10: 00000000  r9 : 00000000  r8 : 00000001
r7 : 00000000  r6 : c02b112c  r5 : c01c9c38  r4 : 00000000
r3 : 000002a8  r2 : 00000001  r1 : 00000002  r0 : c01c9c38
Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  Segment user
Control: 397F  Table: A30B8000  DAC: 00000015
Process setserial (pid: 718, stack limit = 0xc30a4198)
[<c00e4ecc>] (serial_out+0x0/0x80) from [<c00e5c20>] (serial8250_startup+0xd4/0x3a8)
[<c00e5b4c>] (serial8250_startup+0x0/0x3a8) from [<c00e24a4>] (uart_startup+0xa0/0x19c)
 r6 = C02B112C  r5 = C01C9C38  r4 = C38DFC60 
[<c00e2404>] (uart_startup+0x0/0x19c) from [<c00e3324>] (uart_ioctl+0x5a4/0xa44)
 r8 = BEF30CB8  r7 = 00000000  r6 = C02B112C  r5 = 00000000
 r4 = C01C9C38 
[<c00e2d80>] (uart_ioctl+0x0/0xa44) from [<c00d2c3c>] (tty_ioctl+0xcc0/0xd64)
[<c00d1f7c>] (tty_ioctl+0x0/0xd64) from [<c0076bfc>] (do_ioctl+0x78/0x88)
[<c0076b84>] (do_ioctl+0x0/0x88) from [<c0076e9c>] (vfs_ioctl+0x290/0x2b0)
 r6 = 00000003  r5 = BEF30CB8  r4 = C397D4E0 
[<c0076c0c>] (vfs_ioctl+0x0/0x2b0) from [<c0076efc>] (sys_ioctl+0x40/0x5c)
 r7 = 00000036  r6 = 0000541F  r5 = FFFFFFF7  r4 = C397D4E0
[<c0076ebc>] (sys_ioctl+0x0/0x5c) from [<c0018ce0>] (ret_fast_syscall+0x0/0x2c)
 r6 = BEF30ECA  r5 = 000132DC  r4 = 0000A058 
Code: e5903004 e7832001 e89da800 e5903000 (e7c3e001) 
[ BUG: lock recursion deadlock detected! |

setserial/718 is trying to acquire this lock:
 [c02b1144] {uart_register_driver}
.. held by:         setserial:  718 [c03cd820, 117]
... acquired at:               uart_ioctl+0x1ec/0xa44
... trying at:                 uart_close+0x38/0x1d4
| showing all locks held by: |  (setserial/718 [c03cd820, 117]):

#001:             [c02b1144] {uart_register_driver}
... acquired at:               uart_ioctl+0x1ec/0xa44

Showing all blocking locks in the system:
S            init:    1 [c0284d60, 116] (not blocked on mutex)
S     ksoftirqd/0:    2 [c0284ac0, 134] (not blocked on mutex)
S      watchdog/0:    3 [c0284820,   0] (not blocked on mutex)
S        events/0:    4 [c0284580, 110] (not blocked on mutex)
S         khelper:    5 [c02842e0, 110] (not blocked on mutex)
S         kthread:    6 [c0284040, 115] (not blocked on mutex)
S       kblockd/0:   25 [c02fed60, 120] (not blocked on mutex)
S         pdflush:   48 [c0335040, 120] (not blocked on mutex)
S         pdflush:   49 [c0349d60, 115] (not blocked on mutex)
S           aio/0:   51 [c0349820, 120] (not blocked on mutex)
S         kswapd0:   50 [c0349ac0, 125] (not blocked on mutex)
S       mtdblockd:  200 [c02c02e0, 125] (not blocked on mutex)
S  jffs2_gcd_mtd2:  258 [c03cd040, 135] (not blocked on mutex)
S         pccardd:  482 [c03cd2e0, 115] (not blocked on mutex)
S           khubd:  511 [c02d6ac0, 110] (not blocked on mutex)
S         portmap:  606 [c02c0580, 115] (not blocked on mutex)
S         syslogd:  627 [c02d62e0, 116] (not blocked on mutex)
R           klogd:  630 [c03cd580, 116] (not blocked on mutex)
S       rpc.statd:  635 [c02d6820, 120] (not blocked on mutex)
S           inetd:  662 [c02b3820, 120] (not blocked on mutex)
R          thttpd:  667 [c02c0820, 116] (not blocked on mutex)
S            sshd:  674 [c03ff580, 116] (not blocked on mutex)
S            cron:  679 [c02fe820, 115] (not blocked on mutex)
S           getty:  680 [c3c16d60, 116] (not blocked on mutex)
S            sshd:  681 [c0349580, 115] (not blocked on mutex)
S              sh:  685 [c03492e0, 115] (not blocked on mutex)
R       setserial:  718 [c03cd820, 117] (not blocked on mutex)

I am however able to repeat the above command successfully but I have to exclude the uart option and setserial returns instantly. The settings were verified as being set, however any operation with the port (/dev/ttyS5) results in an I/O error (even a simple cat < /dev/ttyS5).

I've removed all gettys on serial ports...what could be the problem?

Last edited by debuser123; 03-18-2008 at 06:55 AM.
Old 03-27-2008, 01:41 AM   #2
Registered: Nov 2006
Distribution: Ubuntu Hardy
Posts: 69

Original Poster
Rep: Reputation: 15
"Unable to handle kernel NULL pointer dereference at virtual address 000002aa"

This is obviously wrong...because:
1) the physical address of the PC104 bus is @ 0x30000000
2) the virtual address of 0x30000000phys = 0xf1000000 (verified in kernel source [arch=arm, machine=pxa255 w/CONFIG_VIPER=y])
3) the port I had supplied was 0x2a8, so the above info means it was trying to send out a byte at the uart's 3rd register. it did this I guess on testing the uart (skip_test not supplied).

So, I'm making a kernel module that simply maps the resources at the right places. I've got it to map the right locations (0x300002a8 physical for 8 bytes) using serial8250_register_port() which returns line 5.....ttyS5, right?

Except now I just get a Read error when even trying to cat /dev/ttyS5. Is there something I'm missing in order to simply map a port and let the serial8250 driver handle it?

Last edited by debuser123; 03-27-2008 at 01:43 AM.
Old 03-27-2008, 06:31 AM   #3
Registered: Nov 2006
Distribution: Ubuntu Hardy
Posts: 69

Original Poster
Rep: Reputation: 15
I figured it out:
#1 I had to use irq 108 instead of irq 7 because 7 was my "ISA" irq. arch/arm/mach-pxa/viper.c maps ISA irqs to 101+isa_irq with some exceptions.
#2 (this was the main reason it didn't work) the iotype (of the uart_port) had to be set to UPIO_MEM instead of UPIO_PORT. though I knew ARM doesn't have in/out-type instructions I thought the translation would be abstracted and not have to worry about other things. but it was pretty evident that serial_in() was using the port's iobase member (which I had set to the physical address of the 'port' [x300002a8]).

So changing the port .iotype to UPIO_MEM, supplying UPF_BOOT_AUTOCONF | UPF_IOREMAP for the .flags, setting .mapbase to the physical address of the port, and using the ISA-mapped irq worked.

The funny thing is that this board works using an .iotype of UPIO_PORT on a separate computer which is also ARM but a different machine type (ep93xx). However, it's a 2.4 kernel, while the stuff I'm working on is 2.6.

Last edited by debuser123; 03-27-2008 at 06:34 AM.
Old 09-23-2010, 03:59 AM   #4
LQ Newbie
Registered: Sep 2010
Posts: 1

Rep: Reputation: 0
PC/104 serial card on top of Viper

Hi debuser123,
I fall in the same problem as yours. But I don't really understand
what you have done to solve the problem. Did you rebuild the 8250.o
modul kernel or did you rebuild the setserial program.



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