Messages in this thread | | | Subject | Re: [PATCH] set membase in serial8250_request_port | From | Alex Williamson <> | Date | Mon, 04 Oct 2004 15:43:03 -0600 |
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On Mon, 2004-10-04 at 22:04 +0100, Russell King wrote: > On Mon, Oct 04, 2004 at 12:54:22PM -0600, Alex Williamson wrote: > > > > I'm running into a problem that seems to be caused by this really old > > changeset: > > > > http://linux.bkbits.net:8080/linux-2.5/cset@3d9f67f2BWvXiLsZCFwD-8s_E9AN6A > > > > When I run 'setserial /dev/ttyS1 uart 16450' on an ia64 system w/ MMIO > > UARTs, I get a NAT consumption oops from the kernel. The problem is > > that this code path calls serial8250_release_port() where the membase > > gets cleared. However, the subsequent call to serial8250_request_port() > > doesn't restore membase, causing a read from a bad address. I don't see > > many users of the UPF_IOREMAP flag, so I think the solution is to simply > > make the remap case symmetric to the unmap case. Patch below. Thanks, > > Mostly correct reasoning, but the solution is wrong. Consider what > happens if we call request_port where we have set mapbase and pre- > initialised membase for a memory mapped port (eg, PCI card.) > > This would cause us to re-ioremap the mapbase, which is wrong. We > must obey the UPF_IOREMAP flag here. Note also that this fix you're > reverting will break 8250 for PPC people... > > Could you give further information about the problem you're seeing? > Bear in mind that I know precisely zero about ia64 oopsen so you'll > probably have to explain it to me in detail.
Sure. I've see the problem on any MMIO UART on my box:
# cat /proc/tty/driver/serial serinfo:1.0 driver revision: 0: uart:16550A mmio:0xFF5E0000 irq:49 tx:5327 rx:67 RTS|CTS|DTR|DSR|CD 1: uart:16550A mmio:0xFF5E2000 irq:66 tx:0 rx:0 2: uart:16550A mmio:0xF8031000 irq:64 tx:0 rx:0 3: uart:16550A mmio:0xF8030000 irq:64 tx:0 rx:0 4: uart:16550A mmio:0xF8030010 irq:64 tx:0 rx:0 5: uart:16550A mmio:0xF8030038 irq:64 tx:0 rx:0
The first 2 are dangling off a platform bus, not on PCI. They're discovered via the 8250_acpi code (or the first one may be found via the pcdp setup). The last 4 are in PCI space and handled by 8250_pci.
Using setserial to poke the uart type on a devices produces something like this:
# setserial /dev/ttyS2 uart 16450 setserial[1540]: NaT consumption 17179869216 [1] Modules linked in:
Pid: 1540, CPU 1, comm: setserial psr : 0000101008026018 ifs : 8000000000000002 ip : [<a0000001003035a0>] Not tainted ip is at __ia64_readb+0x0/0x20 unat: 0000000000000000 pfs : 0000000000000389 rsc : 0000000000000003 rnat: e0000001004ac458 bsps: e0000001004ac668 pr : 0a40000000169969 ldrs: 0000000000000000 ccv : 0000000000000202 fpsr: 0009804c0270033f csd : 0000000000000000 ssd : 0000000000000000 b0 : a0000001003ab670 b6 : a000000100002d70 b7 : a0000001003035a0 f6 : 1003e6db6db6db6db6db7 f7 : 000000000000000000000 f8 : 1003e000000000000ef6a f9 : 1003e0000000000068be6 f10 : 1003e0000000051eb851f f11 : 1003e0000000000080000 r1 : a000000100ad35a0 r2 : 0000000000000000 r3 : a000000100a7da6b r8 : a000000100a7da6a r9 : 0000000000000006 r10 : a000000100662cd0 r11 : 0000000000000002 r12 : e00000003bf27d70 r13 : e00000003bf20000 r14 : 0000000000000002 r15 : a000000100a7db55 r16 : 0000000000000002 r17 : a0000001008d6d60 r18 : 0000000000008f46 r19 : 0000000000000000 r20 : a0000001006bff58 r21 : a0000001003035a0 r22 : 0000000000000000 r23 : 0000000000000005 r24 : a0000001008eabb0 r25 : a000000100a7da58 r26 : a0000001008eaac0 r27 : a0000001008eaac0 r28 : e00000003bf27d88 r29 : e00000000310d028 r30 : 0000000000000001 r31 : e00000003bf27d84
Call Trace: [<a0000001000168e0>] show_stack+0x80/0xa0 sp=e00000003bf278c0 bsp=e00000003bf21310 [<a000000100017140>] show_regs+0x7e0/0x800 sp=e00000003bf27a90 bsp=e00000003bf212b0 [<a00000010003a8b0>] die+0x150/0x1c0 sp=e00000003bf27aa0 bsp=e00000003bf21270 [<a00000010003a960>] die_if_kernel+0x40/0x60 sp=e00000003bf27aa0 bsp=e00000003bf21240 [<a00000010003b570>] ia64_fault+0x150/0xa40 sp=e00000003bf27aa0 bsp=e00000003bf211f0 [<a00000010000e7e0>] ia64_leave_kernel+0x0/0x260 sp=e00000003bf27ba0 bsp=e00000003bf211f0 [<a0000001003035a0>] __ia64_readb+0x0/0x20 sp=e00000003bf27d70 bsp=e00000003bf211e0 [<a0000001003ab670>] serial_in+0x210/0x220 sp=e00000003bf27d70 bsp=e00000003bf211a8 [<a0000001003aea60>] serial8250_startup+0xc0/0x740 sp=e00000003bf27d70 bsp=e00000003bf21170 [<a0000001003a3900>] uart_startup+0x240/0x440 sp=e00000003bf27d70 bsp=e00000003bf21120 [<a0000001003a55d0>] uart_set_info+0x3f0/0xb40 sp=e00000003bf27d90 bsp=e00000003bf21038 [<a0000001003a70b0>] uart_ioctl+0x2f0/0x3a0 sp=e00000003bf27e20 bsp=e00000003bf20fe8 [<a000000100370500>] tty_ioctl+0x780/0xa20 sp=e00000003bf27e20 bsp=e00000003bf20f90 [<a00000010014c430>] sys_ioctl+0x270/0x720 sp=e00000003bf27e20 bsp=e00000003bf20f00 [<a00000010000e660>] ia64_ret_from_syscall+0x0/0x20 sp=e00000003bf27e30 bsp=e00000003bf20f00
I instrumented serial_in/serial_out to see what what happening (this time for ttyS1):
# setserial /dev/ttyS1 uart 16450 serial_out() -> writeb(0x1, 0xc0000000ff5e2002) serial_out() -> writeb(0x7, 0xc0000000ff5e2002) serial_out() -> writeb(0x0, 0xc0000000ff5e2002) serial_in() -> readb(0xc0000000ff5e2005) serial_in() -> readb(0xc0000000ff5e2000) serial_in() -> readb(0xc0000000ff5e2002) serial_in() -> readb(0xc0000000ff5e2006) serial_in() -> readb(0xc0000000ff5e2005) serial_out() -> writeb(0x3, 0xc0000000ff5e2003) serial_out() -> writeb(0x8, 0xc0000000ff5e2004) serial_out() -> writeb(0x5, 0xc0000000ff5e2001) serial_in() -> readb(0xc0000000ff5e2005) serial_in() -> readb(0xc0000000ff5e2000) serial_in() -> readb(0xc0000000ff5e2002) serial_in() -> readb(0xc0000000ff5e2006) serial_out() -> writeb(0x5, 0xc0000000ff5e2001) serial_out() -> writeb(0x93, 0xc0000000ff5e2003) serial_out() -> writeb(0xc, 0xc0000000ff5e2000) serial_out() -> writeb(0x0, 0xc0000000ff5e2001) serial_out() -> writeb(0x13, 0xc0000000ff5e2003) serial_out() -> writeb(0x1, 0xc0000000ff5e2002) serial_out() -> writeb(0x81, 0xc0000000ff5e2002) serial_out() -> writeb(0x8, 0xc0000000ff5e2004) serial_out() -> writeb(0xb, 0xc0000000ff5e2004) serial_out() -> writeb(0x8, 0xc0000000ff5e2004) serial_out() -> writeb(0x0, 0xc0000000ff5e2001) serial_out() -> writeb(0x0, 0xc0000000ff5e2004) serial_in() -> readb(0xc0000000ff5e2003) serial_out() -> writeb(0x13, 0xc0000000ff5e2003) serial_out() -> writeb(0x1, 0xc0000000ff5e2002) serial_out() -> writeb(0x7, 0xc0000000ff5e2002) serial_out() -> writeb(0x0, 0xc0000000ff5e2002) serial_in() -> readb(0xc0000000ff5e2000) serial_in() -> readb(0x5)
As you can see, we completely lost membase between the last 2 reads and are only dealing with the offset. This is what causes the stack trace in the readb(). I suspect a PCI MMIO UART would fail just as badly on other architectures as well. Is PPC somehow dependent on the UPF_IOREMAP flag, or would it be sufficient to check that membase is NULL before calling ioremap? I see exactly one instance of a driver setting UPF_IOREMAP, which is why I took the path I did. Thanks,
Alex
-- Alex Williamson HP Linux & Open Source Lab
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