Messages in this thread | | | Date | Mon, 4 Oct 2004 22:04:19 +0100 | From | Russell King <> | Subject | Re: [PATCH] set membase in serial8250_request_port |
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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.
-- Russell King Linux kernel 2.6 ARM Linux - http://www.arm.linux.org.uk/ maintainer of: 2.6 PCMCIA - http://pcmcia.arm.linux.org.uk/ 2.6 Serial core - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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