Message-ID: <51DBD95C.4060406@googlemail.com>
Date:	Tue, 09 Jul 2013 10:35:24 +0100
From:	Chris Clayton <chris2553@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
CC:	Martin Mokrejs <mmokrejs@...d.natur.cuni.cz>,
	Yijing Wang <wangyijing@...wei.com>,
	Yijing Wang <wangyijing0307@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: 3.8.0-rc4+ - Oops on removing WinTV-HVR-1400 expresscard TV Tuner

Hello again, Bjorn.

On 04/01/13 18:28, Bjorn Helgaas wrote:

<snip>

>>> Hi Chris,
>>>
>>> The current Linux acpiphp driver doesn't do anything unless it finds
>>> devices with _EJ0 or _RMV methods, and your DSDT has neither.  But I
>>> think that implementation is incorrect because I'm not convinced that
>>> those methods are required in order to do hotplug via ACPI.  For
>>> example, your DSDT *does* have an _L01 method that does notifications
>>> to the root ports.  I suspect that hotplug events on your box generate
>>> an SCI that invokes that method.  Linux basically ignores the
>>> resulting notify events, and I suspect that hotplug works on Windows
>>> because it is paying attention to them.
>>>
>>> Can you build a kernel with CONFIG_ACPI_DEBUG=y, do the following, and
>>> attach all the output to the bugzilla?
>>>
>>> 1) Boot with empty ExpressCard slot (without using "pcie_ports=native")
>>> 2) # echo 0x00010004 > /sys/module/acpi/parameters/debug_layer
>>> 3) # echo 0x08000004 > /sys/module/acpi/parameters/debug_level
>>> 4) # lspci -vv
>>> 5) # setpci -s 1c.3 0x42.w
>>> 6) # setpci -s 1c.3 0x5a.w
>>> 7) # setpci -s 1c.3 0xd8.l
>>> 8) Insert ExpressCard
>>> 9) # setpci -s 1c.3 0x5a.w
>>> 10) # dmesg
>>>
>>> Here's what I think we'll see:
>>>
>>> - Slot Implemented (bit 8 of XCAP at 0x42) set, indicating a slot is
>>> implemented below this root port
>>> - Hot Plug SCI Enable (bit 30 of MPC at 0xd8) set, indicating that the
>>> root port should generate an SCI whenever a hotplug event is detected
>>> - Presence Detect State (bit 6 of SLTSTS at 0x5a) change from 0 with
>>> the slot empty to 1 with the slot occupied
>>> - pciehp doing nothing (since _OSC didn't grant the OS permission to
>>> use PCIe native hotplug)
>>> - dmesg indication of the SCI, leading to a Bus Check notification to
>>> \_SB.PCI0.RP04, which is the 1c.3 root port leading to the ExpressCard
>>> slot
>>>
>>
>> As far as I can see, your predicted outcomes where correct. I've added the
>> logs to the bugzilla report.
>
> Yes, it behaved exactly as I expected.  I attached a few more details
> of the analysis to the bug report
> (https://bugzilla.kernel.org/show_bug.cgi?id=54981).  I think we need
> to rework acpiphp to fix this.  We will fix it, but I don't know who
> will do it, or when it will happen.  My list is growing faster than I
> can deal with :(
>

I see that there has been quite a bit of work in the acpiphp area 
recently. Is any of it intended to fix (or ease the subsequent fixing 
of) this bug report, please?

It's not a big deal if it isn't - I do have a system that, via kernel 
command line arguments, recognises expresscard devices when I plug them 
into the slot. But when the release comes along that includes the 
reworking of acpiphp that you mentioned, I will give extra attention to 
hotplugging when I try out the -rc kernels on my laptop.

Thanks

> Thanks very much for your excellent data collection!
>

It's my pleasure!

> Bjorn
>
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