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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