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Date:      Mon, 01 Jul 2019 12:11:24 +0000
From:      bugzilla-noreply@freebsd.org
To:        bugs@FreeBSD.org
Subject:   [Bug 238037] [PATCH] Implement ig4 suspend/resume
Message-ID:  <bug-238037-227-gS2iybVtKz@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-238037-227@https.bugs.freebsd.org/bugzilla/>
References:  <bug-238037-227@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D238037

--- Comment #8 from Austin Shafer <ashafer@badland.io> ---
(In reply to J.R. Oldroyd from comment #7)

I remember running into this problem while working on this patch. I think I
know what's causing it, but couldn't find a way to fix it. I also don't thi=
nk
it's related to this bug's patch, as it would happen to me when first booti=
ng.

Basically because of the way that the iichid attaches, I think it is possib=
le
for the iichid device to be initialized before the i2c bus. The iichid will=
 try
to read interrupts before they are available and find no data until things =
are
reset.

>From D16698:
"I tried a few approaches to identify and attach an iichid device by queryi=
ng
ACPI directly from the iichid module. That failed on two details: parent
association (in general HID over I2C devices appear below ACPI0 in NewBus b=
ut
it is necessary to have them below the iicbus*/iic* nodes, moving these nod=
e in
NewBus failed for me with a panic) and also interrupt handling (apparently,
interrupts must be handled by the nodes the IRQs are assigned to (i.e. the =
node
below ACPI0). Trying to attach to an IRQ from another node (i.e. a node bel=
ow
iicbus*/i2c*) fails)"

So the iichid is below ACPI0, and I think that gets attached before iicbus.=
 I
have a vague memory of adding printf's to show that this was happening. I'll
try to dig around and see if I have any patches of what I was trying to do =
to
fix this.

I'm no expert on newbus device ordering, so if I'm wrong I'd love an
explanation.

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