Re: kern/46596 (ehci interrupt storm triggered by VGA interrupt)

[Andreas Gustafsson <gson%gson.org@localhost>]

The following reply was made to PR kern/46596; it has been noted by GNATS.

From: Andreas Gustafsson <gson%gson.org@localhost>
To: =?iso-8859-2?Q?Jarom=EDr_Dole=E8ek?= <jaromir.dolecek%gmail.com@localhost>
Cc: "gnats-bugs\@NetBSD.org" <gnats-bugs%netbsd.org@localhost>
Subject: Re: kern/46596 (ehci interrupt storm triggered by VGA interrupt)
Date: Wed, 17 Jun 2020 12:07:18 +0300

 Jaromir,
 
 I dug out the machine from storage and connected a VGA display using a
 passive DVI/VGA adapter plugged into the motherboard DVI port.  My
 test consists of starting a "vmstat 1" and unplugging/replugging the
 adapter from the motherbord DVI port.
 
 I was unable to reproduce the bug using a -current USB live image, so
 apparently it has already been fixed, and as a result, I can't
 meaningfully test your patch.
 
 To narrow down the timeframe of the fix, I tried booting a couple of
 old install CDs and breaking out of sysinst to a shell to run the
 test.  With a 6.1.5 CD, I could reproduce the bug (the vmstat
 interrupt column started showing 200000+ interrupts per second), but
 with a 7.1 install CD, I could not.  Instead, the following kernel
 message was printed:
 
   drm: HPD interrupt storm detected on connector HDMI-A-1: switching from hotplug detection to polling
 
 With the -current live image, there is neither an interrupt store nor
 a kernel message.
 -- 
 Andreas Gustafsson, gson%gson.org@localhost