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Re: Debugging DRM on a laptop?

On Sun, 5 Aug 2018, wrote:

Hi folks,

we're working on a drmkms update.
I'm testing it on a Dell XPS 9550. It's a laptop with a Skylake CPU.
It has a power button. The power button powers off, not reboot.
This means the dmesg buffer gets wiped.
No serial console as far as I know.

Now it reaches a point where the screen changes, but my DDB_COMMANDENTER
containing "reboot" won't do the expected thing. It's possible it's
hanging. I can't seem to blindly enter ddb.

Any suggestions to make debugging less painful?
Something like arm a watchdog to panic after some time.

I'm gonna experiment with sprinkling panic("XXX"); and see if this works

Can't you tell DDB to 'reboot 0x100' to force a crash dump? Then the message buffer should be saved in the dump file.

| Paul Goyette     | PGP Key fingerprint:     | E-mail addresses:          |
| (Retired)        | FA29 0E3B 35AF E8AE 6651 | paul at whooppee dot com   |
| Kernel Developer | 0786 F758 55DE 53BA 7731 | pgoyette at netbsd dot org |

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