misc/162620: SATA device lost when changing brightness on Lenovo L420

[Sebastian Chmielewski]

>Number:         162620
>Category:       misc
>Synopsis:       SATA device lost when changing brightness on Lenovo L420
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    freebsd-bugs
>State:          open
>Quarter:        
>Keywords:       
>Date-Required:
>Class:          sw-bug
>Submitter-Id:   current-users
>Arrival-Date:   Wed Nov 16 20:50:10 UTC 2011
>Closed-Date:
>Last-Modified:
>Originator:     Sebastian Chmielewski
>Release:        9.0-PRERELEASE
>Organization:
>Environment:
FreeBSD xxxx 9.0-PRERELEASE FreeBSD 9.0-PRERELEASE #0: Mon Nov 14 22:51:15 CET 2011     root at xxx:/usr/obj/.../GENERIC  amd64

>Description:
command
sudo sysctl dev.acpi_ibm.0.lcd_brightness=3

or a sequence of two changes:
sudo sysctl dev.acpi_ibm.0.lcd_brightness=6 
sudo sysctl dev.acpi_ibm.0.lcd_brightness=3

cause device disconnect:

ahcich1: DISCONNECT requested
ahcich1: AHCI reset...
ahcich1: SATA connect timeout time=10000us status=00000000
ahcich1: AHCI reset: device not found
(ada1:ahcich1:0:0:0): lost device
(pass1:ahcich1:0:0:0): lost device
(pass1:ahcich1:0:0:0): removing device entry

This problem didn't occur on the same machine with 9.0-CURRENT (before -BETA1 I think).
>How-To-Repeat:

>Fix:


>Release-Note:
>Audit-Trail:
>Unformatted: