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[Bug 971091] Re: Pandaboard ES freezes with the default CPU scaling governor ondemand


** Changed in: linaro-ubuntu
       Status: Fix Committed => Fix Released

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  Pandaboard ES freezes with the default CPU scaling governor ondemand

Status in Linaro Texas Instruments Landing Team:
  Fix Released
Status in Linaro Ubuntu Engineering Builds:
  Fix Released
Status in “linux-ti-omap4” package in Ubuntu:
  Fix Released

Bug description:
  Pandaboard ES freezes sporadically with the CPU scaling governor default setting, which is "ondemand". 
  It is a complete freeze, no syslog entry, no serial access, no network, no keyboard/mouse anymore. When pressing the reset button, it will not even reboot. The SD card interface seems to be hanging. Pulling and re-inserting the SD card before pressing the reset button, or a global power-cycle will re-boot the board properly.

  The error occurs during normal operation on desktop, but can also be procuded in an unattended way:
  1. Create a RAM disk by adding this to fstab
       none  /tmp  tmpfs   defaults,noatime,mode=1777,size=600M  0 0
  2. Mount it and create a big file on the RAM disk:
       dd bs=1M count=210 if=/dev/urandom of=/tmp/a
  3. Change to /tmp and start an endless loop:
       while true; do cp a b; date; sleep 3; done

  Note that the "sleep" is important to cause the governor to switch CPU
  speed up and down. Wait for 1 to 8 hrs and find the Pandaboard ES in
  frozen state. You can do the same with a bigger file and /tmp on the
  SD card. This will often produce the error faster (possibly due to CPU
  idling at flash write delays) but will stress your flash card.

  Setting the CPU scaling governor to "performance" completely solves the problem. I guess there might be a HW issue on the Pandaboard ES that kicks in with frequent CPU speed changes. 
  Solution proposal: set the CPU scaling governor to "performance" as default until the issue is further analysed.

  ProblemType: Bug
  DistroRelease: Ubuntu 12.04
  Package: linux-image-3.2.0-1411-omap4 3.2.0-1411.14
  ProcVersionSignature: Ubuntu 3.2.0-1411.14-omap4 3.2.9
  Uname: Linux 3.2.0-1411-omap4 armv7l
  ApportVersion: 1.95-0ubuntu1
  Architecture: armhf
  Date: Sun Apr  1 23:01:52 2012
  SourcePackage: linux-ti-omap4
  UpgradeStatus: No upgrade log present (probably fresh install)

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