[alsa-devel] [RFC PATCH] ALSA: hda - Keep power link on for PantherPoint HDMI

David Henningsson david.henningsson at canonical.com
Mon Nov 19 15:14:45 CET 2012

On 11/07/2012 09:36 AM, Takashi Iwai wrote:
> At Wed,  7 Nov 2012 09:22:33 +0100,
> David Henningsson wrote:
>> On some of the PantherPoint HDMI machines we currently enable, we're seeing
>> trouble with unsol events, i e detecting monitor presence, especially when
>> on battery and after suspend/resume.
>> BugLink: https://bugs.launchpad.net/bugs/1075882
>> Tested-by: Cyrus Lien <cyrus.lien at canonical.com>
>> Signed-off-by: David Henningsson <david.henningsson at canonical.com>
>> ---
>>   sound/pci/hda/patch_hdmi.c |    8 ++++++--
>>   1 file changed, 6 insertions(+), 2 deletions(-)
>> So far this is the workaround we have found to be working. Sometimes, it also
>> seems that "cat /proc/asound/cardx/codec#x" can also make the HDMI unsol event
>> trigger, so that the problem fixes itself.
>> We have not run any battery life tests to see if this causes more power consumption.
> Looks safe at least, so I applied to for-next branch to give more
> testing.  If you find a better solution, let me know.

Jesse has now done a battery life test, both for idle machine and S3 
machine, and both with HDMI connected and HDMI unconnected.

All differences in power consumption were within error margins. Given 
that, should we consider sending this patch to stable?

David Henningsson, Canonical Ltd.

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