Re: [PATCH] Documentation: kernel-parameters.txt Add drm_kms_helper.poll

Am Donnerstag, den 04.10.2012, 13:16 +0200 schrieb Daniel Vetter:

On Thu, Oct 4, 2012 at 12:34 PM, mika.kuoppala@intel.com wrote:

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From: Mika Kuoppala mika.kuoppala@intel.com

Add description for drm_kms_helper.poll module parameter introduced by commit: e58f637bb96d5a0ae0919b9998b891d1ba7e47c9

Commit hashes are hard to remember. Please paste the commit summary too and even better add an URL so people can easily access it when not having a Git clone of Linux around.

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Signed-off-by: Mika Kuoppala mika.kuoppala@intel.com

Actually I've noticed even with just hdmi it stalls for long enough to miss a frame, on an otherwise idle system. Kernel testcases ftw, kms locking ftl :(

Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch

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Documentation/kernel-parameters.txt | 11 +++++++++++ 1 file changed, 11 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index f777fa9..ad97749 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -741,6 +741,17 @@ bytes respectively. Such letter suffixes can also be entirely omitted. if its name and a colon are prepended to the EDID name.

•   drm_kms_helper.poll=
  

•                   Polling for connected VGA devices on older systems
  

•                   can be quite expensive, causing latencies of
  

•                   several hundred milliseconds. This will cause visible
  

•                   stalls, for example in video playback. If you
  

•                   experience stalls in display output occurring every
  

•                   10 seconds (DRM_OUTPUT_POLL_PERIOD=(10*HZ)), disabling
  

•                   polling might help.
  

•                   Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
  

•                   default: enabled
  

So according to Daniel the description should be updated then? For DVI and HDMI polling is not needed unless the connector is wired up incorrectly on the board? Is it right, that VGA also supports auto detection when everything is wired up correctly?

Could you also add advises what people should do? Like, if it is disabled people can still enable the external monitor by running ….

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    dscc4.setup=    [NET]

    dyndbg[="val"]          [KNL,DYNAMIC_DEBUG]

-- 1.7.9.5

Acked-by: Paul Menzel paulepanter@users.sourceforge.net

Thanks,

Paul