[PATCH v2] Documentation: kernel-parameters.txt Add drm_kms_helper.poll

[mika.kuoppala at intel.com]

From: Mika Kuoppala <mika.kuoppala at intel.com>

Possibility to disable polling to find connected displays was
introduced by commit [1]:

commit e58f637bb96d5a0ae0919b9998b891d1ba7e47c9
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Fri Aug 20 09:13:36 2010 +0100

    drm/kms: Add a module parameter to disable polling

Add description for this parameter to kernel-parameters.txt

[1] http://git.kernel.org/?p=linux/kernel/git/torvalds/linux.git;a=commit;h=e58f637bb96d5a0ae0919b9998b891d1ba7e47c9

Signed-off-by: Mika Kuoppala <mika.kuoppala at intel.com>
---
 Documentation/kernel-parameters.txt |   16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index f777fa9..0f0f071 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -741,6 +741,22 @@ 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 display devices on older systems
+			without Hot Plug Detect (HPD) support, can be quite
+			expensive. Poll will happen periodically and can in
+			worst cases take several hundred milliseconds,
+			depending on the hardware. This will cause visible
+			stalls, for example in video playback. These stalls
+			might happen even when your video is on HDP output
+			but you have other non HDP outputs in your hw
+			configuration. If you experience stalls in display
+			output occurring every 10 seconds, disabling polling
+			might help. With polling disabled you need to manually
+			use xrandr to trigger detection.
+			Format: <bool>  (1/Y/y=enable, 0/N/n=disable)
+			default: enabled
+
 	dscc4.setup=	[NET]
 
 	dyndbg[="val"]		[KNL,DYNAMIC_DEBUG]
-- 
1.7.9.5