linux-kernel - [PATCH v2 7/7] drm/mediatek: Fix mtk_atomic_complete for runtime

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Date:	Thu, 4 Aug 2016 10:59:57 +0800
From:	Bibby Hsieh <bibby.hsieh@...iatek.com>
To:	David Airlie <airlied@...ux.ie>,
	Matthias Brugger <matthias.bgg@...il.com>,
	Daniel Vetter <daniel.vetter@...ll.ch>,
	<dri-devel@...ts.freedesktop.org>,
	<linux-mediatek@...ts.infradead.org>
CC:	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	Cawa Cheng <cawa.cheng@...iatek.com>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Bibby Hsieh <bibby.hsieh@...iatek.com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	YT Shen <yt.shen@...iatek.com>,
	Thierry Reding <thierry.reding@...il.com>,
	CK Hu <ck.hu@...iatek.com>, Mao Huang <littlecvr@...omium.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-kernel@...r.kernel.org>,
	Sascha Hauer <kernel@...gutronix.de>
Subject: [PATCH v2 7/7] drm/mediatek: Fix mtk_atomic_complete for runtime_pm

To properly implement atomic w/ runtime pm, we move
drm_atomic_helper_commit_modeset_enables() above
drm_atomic_helper_commit_planes() to ensure CRTCs are enabled before
modifying plane registers, and set active_only to true to filter out
plane update notifications when the CRTC is disabled.

According to the document from linux kernel:
Set the active_only parameters to true in order not to receive plane
update notifications related to a disabled CRTC. This avoids the need
to manually ignore plane updates in driver code when the driver and/or
hardware can't or just don't need to deal with updates on disabled
CRTCs, for example when supporting runtime PM.

Signed-off-by: Bibby Hsieh <bibby.hsieh@...iatek.com>
Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
---
 drivers/gpu/drm/mediatek/mtk_drm_drv.c |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
index b1223d5..507392a 100644
--- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
+++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
@@ -61,10 +61,25 @@ static void mtk_atomic_complete(struct mtk_drm_private *private,
 
 	mtk_atomic_wait_for_fences(state);
 
+	/*
+	 * Mediatek drm supports runtime PM, so plane registers cannot be
+	 * written when their crtc is disabled.
+	 *
+	 * The comment for drm_atomic_helper_commit states:
+	 *     For drivers supporting runtime PM the recommended sequence is
+	 *
+	 *     drm_atomic_helper_commit_modeset_disables(dev, state);
+	 *     drm_atomic_helper_commit_modeset_enables(dev, state);
+	 *     drm_atomic_helper_commit_planes(dev, state, true);
+	 *
+	 * See the kerneldoc entries for these three functions for more details.
+	 */
 	drm_atomic_helper_commit_modeset_disables(drm, state);
-	drm_atomic_helper_commit_planes(drm, state, false);
 	drm_atomic_helper_commit_modeset_enables(drm, state);
+	drm_atomic_helper_commit_planes(drm, state, true);
+
 	drm_atomic_helper_wait_for_vblanks(drm, state);
+
 	drm_atomic_helper_cleanup_planes(drm, state);
 	drm_atomic_state_free(state);
 }
-- 
1.7.9.5