linux-kernel - [PATCH 0/2] drm/atomic-helper: Support atomic flush with an optional kthread worker

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Message-Id: <20251031-drm-crtc-flush-worker-v1-0-9edc94da0fb7@nxp.com>
Date: Fri, 31 Oct 2025 18:21:23 +0800
From: Liu Ying <victor.liu@....com>
To: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, 
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, 
 Shawn Guo <shawnguo@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
 Pengutronix Kernel Team <kernel@...gutronix.de>, 
 Fabio Estevam <festevam@...il.com>
Cc: dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
 imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, 
 Liu Ying <victor.liu@....com>
Subject: [PATCH 0/2] drm/atomic-helper: Support atomic flush with an
 optional kthread worker

Hi,

As drm_atomic_helper_commit_planes() calls atomic_flush for CRTCs
sequentially and a driver's atomic_flush callback could be blocking,
the performance for flushing multiple CRTCs in a single atomic commit
could be low, like page flip for multiple CRTCs.  A real case is imx8-dc,
which supports two CRTCs and does atomic_flush in a blocking way, i.e.,
waits for a done event for loading shadow registers.

To resolve that, introduce an optional kthread worker to conduct
flush in drm_atomic_helper_commit_planes(), so that flush can run in
parallel for multiple CRTCs.

Drivers should call drmm_crtc_flush_worker_init() to initialize the
kthread worker if they want to use it.

Patch 1 adds the optional kthread worker support.
Patch 2 makes imx8-dc use the kthread worker.

Let me know your thoughts.  Thanks.

Signed-off-by: Liu Ying <victor.liu@....com>
---
Liu Ying (2):
      drm/atomic-helper: Support atomic flush with an optional kthread worker
      drm/imx: dc-crtc: Use flush worker

 drivers/gpu/drm/drm_atomic_helper.c | 27 ++++++++++++++++-
 drivers/gpu/drm/drm_crtc.c          | 59 +++++++++++++++++++++++++++++++++++++
 drivers/gpu/drm/imx/dc/dc-crtc.c    |  9 +++++-
 include/drm/drm_crtc.h              | 45 ++++++++++++++++++++++++++++
 4 files changed, 138 insertions(+), 2 deletions(-)
---
base-commit: dcb6fa37fd7bc9c3d2b066329b0d27dedf8becaa
change-id: 20251031-drm-crtc-flush-worker-0aac27acf40f

Best regards,
-- 
Liu Ying <victor.liu@....com>