linux-kernel - [PATCH] drm: imx: Move fbdev setup to before output polling

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Date:   Tue, 17 Nov 2020 16:52:29 +0100
From:   Mark Jonas <mark.jonas@...bosch.com>
To:     Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>
CC:     Pengutronix Kernel Team <kernel@...gutronix.de>,
        NXP Linux Team <linux-imx@....com>,
        <dri-devel@...ts.freedesktop.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>,
        Leo Ruan <tingquan.ruan@...bosch.com>,
        Mark Jonas <mark.jonas@...bosch.com>
Subject: [PATCH] drm: imx: Move fbdev setup to before output polling

From: Leo Ruan <tingquan.ruan@...bosch.com>

The generic fbdev has to be setup before enabling output polling.
Otherwise the fbdev client is not ready to handle delayed events.

Since f53705fd, the generic fbdev is setup after the output polling
init. During fbdev setup, when fbdev probes attached outputs and a
status changes from unknown to connected, the delayed event is
marked and the output_poll_work thread is scheduled without delay.
If output_poll_execute() is runs immediately, the delayed event
is handled without actually polling the output because the fbdev is not
registered yet. So the delayed event is lost. This leads to a dark
screen until a KMS application (or fbcon) sets the screen mode.

This patch fixes the issue by moving the setup of generic fbdev before
initializing and enabling output polling.

Signed-off-by: Leo Ruan <tingquan.ruan@...bosch.com>
Signed-off-by: Mark Jonas <mark.jonas@...bosch.com>
---
 drivers/gpu/drm/imx/imx-drm-core.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
index 9bf5ad6d18a2..2665040e11c7 100644
--- a/drivers/gpu/drm/imx/imx-drm-core.c
+++ b/drivers/gpu/drm/imx/imx-drm-core.c
@@ -240,14 +240,18 @@ static int imx_drm_bind(struct device *dev)
 		legacyfb_depth = 16;
 	}

+	/*
+	 * The generic fbdev has to be setup before enabling output polling.
+	 * Otherwise the fbdev client is not ready to handle delayed events.
+	 */
+	drm_fbdev_generic_setup(drm, legacyfb_depth);
+
 	drm_kms_helper_poll_init(drm);

 	ret = drm_dev_register(drm, 0);
 	if (ret)
 		goto err_poll_fini;

-	drm_fbdev_generic_setup(drm, legacyfb_depth);
-
 	return 0;

 err_poll_fini:
-- 
2.17.1