[PATCH 2/2] drm/imx: Remove the primary plane created by create_primary_plane()

From: Liu Ying
Date: Wed Nov 04 2015 - 05:10:40 EST

Since we are using ipu_plane_init() to add one primary plane for each
IPU CRTC, it's unnecessary to create the safe one by using the helper

Furthermore, the safe one is attached to crtc->primary, which actually
carries a framebuffer(crtc->primary->fb) created by the fbdev helper to
build up the fbcon. Instead, the one created by ipu_plane_init() is
dangling, but it is the one actually does ipu_plane_mode_set() for the
fbcon. This may causes the mismatch bewteen ipu_plane->enabled(true) and
ipu_plane->base.fb(NULL). Thus, it brings a NULL pointer dereference
issue in ipu_plane_mode_set() when we try to additionally touch the
IDMAC channel of the ipu_plane. This issue could be reproduced by
running the drm modetest with command line 'modetest -P 19:1024x768@XR24'
on the i.MX6Q SabreSD platform(single LVDS display). This patch binds
the plane created by ipu_plane_init() with crtc->primary and removes the
safe one to address this issue.

Signed-off-by: Liu Ying <Ying.Liu@xxxxxxxxxxxxx>
drivers/gpu/drm/imx/imx-drm-core.c | 3 ++-
drivers/gpu/drm/imx/ipuv3-crtc.c | 6 ++++++
2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/imx/imx-drm-core.c b/drivers/gpu/drm/imx/imx-drm-core.c
index 6faa735..08eceeb 100644
--- a/drivers/gpu/drm/imx/imx-drm-core.c
+++ b/drivers/gpu/drm/imx/imx-drm-core.c
@@ -373,7 +373,8 @@ int imx_drm_add_crtc(struct drm_device *drm, struct drm_crtc *crtc,

- drm_crtc_init(drm, crtc,
+ /* The related primary plane will be created in ipu_plane_init(). */
+ drm_crtc_init_with_planes(drm, crtc, NULL, NULL,

return 0;
diff --git a/drivers/gpu/drm/imx/ipuv3-crtc.c b/drivers/gpu/drm/imx/ipuv3-crtc.c
index 8d68697..d27143f 100644
--- a/drivers/gpu/drm/imx/ipuv3-crtc.c
+++ b/drivers/gpu/drm/imx/ipuv3-crtc.c
@@ -343,6 +343,11 @@ err_out:
return ret;

+static inline void ipu_crtc_set_primary_plane(struct ipu_crtc *ipu_crtc)
+ ipu_crtc->base.primary = &ipu_crtc->plane[0]->base;
static int ipu_crtc_init(struct ipu_crtc *ipu_crtc,
struct ipu_client_platformdata *pdata, struct drm_device *drm)
@@ -380,6 +385,7 @@ static int ipu_crtc_init(struct ipu_crtc *ipu_crtc,
goto err_remove_crtc;
+ ipu_crtc_set_primary_plane(ipu_crtc);

/* If this crtc is using the DP, add an overlay plane */
if (pdata->dp >= 0 && pdata->dma[1] > 0) {

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