If there's support for another console device (such as a TTY serial),
the kernel occasionally panics during boot. The panic message and a
relevant snippet of the call stack is as follows:
Unable to handle kernel NULL pointer dereference at virtual address
000000000000000
Call trace:
drm_crtc_handle_vblank+0x10/0x30 (P)
decon_irq_handler+0x88/0xb4
[...]
Otherwise, the panics don't happen. This indicates that it's some sort
of race condition.
Add a check to validate if the drm device can handle vblanks before
calling drm_crtc_handle_vblank() to avoid this.
Cc: sta...@vger.kernel.org
Fixes: 96976c3d9aff ("drm/exynos: Add DECON driver")
Signed-off-by: Kaustabh Chakraborty <kauschl...@disroot.org>
---
drivers/gpu/drm/exynos/exynos7_drm_decon.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/drivers/gpu/drm/exynos/exynos7_drm_decon.c
b/drivers/gpu/drm/exynos/exynos7_drm_decon.c
index
43bcbe2e2917df43d7c2d27a9771e892628dd682..c0c0f23169c993ac315fc8d7bcbd09ea6ec9966a
100644
--- a/drivers/gpu/drm/exynos/exynos7_drm_decon.c
+++ b/drivers/gpu/drm/exynos/exynos7_drm_decon.c
@@ -636,6 +636,10 @@ static irqreturn_t decon_irq_handler(int irq, void *dev_id)
if (!ctx->drm_dev)
goto out;
+ /* check if crtc and vblank have been initialized properly */
+ if (!drm_dev_has_vblank(ctx->drm_dev))
+ goto out;
+
if (!ctx->i80_if) {
drm_crtc_handle_vblank(&ctx->crtc->base);
--
2.49.0
