5.4-stable review patch. If anyone has any objections, please let me know.
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From: Kaustabh Chakraborty kauschluss@disroot.org
commit b846350aa272de99bf6fecfa6b08e64ebfb13173 upstream.
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: stable@vger.kernel.org Fixes: 96976c3d9aff ("drm/exynos: Add DECON driver") Signed-off-by: Kaustabh Chakraborty kauschluss@disroot.org Signed-off-by: Inki Dae inki.dae@samsung.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/exynos/exynos7_drm_decon.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/gpu/drm/exynos/exynos7_drm_decon.c +++ b/drivers/gpu/drm/exynos/exynos7_drm_decon.c @@ -595,6 +595,10 @@ static irqreturn_t decon_irq_handler(int 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);