[PATCH] drm: mxsfb: Fix NULL pointer dereference crash on unload

[Marek Vasut]

The mxsfb->crtc.funcs may already be NULL when unloading the driver,
in which case calling mxsfb_irq_disable() via drm_irq_uninstall() from
mxsfb_unload() leads to NULL pointer dereference.

Since all we care about is masking the IRQ and mxsfb->base is still
valid, just use that to clear and mask the IRQ.

Fixes: ae1ed00932819 ("drm: mxsfb: Stop using DRM simple display pipeline helper")
Signed-off-by: Marek Vasut <marex at denx.de>
Cc: Daniel Abrecht <public at danielabrecht.ch>
Cc: Emil Velikov <emil.l.velikov at gmail.com>
Cc: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Cc: Sam Ravnborg <sam at ravnborg.org>
Cc: Stefan Agner <stefan at agner.ch>
---
 drivers/gpu/drm/mxsfb/mxsfb_drv.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
index ec0432fe1bdf8..86d78634a9799 100644
--- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
+++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
@@ -173,7 +173,11 @@ static void mxsfb_irq_disable(struct drm_device *drm)
 	struct mxsfb_drm_private *mxsfb = drm->dev_private;
 
 	mxsfb_enable_axi_clk(mxsfb);
-	mxsfb->crtc.funcs->disable_vblank(&mxsfb->crtc);
+
+	/* Disable and clear VBLANK IRQ */
+	writel(CTRL1_CUR_FRAME_DONE_IRQ_EN, mxsfb->base + LCDC_CTRL1 + REG_CLR);
+	writel(CTRL1_CUR_FRAME_DONE_IRQ, mxsfb->base + LCDC_CTRL1 + REG_CLR);
+
 	mxsfb_disable_axi_clk(mxsfb);
 }
 
-- 
2.33.0