From: James Hughes <james.hughes@raspberrypi.org>
Date: Mon, 29 Jul 2019 11:02:59 +0000 (+0100)
Subject: Fixup FKMS interrupt handing for non-existent display
X-Git-Tag: accepted/tizen/unified/20200709.164653~993
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=fe085d362192d5d1d5e3c70ef6f17a605fdf2bd4;p=platform%2Fkernel%2Flinux-rpi.git

Fixup FKMS interrupt handing for non-existent display

If an errant interrupt flag was received from a non-existent display,
a NULL pointer access was made. Protect against this by checking if a
second display is present prior to checking the interrupt flags.
---

diff --git a/drivers/gpu/drm/vc4/vc4_firmware_kms.c b/drivers/gpu/drm/vc4/vc4_firmware_kms.c
index 653c9f6..14d660a 100644
--- a/drivers/gpu/drm/vc4/vc4_firmware_kms.c
+++ b/drivers/gpu/drm/vc4/vc4_firmware_kms.c
@@ -1087,14 +1087,17 @@ static irqreturn_t vc4_crtc_irq_handler(int irq, void *data)
 				vc4_crtc_handle_page_flip(crtc_list[0]);
 			}
 
-			/* Check for the secondary display too */
-			chan = readl(crtc_list[0]->regs + SMIDSW1);
+			if (crtc_list[1]) {
+				/* Check for the secondary display too */
+				chan = readl(crtc_list[0]->regs + SMIDSW1);
 
-			if (chan & 1) {
-				writel(SMI_NEW, crtc_list[0]->regs + SMIDSW1);
-				if (crtc_list[1]->vblank_enabled)
-					drm_crtc_handle_vblank(&crtc_list[1]->base);
-				vc4_crtc_handle_page_flip(crtc_list[1]);
+				if (chan & 1) {
+					writel(SMI_NEW, crtc_list[0]->regs + SMIDSW1);
+
+					if (crtc_list[1]->vblank_enabled)
+						drm_crtc_handle_vblank(&crtc_list[1]->base);
+					vc4_crtc_handle_page_flip(crtc_list[1]);
+				}
 			}
 		}