From 94baf533b8a3c20b1306a45c51cd8a8f2a9015b8 Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime@cerno.tech>
Date: Thu, 19 Aug 2021 15:59:31 +0200
Subject: drm/vc4: hdmi: Warn if we access the controller while disabled
Git-commit: 14e193b95604182a338e3721385e3d8a56d3c5a8
Patch-mainline: v5.17-rc1
References: jsc#PED-1166 jsc#PED-1168 jsc#PED-1170 jsc#PED-1218 jsc#PED-1220 jsc#PED-1222 jsc#PED-1223 jsc#PED-1225

We've had many silent hangs where the kernel would look like it just
stalled due to the access to one of the HDMI registers while the
controller was disabled.

Add a warning if we're about to do that so that it's at least not silent
anymore.

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://patchwork.freedesktop.org/patch/msgid/20210819135931.895976-7-maxime@cerno.tech
Acked-by: Patrik Jakobsson <pjakobsson@suse.de>
---
 drivers/gpu/drm/vc4/vc4_hdmi_regs.h | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi_regs.h b/drivers/gpu/drm/vc4/vc4_hdmi_regs.h
index 19d2fdc446bc..99dde6e06a37 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi_regs.h
+++ b/drivers/gpu/drm/vc4/vc4_hdmi_regs.h
@@ -1,6 +1,8 @@
 #ifndef _VC4_HDMI_REGS_H_
 #define _VC4_HDMI_REGS_H_
 
+#include <linux/pm_runtime.h>
+
 #include "vc4_hdmi.h"
 
 #define VC4_HDMI_PACKET_STRIDE			0x24
@@ -412,6 +414,8 @@ static inline u32 vc4_hdmi_read(struct vc4_hdmi *hdmi,
 	const struct vc4_hdmi_variant *variant = hdmi->variant;
 	void __iomem *base;
 
+	WARN_ON(!pm_runtime_active(&hdmi->pdev->dev));
+
 	if (reg >= variant->num_registers) {
 		dev_warn(&hdmi->pdev->dev,
 			 "Invalid register ID %u\n", reg);
@@ -438,6 +442,8 @@ static inline void vc4_hdmi_write(struct vc4_hdmi *hdmi,
 	const struct vc4_hdmi_variant *variant = hdmi->variant;
 	void __iomem *base;
 
+	WARN_ON(!pm_runtime_active(&hdmi->pdev->dev));
+
 	if (reg >= variant->num_registers) {
 		dev_warn(&hdmi->pdev->dev,
 			 "Invalid register ID %u\n", reg);
-- 
2.38.1