openwrt/target/linux/bcm27xx/patches-5.15/950-0003-drm-vc4-hdmi-Warn-if-we-access-the-controller-while-.patch

From d0a44f399526a061e74b9a34b554f3d0e9cdddb3 Mon Sep 17 00:00:00 2001
From: Maxime Ripard <maxime@cerno.tech>
Date: Thu, 19 Aug 2021 15:59:31 +0200
Subject: [PATCH] drm/vc4: hdmi: Warn if we access the controller while
 disabled

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
---
 drivers/gpu/drm/vc4/vc4_hdmi_regs.h | 6 ++++++
 1 file changed, 6 insertions(+)

--- 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
@@ -415,6 +417,8 @@ static inline u32 vc4_hdmi_read(struct v
 	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);
@@ -441,6 +445,8 @@ static inline void vc4_hdmi_write(struct
 	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);