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From:   Maxime Ripard <maxime@cerno.tech>
To:     dri-devel@lists.freedesktop.org,
        Daniel Vetter <daniel.vetter@intel.com>,
        David Airlie <airlied@linux.ie>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        Maxime Ripard <maxime@cerno.tech>
Cc:     Maxime Ripard <mripard@kernel.org>, Emma Anholt <emma@anholt.net>,
        Dave Stevenson <dave.stevenson@raspberrypi.com>,
        Boris Brezillon <bbrezillon@kernel.org>,
        Phil Elwell <phil@raspberrypi.com>,
        Tim Gover <tim.gover@raspberrypi.com>,
        Dom Cobley <dom@raspberrypi.com>,
        linux-rpi-kernel@lists.infradead.org,
        Nicolas Saenz Julienne <nsaenz@kernel.org>,
        Hans Verkuil <hverkuil-cisco@xs4all.nl>,
        linux-kernel@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com
Subject: [PATCH v2 5/5] drm/vc4: hdmi: Warn if we access the controller while disabled
Date:   Wed,  7 Jul 2021 11:22:57 +0200
Message-Id: <20210707092257.1465109-6-maxime@cerno.tech>
In-Reply-To: <20210707092257.1465109-1-maxime@cerno.tech>
References: <20210707092257.1465109-1-maxime@cerno.tech>
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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.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 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);
-- 
2.31.1