linux-kernel - [PATCH v2 5/5] drm/vc4: hdmi: Warn if we access the controller while disabled

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Date:   Wed,  7 Jul 2021 11:22:57 +0200
From:   Maxime Ripard <maxime@...no.tech>
To:     dri-devel@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Maxime Ripard <maxime@...no.tech>
Cc:     Maxime Ripard <mripard@...nel.org>, Emma Anholt <emma@...olt.net>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Boris Brezillon <bbrezillon@...nel.org>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>,
        linux-rpi-kernel@...ts.infradead.org,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        linux-kernel@...r.kernel.org, bcm-kernel-feedback-list@...adcom.com
Subject: [PATCH v2 5/5] 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.

Signed-off-by: Maxime Ripard <maxime@...no.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