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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        Michael Stapelberg <michael+drm@stapelberg.ch>,
        Maxime Ripard <maxime@cerno.tech>
Subject: [PATCH 5.15 05/32] drm/vc4: hdmi: Make sure the device is powered with CEC
Date:   Fri,  4 Feb 2022 10:22:15 +0100
Message-Id: <20220204091915.421812582@linuxfoundation.org>
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From: Maxime Ripard <maxime@cerno.tech>

Commit 20b0dfa86bef0e80b41b0e5ac38b92f23b6f27f9 upstream.

The original commit depended on a rework commit (724fc856c09e ("drm/vc4:
hdmi: Split the CEC disable / enable functions in two")) that
(rightfully) didn't reach stable.

However, probably because the context changed, when the patch was
applied to stable the pm_runtime_put called got moved to the end of the
vc4_hdmi_cec_adap_enable function (that would have become
vc4_hdmi_cec_disable with the rework) to vc4_hdmi_cec_init.

This means that at probe time, we now drop our reference to the clocks
and power domains and thus end up with a CPU hang when the CPU tries to
access registers.

The call to pm_runtime_resume_and_get() is also problematic since the
.adap_enable CEC hook is called both to enable and to disable the
controller. That means that we'll now call pm_runtime_resume_and_get()
at disable time as well, messing with the reference counting.

The behaviour we should have though would be to have
pm_runtime_resume_and_get() called when the CEC controller is enabled,
and pm_runtime_put when it's disabled.

We need to move things around a bit to behave that way, but it aligns
stable with upstream.

Cc: <stable@vger.kernel.org> # 5.10.x
Cc: <stable@vger.kernel.org> # 5.15.x
Cc: <stable@vger.kernel.org> # 5.16.x
Reported-by: Michael Stapelberg <michael+drm@stapelberg.ch>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c |   25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1738,18 +1738,18 @@ static int vc4_hdmi_cec_adap_enable(stru
 	u32 val;
 	int ret;
 
-	ret = pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev);
-	if (ret)
-		return ret;
+	if (enable) {
+		ret = pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev);
+		if (ret)
+			return ret;
 
-	val = HDMI_READ(HDMI_CEC_CNTRL_5);
-	val &= ~(VC4_HDMI_CEC_TX_SW_RESET | VC4_HDMI_CEC_RX_SW_RESET |
-		 VC4_HDMI_CEC_CNT_TO_4700_US_MASK |
-		 VC4_HDMI_CEC_CNT_TO_4500_US_MASK);
-	val |= ((4700 / usecs) << VC4_HDMI_CEC_CNT_TO_4700_US_SHIFT) |
-	       ((4500 / usecs) << VC4_HDMI_CEC_CNT_TO_4500_US_SHIFT);
+		val = HDMI_READ(HDMI_CEC_CNTRL_5);
+		val &= ~(VC4_HDMI_CEC_TX_SW_RESET | VC4_HDMI_CEC_RX_SW_RESET |
+			 VC4_HDMI_CEC_CNT_TO_4700_US_MASK |
+			 VC4_HDMI_CEC_CNT_TO_4500_US_MASK);
+		val |= ((4700 / usecs) << VC4_HDMI_CEC_CNT_TO_4700_US_SHIFT) |
+			((4500 / usecs) << VC4_HDMI_CEC_CNT_TO_4500_US_SHIFT);
 
-	if (enable) {
 		HDMI_WRITE(HDMI_CEC_CNTRL_5, val |
 			   VC4_HDMI_CEC_TX_SW_RESET | VC4_HDMI_CEC_RX_SW_RESET);
 		HDMI_WRITE(HDMI_CEC_CNTRL_5, val);
@@ -1777,7 +1777,10 @@ static int vc4_hdmi_cec_adap_enable(stru
 			HDMI_WRITE(HDMI_CEC_CPU_MASK_SET, VC4_HDMI_CPU_CEC);
 		HDMI_WRITE(HDMI_CEC_CNTRL_5, val |
 			   VC4_HDMI_CEC_TX_SW_RESET | VC4_HDMI_CEC_RX_SW_RESET);
+
+		pm_runtime_put(&vc4_hdmi->pdev->dev);
 	}
+
 	return 0;
 }
 
@@ -1888,8 +1891,6 @@ static int vc4_hdmi_cec_init(struct vc4_
 	if (ret < 0)
 		goto err_remove_handlers;
 
-	pm_runtime_put(&vc4_hdmi->pdev->dev);
-
 	return 0;
 
 err_remove_handlers: