linux-kernel - [PATCH 4/4] drm/vc4: hdmi: Make sure the device is powered with CEC

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Date:   Tue, 29 Jun 2021 14:57:36 +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:     linux-kernel@...r.kernel.org,
        bcm-kernel-feedback-list@...adcom.com,
        Boris Brezillon <bbrezillon@...nel.org>,
        Emma Anholt <emma@...olt.net>,
        Maxime Ripard <mripard@...nel.org>,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Nicolas Saenz Julienne <nsaenz@...nel.org>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>,
        linux-rpi-kernel@...ts.infradead.org
Subject: [PATCH 4/4] drm/vc4: hdmi: Make sure the device is powered with CEC

Similarly to what we encountered with the detect hook with DRM, nothing
actually prevents any of the CEC callback from being run while the HDMI
output is disabled.

However, this is an issue since any register access to the controller
when it's powered down will result in a silent hang.

Let's make sure we run the runtime_pm hooks when the CEC adapter is
opened and closed by the userspace to avoid that issue.

Fixes: 15b4511a4af6 ("drm/vc4: add HDMI CEC support")
Signed-off-by: Maxime Ripard <maxime@...no.tech>
---
 drivers/gpu/drm/vc4/vc4_hdmi.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
index 3f244027eb58..20cb6e62f7a4 100644
--- a/drivers/gpu/drm/vc4/vc4_hdmi.c
+++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
@@ -1741,6 +1741,11 @@ static int vc4_hdmi_cec_enable(struct cec_adapter *adap)
 	/* clock period in microseconds */
 	const u32 usecs = 1000000 / CEC_CLOCK_FREQ;
 	u32 val = HDMI_READ(HDMI_CEC_CNTRL_5);
+	int ret;
+
+	ret = pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev);
+	if (ret)
+		return ret;
 
 	val &= ~(VC4_HDMI_CEC_TX_SW_RESET | VC4_HDMI_CEC_RX_SW_RESET |
 		 VC4_HDMI_CEC_CNT_TO_4700_US_MASK |
@@ -1784,6 +1789,8 @@ static int vc4_hdmi_cec_disable(struct cec_adapter *adap)
 	HDMI_WRITE(HDMI_CEC_CNTRL_5, HDMI_READ(HDMI_CEC_CNTRL_5) |
 		   VC4_HDMI_CEC_TX_SW_RESET | VC4_HDMI_CEC_RX_SW_RESET);
 
+	pm_runtime_put(&vc4_hdmi->pdev->dev);
+
 	return 0;
 }
 
-- 
2.31.1