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References: <20210525091059.234116-1-maxime@cerno.tech> <20210525091059.234116-4-maxime@cerno.tech>
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From:   Dave Stevenson <dave.stevenson@raspberrypi.com>
Date:   Wed, 16 Jun 2021 11:51:26 +0100
Message-ID: <CAPY8ntDfoKLwWG6pkPNvq78C3e5WzXNCVtCykJrrHhZ0UcrjTg@mail.gmail.com>
Subject: Re: [PATCH 3/3] drm/vc4: hdmi: Make sure the controller is powered in detect
To:     Maxime Ripard <maxime@cerno.tech>
Cc:     DRI Development <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>,
        Daniel Vetter <daniel@ffwll.ch>,
        Boris Brezillon <bbrezillon@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Eric Anholt <eric@anholt.net>, Emma Anholt <emma@anholt.net>,
        Phil Elwell <phil@raspberrypi.com>,
        Tim Gover <tim.gover@raspberrypi.com>,
        Dom Cobley <dom@raspberrypi.com>,
        Maxime Ripard <mripard@kernel.org>
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Precedence: bulk

On Tue, 25 May 2021 at 10:11, Maxime Ripard <maxime@cerno.tech> wrote:
>
> If the HPD GPIO is not available and drm_probe_ddc fails, we end up
> reading the HDMI_HOTPLUG register, but the controller might be powered
> off resulting in a CPU hang. Make sure we have the power domain and the
> HSM clock powered during the detect cycle to prevent the hang from
> happening.
>
> Fixes: 4f6e3d66ac52 ("drm/vc4: Add runtime PM support to the HDMI encoder driver")
> Signed-off-by: Maxime Ripard <maxime@cerno.tech>

Reviewed-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 4 ++++
>  1 file changed, 4 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index 867009a471e1..4b6857467e58 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -166,6 +166,8 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
>         struct vc4_hdmi *vc4_hdmi = connector_to_vc4_hdmi(connector);
>         bool connected = false;
>
> +       WARN_ON(pm_runtime_resume_and_get(&vc4_hdmi->pdev->dev));
> +
>         if (vc4_hdmi->hpd_gpio) {
>                 if (gpio_get_value_cansleep(vc4_hdmi->hpd_gpio) ^
>                     vc4_hdmi->hpd_active_low)
> @@ -187,10 +189,12 @@ vc4_hdmi_connector_detect(struct drm_connector *connector, bool force)
>                         }
>                 }
>
> +               pm_runtime_put(&vc4_hdmi->pdev->dev);
>                 return connector_status_connected;
>         }
>
>         cec_phys_addr_invalidate(vc4_hdmi->cec_adap);
> +       pm_runtime_put(&vc4_hdmi->pdev->dev);
>         return connector_status_disconnected;
>  }
>
> --
> 2.31.1
>