linux-kernel - Re: [PATCH] drm/vc4: hdmi: Rely on interrupts to handle hotplug

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Message-ID: <CAPY8ntAqh2wEhN2wO_RQ2jJ7X3ovwB_5UwbrbPypDOhd1KVN6A@mail.gmail.com>
Date:   Wed, 16 Jun 2021 11:09:29 +0100
From:   Dave Stevenson <dave.stevenson@...pberrypi.com>
To:     Maxime Ripard <maxime@...no.tech>
Cc:     DRI Development <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>,
        Eric Anholt <eric@...olt.net>,
        Phil Elwell <phil@...pberrypi.com>,
        Tim Gover <tim.gover@...pberrypi.com>,
        Dom Cobley <dom@...pberrypi.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Daniel Vetter <daniel@...ll.ch>,
        Maxime Ripard <mripard@...nel.org>
Subject: Re: [PATCH] drm/vc4: hdmi: Rely on interrupts to handle hotplug

On Mon, 24 May 2021 at 14:20, Maxime Ripard <maxime@...no.tech> wrote:
>
> DRM currently polls for the HDMI connector status every 10s, which can
> be an issue when we connect/disconnect a display quickly or the device
> on the other end only issues a hotplug pulse (for example on EDID
> change).
>
> Switch the driver to rely on the internal controller logic for the
> BCM2711/RPi4.

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

> Signed-off-by: Maxime Ripard <maxime@...no.tech>
> ---
>  drivers/gpu/drm/vc4/vc4_hdmi.c | 44 ++++++++++++++++++++++++++++++++++
>  1 file changed, 44 insertions(+)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_hdmi.c b/drivers/gpu/drm/vc4/vc4_hdmi.c
> index c27b287d2053..3988969f7410 100644
> --- a/drivers/gpu/drm/vc4/vc4_hdmi.c
> +++ b/drivers/gpu/drm/vc4/vc4_hdmi.c
> @@ -1510,6 +1510,46 @@ static int vc4_hdmi_audio_init(struct vc4_hdmi *vc4_hdmi)
>
>  }
>
> +static irqreturn_t vc4_hdmi_hpd_irq_thread(int irq, void *priv)
> +{
> +       struct vc4_hdmi *vc4_hdmi = priv;
> +       struct drm_device *dev = vc4_hdmi->connector.dev;
> +
> +       if (dev)
> +               drm_kms_helper_hotplug_event(dev);
> +
> +       return IRQ_HANDLED;
> +}
> +
> +static int vc4_hdmi_hotplug_init(struct vc4_hdmi *vc4_hdmi)
> +{
> +       struct platform_device *pdev = vc4_hdmi->pdev;
> +       struct device *dev = &pdev->dev;
> +       int ret;
> +
> +       if (vc4_hdmi->variant->external_irq_controller) {
> +               ret = devm_request_threaded_irq(dev,
> +                                               platform_get_irq_byname(pdev, "hpd-connected"),
> +                                               NULL,
> +                                               vc4_hdmi_hpd_irq_thread, IRQF_ONESHOT,
> +                                               "vc4 hdmi hpd connected", vc4_hdmi);
> +               if (ret)
> +                       return ret;
> +
> +               ret = devm_request_threaded_irq(dev,
> +                                               platform_get_irq_byname(pdev, "hpd-removed"),
> +                                               NULL,
> +                                               vc4_hdmi_hpd_irq_thread, IRQF_ONESHOT,
> +                                               "vc4 hdmi hpd disconnected", vc4_hdmi);
> +               if (ret)
> +                       return ret;
> +
> +               connector->polled = DRM_CONNECTOR_POLL_HPD;
> +       }
> +
> +       return 0;
> +}
> +
>  #ifdef CONFIG_DRM_VC4_HDMI_CEC
>  static irqreturn_t vc4_cec_irq_handler_rx_thread(int irq, void *priv)
>  {
> @@ -2060,6 +2100,10 @@ static int vc4_hdmi_bind(struct device *dev, struct device *master, void *data)
>         if (ret)
>                 goto err_destroy_encoder;
>
> +       ret = vc4_hdmi_hotplug_init(vc4_hdmi);
> +       if (ret)
> +               goto err_destroy_conn;
> +
>         ret = vc4_hdmi_cec_init(vc4_hdmi);
>         if (ret)
>                 goto err_destroy_conn;
> --
> 2.31.1
>