Re: [PATCH 1/3] drm/omap: Support for HDMI hot plug detection

From: Tomi Valkeinen
Date: Mon May 22 2017 - 07:59:35 EST


On 15/05/17 12:03, Peter Ujfalusi wrote:
> The HPD signal can be used for detecting HDMI cable plug and unplug event
> without the need for polling the status of the line.
> This will speed up detecting such event because we do not need to wait for
> the next poll event to notice the state change.
>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@xxxxxx>
> ---
> drivers/gpu/drm/omapdrm/dss/omapdss.h | 17 +++++++++++++++++
> drivers/gpu/drm/omapdrm/omap_connector.c | 32 +++++++++++++++++++++++++++++++-
> drivers/gpu/drm/omapdrm/omap_drv.c | 29 +++++++++++++++++++++++++++++
> 3 files changed, 77 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/omapdrm/dss/omapdss.h b/drivers/gpu/drm/omapdrm/dss/omapdss.h
> index b19dae1fd6c5..1f01669eb610 100644
> --- a/drivers/gpu/drm/omapdrm/dss/omapdss.h
> +++ b/drivers/gpu/drm/omapdrm/dss/omapdss.h
> @@ -25,6 +25,7 @@
> #include <video/videomode.h>
> #include <linux/platform_data/omapdss.h>
> #include <uapi/drm/drm_mode.h>
> +#include <drm/drm_crtc.h>
>
> #define DISPC_IRQ_FRAMEDONE (1 << 0)
> #define DISPC_IRQ_VSYNC (1 << 1)
> @@ -555,6 +556,14 @@ struct omapdss_hdmi_ops {
> int (*read_edid)(struct omap_dss_device *dssdev, u8 *buf, int len);
> bool (*detect)(struct omap_dss_device *dssdev);
>
> + int (*register_hpd_cb)(struct omap_dss_device *dssdev,
> + void (*cb)(void *cb_data,
> + enum drm_connector_status status),
> + void *cb_data);
> + void (*unregister_hpd_cb)(struct omap_dss_device *dssdev);
> + void (*enable_hpd)(struct omap_dss_device *dssdev);
> + void (*disable_hpd)(struct omap_dss_device *dssdev);
> +
> int (*set_hdmi_mode)(struct omap_dss_device *dssdev, bool hdmi_mode);
> int (*set_infoframe)(struct omap_dss_device *dssdev,
> const struct hdmi_avi_infoframe *avi);
> @@ -761,6 +770,14 @@ struct omap_dss_driver {
> int (*read_edid)(struct omap_dss_device *dssdev, u8 *buf, int len);
> bool (*detect)(struct omap_dss_device *dssdev);
>
> + int (*register_hpd_cb)(struct omap_dss_device *dssdev,
> + void (*cb)(void *cb_data,
> + enum drm_connector_status status),
> + void *cb_data);
> + void (*unregister_hpd_cb)(struct omap_dss_device *dssdev);
> + void (*enable_hpd)(struct omap_dss_device *dssdev);
> + void (*disable_hpd)(struct omap_dss_device *dssdev);
> +
> int (*set_hdmi_mode)(struct omap_dss_device *dssdev, bool hdmi_mode);
> int (*set_hdmi_infoframe)(struct omap_dss_device *dssdev,
> const struct hdmi_avi_infoframe *avi);
> diff --git a/drivers/gpu/drm/omapdrm/omap_connector.c b/drivers/gpu/drm/omapdrm/omap_connector.c
> index c24b6b783e9a..5219e340ed9d 100644
> --- a/drivers/gpu/drm/omapdrm/omap_connector.c
> +++ b/drivers/gpu/drm/omapdrm/omap_connector.c
> @@ -35,6 +35,18 @@ struct omap_connector {
> bool hdmi_mode;
> };
>
> +static void omap_connector_hpd_cb(void *cb_data,
> + enum drm_connector_status status)
> +{
> + struct omap_connector *omap_connector = cb_data;
> + struct drm_connector *connector = &omap_connector->base;
> +
> + if (connector->status != status) {
> + connector->status = status;
> + drm_kms_helper_hotplug_event(omap_connector->base.dev);
> + }
> +}

I'm not sure if this is racy or not... drm_kms_helper_hotplug_event()
should be called without locks held, but is it safe to touch
connector->status without any locks?

> +
> bool omap_connector_get_hdmi_mode(struct drm_connector *connector)
> {
> struct omap_connector *omap_connector = to_omap_connector(connector);
> @@ -75,6 +87,10 @@ static void omap_connector_destroy(struct drm_connector *connector)
> struct omap_dss_device *dssdev = omap_connector->dssdev;
>
> DBG("%s", omap_connector->dssdev->name);
> + if (connector->polled == DRM_CONNECTOR_POLL_HPD &&
> + dssdev->driver->unregister_hpd_cb) {
> + dssdev->driver->unregister_hpd_cb(dssdev);
> + }
> drm_connector_unregister(connector);
> drm_connector_cleanup(connector);
> kfree(omap_connector);
> @@ -216,6 +232,7 @@ struct drm_connector *omap_connector_init(struct drm_device *dev,
> {
> struct drm_connector *connector = NULL;
> struct omap_connector *omap_connector;
> + bool hpd_supported = false;
>
> DBG("%s", dssdev->name);
>
> @@ -233,7 +250,20 @@ struct drm_connector *omap_connector_init(struct drm_device *dev,
> connector_type);
> drm_connector_helper_add(connector, &omap_connector_helper_funcs);
>
> - if (dssdev->driver->detect)
> + if (dssdev->driver->register_hpd_cb) {
> + int ret = dssdev->driver->register_hpd_cb(dssdev,
> + omap_connector_hpd_cb,
> + omap_connector);
> + if (!ret)
> + hpd_supported = true;
> + else if (ret != -ENOTSUPP)
> + DBG("%s: Failed to register HPD callback (%d).",
> + dssdev->name, ret);

This should be an error print, shouldn't it?

Tomi

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