Hi,
On Thu, May 28, 2026 at 10:10:50AM +0300, Dmitry Baryshkov wrote:
> If the DisplayPort drivers use display-connector for the HPD detection,
> the internal HPD state machine might be not active and thus the hardware
> might be not able to handle cable detection correctly. Instead it will
> depend on the external HPD notifications to set the cable state,
> bypassing the internal HPD state machine (for example this is the case
> for the msm DP driver).
>
> However if the cable has been plugged before the HPD IRQ has been
> enabled, there will be no HPD event coming. The drivers might fail
> detection in such a case. Trigger the HPD notification after enabling
> the HPD IRQ, propagating the cable insertion state.
>
> Note, this issue only affects drivers which set OP_HPD but not OP_DETECT
> (like dp-connector). Here DP differs from HDMI. For HDMI there is no
> additional state or extra "bridge with no sinks plugged" cases. The HPD
> pin state is equal to the display plugged state. Nor do we have an AUX
> bus with timeouts, etc.
>
> Fixes: 2e2bf3a5584d ("drm/bridge: display-connector: add DP support")
> Reported-by: Yongxing Mou <[email protected]>
> Signed-off-by: Dmitry Baryshkov <[email protected]>
> ---Reviewed-by: Sebastian Reichel <[email protected]> Greetings, -- Sebastian > drivers/gpu/drm/bridge/display-connector.c | 19 +++++++++++++++++++ > 1 file changed, 19 insertions(+) > > diff --git a/drivers/gpu/drm/bridge/display-connector.c > b/drivers/gpu/drm/bridge/display-connector.c > index 6bb1134f75c3..f7a5bfd9c075 100644 > --- a/drivers/gpu/drm/bridge/display-connector.c > +++ b/drivers/gpu/drm/bridge/display-connector.c > @@ -12,6 +12,7 @@ > #include <linux/of.h> > #include <linux/platform_device.h> > #include <linux/regulator/consumer.h> > +#include <linux/workqueue.h> > > #include <drm/drm_atomic_helper.h> > #include <drm/drm_bridge.h> > @@ -25,6 +26,8 @@ struct display_connector { > > struct regulator *supply; > struct gpio_desc *ddc_en; > + > + struct work_struct hpd_work; > }; > > static inline struct display_connector * > @@ -92,15 +95,29 @@ static void display_connector_hpd_enable(struct > drm_bridge *bridge) > struct display_connector *conn = to_display_connector(bridge); > > enable_irq(conn->hpd_irq); > + > + if (conn->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > + schedule_work(&conn->hpd_work); > } > > static void display_connector_hpd_disable(struct drm_bridge *bridge) > { > struct display_connector *conn = to_display_connector(bridge); > > + if (conn->bridge.type == DRM_MODE_CONNECTOR_DisplayPort) > + cancel_work_sync(&conn->hpd_work); > + > disable_irq(conn->hpd_irq); > } > > +static void display_connector_hpd_work(struct work_struct *work) > +{ > + struct display_connector *conn = container_of(work, struct > display_connector, hpd_work); > + struct drm_bridge *bridge = &conn->bridge; > + > + drm_bridge_hpd_notify(bridge, display_connector_detect(bridge)); > +} > + > static const struct drm_edid *display_connector_edid_read(struct drm_bridge > *bridge, > struct drm_connector > *connector) > { > @@ -395,6 +412,8 @@ static int display_connector_probe(struct platform_device > *pdev) > conn->bridge.ops |= DRM_BRIDGE_OP_DETECT; > if (conn->hpd_irq >= 0) > conn->bridge.ops |= DRM_BRIDGE_OP_HPD; > + if (conn->hpd_irq >= 0 && type == DRM_MODE_CONNECTOR_DisplayPort) > + INIT_WORK(&conn->hpd_work, display_connector_hpd_work); > > dev_dbg(&pdev->dev, > "Found %s display connector '%s' %s DDC bus and %s HPD GPIO > (ops 0x%x)\n", > > -- > 2.47.3 >
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