[PATCH v2] drm: bridge: dw_hdmi: only trigger hotplug event on link change

[PATCH v2] drm: bridge: dw_hdmi: only trigger hotplug event on link change

[Lucas Stach]

There are two events that signal a real change of the link state: HPD going
high means the sink is newly connected or wants the source to re-read the
EDID, RX sense going low is a indication that the link has been disconnected.

Ignore the other two events that also trigger interrupts, but don't need
immediate attention: HPD going low does not necessarily mean the link has
been lost and should not trigger a immediate read of the status. RX sense
going high also does not require a detect cycle, as HPD going high is the
right point in time to read the EDID.

Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Reviewed-by: Neil Armstrong <narmstrong@baylibre.com> (v1)
---
v2: Take HDMI_PHY_RX_SENSE into account when reporting disconnect
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 25a60eb4d67c..40d8ca37f5bc 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -3096,6 +3096,7 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
 {
 	struct dw_hdmi *hdmi = dev_id;
 	u8 intr_stat, phy_int_pol, phy_pol_mask, phy_stat;
+	enum drm_connector_status status = connector_status_unknown;
 
 	intr_stat = hdmi_readb(hdmi, HDMI_IH_PHY_STAT0);
 	phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
@@ -3134,13 +3135,15 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
 			cec_notifier_phys_addr_invalidate(hdmi->cec_notifier);
 			mutex_unlock(&hdmi->cec_notifier_mutex);
 		}
-	}
 
-	if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
-		enum drm_connector_status status = phy_int_pol & HDMI_PHY_HPD
-						 ? connector_status_connected
-						 : connector_status_disconnected;
+		if (phy_stat & HDMI_PHY_HPD)
+			status = connector_status_connected;
+
+		if (!(phy_stat & (HDMI_PHY_HPD | HDMI_PHY_RX_SENSE)))
+			status = connector_status_disconnected;
+	}
 
+	if (status != connector_status_unknown) {
 		dev_dbg(hdmi->dev, "EVENT=%s\n",
 			status == connector_status_connected ?
 			"plugin" : "plugout");
-- 
2.30.2

Re: [PATCH v2] drm: bridge: dw_hdmi: only trigger hotplug event on link change

[Robert Foss]

On Fri, 26 Aug 2022 at 20:57, Lucas Stach <l.stach@pengutronix.de> wrote:
>
> There are two events that signal a real change of the link state: HPD going
> high means the sink is newly connected or wants the source to re-read the
> EDID, RX sense going low is a indication that the link has been disconnected.
>
> Ignore the other two events that also trigger interrupts, but don't need
> immediate attention: HPD going low does not necessarily mean the link has
> been lost and should not trigger a immediate read of the status. RX sense
> going high also does not require a detect cycle, as HPD going high is the
> right point in time to read the EDID.
>
> Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
> Reviewed-by: Neil Armstrong <narmstrong@baylibre.com> (v1)
> ---
> v2: Take HDMI_PHY_RX_SENSE into account when reporting disconnect
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 25a60eb4d67c..40d8ca37f5bc 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -3096,6 +3096,7 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
>  {
>         struct dw_hdmi *hdmi = dev_id;
>         u8 intr_stat, phy_int_pol, phy_pol_mask, phy_stat;
> +       enum drm_connector_status status = connector_status_unknown;
>
>         intr_stat = hdmi_readb(hdmi, HDMI_IH_PHY_STAT0);
>         phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
> @@ -3134,13 +3135,15 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
>                         cec_notifier_phys_addr_invalidate(hdmi->cec_notifier);
>                         mutex_unlock(&hdmi->cec_notifier_mutex);
>                 }
> -       }
>
> -       if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
> -               enum drm_connector_status status = phy_int_pol & HDMI_PHY_HPD
> -                                                ? connector_status_connected
> -                                                : connector_status_disconnected;
> +               if (phy_stat & HDMI_PHY_HPD)
> +                       status = connector_status_connected;
> +
> +               if (!(phy_stat & (HDMI_PHY_HPD | HDMI_PHY_RX_SENSE)))
> +                       status = connector_status_disconnected;
> +       }
>
> +       if (status != connector_status_unknown) {
>                 dev_dbg(hdmi->dev, "EVENT=%s\n",
>                         status == connector_status_connected ?
>                         "plugin" : "plugout");

Reviewed-by: Robert Foss <robert.foss@linaro.org>

Applied to drm-misc-next.