[PATCH v6 17/22] drm: bridge: dw_hdmi: Drop call to drm_bridge_hpd_notify()

[Jonas Karlman]

The use of calls to both drm_helper_hpd_irq_event() and
drm_bridge_hpd_notify() from the HPD IRQ handler may cause multiple
hotplug uevents and modesets when the bridge connector is used.

Use of drm_helper_hpd_irq_event() cause the internal DRM function
check_connector_changed() to be called, which in turn calls the
connector detect()/force() funcs to detect any connection status or
epoch changes, and when changed trigger a hotplug uevent. This also
help ensure that EDID and CEC phys addr is updated.

If only a call drm_bridge_hpd_notify() would be used, a custom connector
status/EDID change detection logic needs to be implemented, to fully
match what check_connector_changed() already provides.

The bridge connector detect() func also ensures that any hpd_notify()
funcs are called for all bridges in the chain, so there is not really
any need to have a call to drm_bridge_hpd_notify() here.

With both calls there is two hotplug uevents, two modesets and a total
of four .hpd_notify() calls (using a bridge connector):

  dw_hdmi_irq(): EVENT=plugout
  drm_helper_hpd_irq_event():
    dw_hdmi_bridge_hpd_notify(status=2)
    [drm:check_connector_changed] [CONNECTOR:46:HDMI-A-1] status updated from connected to disconnected
    [drm:check_connector_changed] [CONNECTOR:46:HDMI-A-1] Changed epoch counter 1 => 2
    [drm:drm_sysfs_connector_hotplug_event] [CONNECTOR:46:HDMI-A-1] generating connector hotplug event
   drm_client_hotplug():
    [drm:drm_fb_helper_hotplug_event]
    [drm:drm_client_modeset_probe]
    [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:46:HDMI-A-1]
    dw_hdmi_bridge_hpd_notify(status=2)
    [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:46:HDMI-A-1] disconnected
    [drm:drm_edid_connector_update] [CONNECTOR:46:HDMI-A-1] EDID changed, epoch counter 3
    [drm:drm_client_modeset_probe] No connectors reported connected with modes
    [drm:drm_client_modeset_probe] [CONNECTOR:46:HDMI-A-1] enabled? no
    [drm:drm_client_firmware_config.isra.0] Not using firmware configuration
    [drm:drm_client_modeset_probe] picking CRTCs for 3840x2160 config
    [drm:drm_client_hotplug] fbdev: ret=0
  drm_bridge_hpd_notify():
    dw_hdmi_bridge_hpd_notify(status=2)
    [drm:drm_sysfs_connector_hotplug_event] [CONNECTOR:46:HDMI-A-1] generating connector hotplug event
   drm_client_hotplug():
    [drm:drm_fb_helper_hotplug_event]
    [drm:drm_client_modeset_probe]
    [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:46:HDMI-A-1]
    dw_hdmi_bridge_hpd_notify(status=2)
    [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:46:HDMI-A-1] disconnected
    [drm:drm_client_modeset_probe] No connectors reported connected with modes
    [drm:drm_client_modeset_probe] [CONNECTOR:46:HDMI-A-1] enabled? no
    [drm:drm_client_firmware_config.isra.0] Not using firmware configuration
    [drm:drm_client_modeset_probe] picking CRTCs for 3840x2160 config
    [drm:drm_client_hotplug] fbdev: ret=0

Change to only call drm_helper_hpd_irq_event() from HPD IRQ handler to
ensure that only one hotplug uevent is sent to userspace when connection
status or EDID changes.

With only a call the drm_helper_hpd_irq_event() there is only a single
hotplug uevent and only two .hpd_notify() calls:

  dw_hdmi_irq(): EVENT=plugout
  drm_helper_hpd_irq_event():
    dw_hdmi_bridge_hpd_notify(status=2)
    [drm:check_connector_changed] [CONNECTOR:46:HDMI-A-1] status updated from connected to disconnected
    [drm:check_connector_changed] [CONNECTOR:46:HDMI-A-1] Changed epoch counter 1 => 2
    [drm:drm_sysfs_connector_hotplug_event] [CONNECTOR:46:HDMI-A-1] generating connector hotplug event
   drm_client_hotplug():
    [drm:drm_fb_helper_hotplug_event]
    [drm:drm_client_modeset_probe]
    [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:46:HDMI-A-1]
    dw_hdmi_bridge_hpd_notify(status=2)
    [drm:drm_helper_probe_single_connector_modes] [CONNECTOR:46:HDMI-A-1] disconnected
    [drm:drm_edid_connector_update] [CONNECTOR:46:HDMI-A-1] EDID changed, epoch counter 3
    [drm:drm_client_modeset_probe] No connectors reported connected with modes
    [drm:drm_client_modeset_probe] [CONNECTOR:46:HDMI-A-1] enabled? no
    [drm:drm_client_firmware_config.isra.0] Not using firmware configuration
    [drm:drm_client_modeset_probe] picking CRTCs for 3840x2160 config
    [drm:drm_client_hotplug] fbdev: ret=0

Tested-by: Diederik de Haas <diederik at cknow-tech.com>  # Rock64, RockPro64, Quartz64-B
Signed-off-by: Jonas Karlman <jonas at kwiboo.se>
---
v6: Drop the call from IRQ handler instead, prior to use of a HPD
    delayed work to avoid a possible deadlock with use of sync() calls
    in the bridge hpd_disable() ops,
    Update commit message,
    Collect t-b tag
v5: New patch
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index e9c4e24c090c..6cc7b2a860bd 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -3101,10 +3101,8 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
 			status == connector_status_connected ?
 			"plugin" : "plugout");
 
-		if (hdmi->bridge.dev) {
+		if (hdmi->bridge.dev)
 			drm_helper_hpd_irq_event(hdmi->bridge.dev);
-			drm_bridge_hpd_notify(&hdmi->bridge, status);
-		}
 	}
 
 	hdmi_writeb(hdmi, intr_stat, HDMI_IH_PHY_STAT0);
-- 
2.54.0