drm/i915: Check live status before reading edid
The Bspec is very clear that Live status must be checked about before trying to read EDID over DDC channel. This patch makes sure that HDMI EDID is read only when live status is up. The live status doesn't seem to perform very consistent across various platforms when tested with different monitors. The reason behind that is some monitors are late to provide right voltage to set live_status up. So, after getting the interrupt, for a small duration, live status reg fluctuates, and then settles down showing the correct staus. This is explained here in, in a rough way: HPD line ________________ |\ T1 = Monitor Hotplug causing IRQ | \______________________________________ | | | | | | T2 = Live status is stable | | _____________________________________ | | /| Live status _____________|_|/ | | | | | | | | | | T0 T1 T2 (Between T1 and T2 Live status fluctuates or can be even low, depending on the monitor) After several experiments, we have concluded that a max delay of 30ms is enough to allow the live status to settle down with most of the monitors. This total delay of 30ms has been split into a resolution of 3 retries of 10ms each, for the better cases. This delay is kept at 30ms, keeping in consideration that, HDCP compliance expect the HPD handler to respond a plug out in 100ms, by disabling port. v2: Adding checks for VLV/CHV as well. Reusing old ibx and g4x functions to check digital port status. Adding a separate function to get bxt live status (Daniel) v3: Using intel_encoder->hpd_pin to check the live status (Siva) Moving the live status read to intel_hdmi_probe and passing parameter to read/not to read the edid. (me) v4: * Added live status check for all platforms using intel_digital_port_connected. * Rebased on top of Jani's DP cleanup series * Some monitors take time in setting the live status. So retry for few times if this is a connect HPD v5: Removed extra "drm/i915" from commit message. Adding Shashank's sob which was missed. v6: Drop the (!detect_edid && !live_status check) check because for DDI ports which are enumerated as hdmi as well as DP, we don't have a mechanism to differentiate between DP and hdmi inside the encoder's hot_plug. This leads to call to the hdmi's hot_plug hook for DP as well as hdmi which leads to issues during unplug because of the above check. v7: Make intel_digital_port_connected global in this patch, some reformatting of while loop, adding a print when live status is not up. (Rodrigo) v8: Rebase it on nightly which involved skipping the hot_plug hook for now and letting the live_status check happen in detect until the hpd handling part is finalized (Daniel) Signed-off-by: NShashank Sharma <shashank.sharma@intel.com> Signed-off-by: NSonika Jindal <sonika.jindal@intel.com> Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com> Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>
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